Greetings and thank you for deciding to participate in these amateur radio lessons I hope you will find them interesting, informative and helpful. My name is Bill and my amateur radio call sign is WA6OHP.
Ham radio has been an exciting part of my life for 50 years. I want to express my appreciation for Mac K6BJV and Jim K6KRL for their help and mentoring so that I could get my license; I also want to acknowledge and Ed W6CC and Vern W6CGJ for proctoring the tests so I could get my early license. Mac, Jim, Ed, and Vern are now silent key but I refuse to let their legacy die by passing on to others what they have passed on to me.
During these 50 years I have helped many to get their amateur radio license by teaching ham radio classes, mentoring individuals, and working as a Volunteer Eliminator. I want to help as many as possible across the United States who would like to get their ham radio license. To accomplish this goal I developed these lessons and placed them in blog format.
Those of you in other countries please understand that it is not that I do not want to help you get your amateur radio license. I would love to help you but I can’t. Every country has different requirements and I only know the requirements here in the United States. I welcome everyone to the study and even if you do live in another nation there should be some information that would help you and I invite you to ask questions about these lessons or any other questions about ham radio.
To get the most out of these lessons make them interactive. By interactive I mean I want your input and questions. If you do not understand something in the lesson e-mail your question to wa6ohp@yahoo.com be sure to include “hamslife” or “Ham’s Life” in the subject line so my spam monster will not eat it. You can also use the comment box at the bottom of each session and ask your question but because I do not check this blog each day it could go missed for a while.
I make mistakes and though I have carefully studied each lesson before publishing it. I do not have a proof reader though I desperately need one. So if you find something you believe to be an error please let me know either by e-mail at the previously mentioned address or comment in the comment section. The test questions below the text are copied directly as they are written in the question pool and some of them are not grammatically correct but I wrote them just as they will appear on the test.
If you have a ham related question or radio related technical question that is not part of the question pool please go to http://hamslife.com and use the comment box to ask your question and I will try to answer your question on that site.
Suppose you took a class and the instructor gave you a list of 396 questions with the answers and told you that the final exam will consist of 35 questions selected from the questions and answers he gave you. If you can visualize that scenario then you can understand exactly what getting your ham radio license requires.
The Technician class question pool consists of 396 questions with answers. The Technician class ham radio test has 35 questions taken out of those 396 questions. The questions on the test will be exactly the same as they are in the question pool. You have to get 26 questions correct to pass the test.
Each lesson will consist of text which will discuss the information you will need for that portion of the technician class amateur radio test. This will be followed by questions from the test pool. The answers to all the questions in a section can be found in the text that precedes the questions. Then at the bottom of the questions I give an answer key to those questions which will look something like this A, B, C, D, A. This means that the answer to question 1 is A and the answer to question 2 is B and so forth.
A letter, a number, a letter, and a number before each question identifies the question’s location in the question pool. The identification looks something like this T1A01. The breakdown of the group goes like this: T technician class, 1 means the first group of questions of that subelement, A the first sub-group of questions, and 01 the first question in that subgroup. A few questions from one sub-group will appear in another subgroup because I thought, for study purposes, the question fit in that group better then it did in its original location.
The lessons do not start out with question T1A01 because the section T1 deals with rules, regulations, definitions, and other things that may prove difficult for some people to remember because they do not understand some of the terms used in the questions: terms such as Frequency, Auxiliary station, meter band, CW, SSB and several others. The Lessons starts with SUBELEMENT T5 – Electrical principles, math for electronics, electronic principles, Ohm’s Law. This way I can introduce you to terms and explain them so when you get to the questions about how the FCC governs their use you will understand what they mean.
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I would appreciate knowing you are out there so please use the comment section of this post and let me know your name or even respond anonymously if you wish.
When you have passed your Technician Class exam please let me know if these lessons helped you.
Monday, July 19, 2010
LESSON 1
SUBELEMENT T5 – Electrical principles, math for electronics, electronic principles, Ohm’s Law – [4 Exam Questions - 4 Groups]
Lesson 1a
T5A - Electrical principles; current and voltage, conductors and insulators, alternating and direct current
(If you have not read the introduction please go back and read the introduction before you begin lesson 1.)
Before we start while learning about electronics I want to challenge each of you to try to dismiss from your thinking the relative terms big, little, large, small, fast, and slow. We may consider a race horse fast unless we compare it to a race car and that race car can not be considered fast when compared to the speed of a super sonic aircraft. As we study electricity and electronics if you try to compare speed, size, or numbers to the physical world you can see and touch it may hinder your ability to comprehend.
Some of these lessons use physical illustrations to help you understand but try not to get so wrapped up into the illustration that you get lost in the difference because I assure you the difference exceed the similarities.
You do not have to completely understand all of the physics behind the principles of electronics presented in these lessons to pass the technician class ham radio test. You can you can, and I hope you will, do a much deeper study and learn more as time goes by. For now you only have to understand enough to answer the questions on the test. I have tried to limit these lessons to just the information you need to pass the test.
As you start these studies think of an atom. Almost everyone today knows what an atom looks like even though we can not see them. It has a nucleus composed of protons and neutrons. Electrons orbit the nucleus.
The electrons have a negative charge and the protons have a positive charge. The term negative and positive do not have great significance beyond showing us that they are opposites.
Remember opposites attract and like repel. So electrons move away from other electrons while they move toward protons. Protons don’t move.
When an electron jumps out of its orbit it leaves that atom with more protons then electrons. That atom will then have a positive charge. Electricity is simply the movement of electrons. The medium through which electrons flow is usually a conductor.
The electrons in the atoms of copper, silver, aluminum, mercury, and other metals dislodge easily and thus make good conductors of electricity while the atoms in glass, wood, rubber, and many other things do not dislodge from their orbit easily thus they do not readily allow electrons to flow through them and are called insulators.
Electrons do not move through a conductor the same way as water flows through a pipe but the similarities will help explain some terms and help you remember them.
Flowing water has a current measured in gallons per minuets and electrons flowing through a conductor also have a current, an electrical current, which we measure in Amperes. Water pressure, measured in pounds per square inch, pushes the water to form the current while electrical pressure called Electromotive Force (EMF) or voltage pushes the electrons to form an electrical current. The basic unit of Electromotive Force is the volt.
The voltage and the amperage together determine the power consumed (the rate at which electrical energy is used) by an electrical circuit. The basic unit of electrical power is the watt. (Volts times Amperes equal Watts.)
When the electrons always move in the same direction the circuit is called Direct Current (DC). Remember electrons always move towards a more positive or less negative area so if the more positive area or terminal always remains in the same place the electrons will always flow in the same direction but if the positive terminal moves back and forth on the conductor the electrons will change their direction of flow. When the electrons change direction of flow on regular bases the resulting current flow is then called Alternating Current (AC).
Alternating current like direct current is measured in volts, amperes, and watts. AC has a rate of change called the frequency which needs to be measured. If the pendulum on a clock took one half second to swing from the center position or the very bottom of its swing to the highest position in one direction and come back to the center position and take another half second to swing through to its highest position on the other side of the swing and return to the center position before it starts its new upward movement that complete cycle of the pendulum and we could say the pendulum has a frequency of one cycle per second. Likewise if AC starts from its zero volt point and flows in one direction until it reaches its peak voltage then starts decreasing until it reaches zero volts again followed by a rise in voltage in the other direction to its peak then back down to zero it would have completed one cycle. AC frequency is measured in Hertz (Hz) so one complete cycle per second would equal one Hertz and sixty completed cycle in one second would equal sixty Hertz and so on.
The car battery is one common source of DC voltage with which most of us are familiar while the power source in household plugs is AC. To operate properly radios need a source of Direct Current at the proper operating voltage. Radios that plug directly into the household voltage have an internal circuit called the power supply that changes the AC voltage to proper DC voltage to supply power to the rest of the radio.
The auto industry settled on using 12 volts electrical systems in vehicles with internal combustion engines (the cars most of us drive today.) Most modern mobile transceiver (radio transmitter and receiver combined in one package) are designed to operate directly from the vehicles electrical system thus most mobile transceivers require 12 volts to operate propery. They can double as a base station simply by using a 120 VAC to 12 VDC power supply to supply the proper DC voltage, make sure the power supply has the necessary current capacity needed to transmit.
*T5A01
Electrical current is measured in which of the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes
~~
*T5A02
Electrical power is measured in which of the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes
~~
*T5A03
What is the name for the flow of electrons in an electric circuit?
A. Voltage
B. Resistance
C. Capacitance
D. Current
~~
*T5A04
What is the name for a current that flows only in one direction?
A. Alternating current
B. Direct current
C. Normal current
D. Smooth current
~
*T5A05
What is the electrical term for the electromotive force (EMF) that causes electron flow?
A. Voltage
B. Ampere-hours
C. Capacitance
D. Inductance
~~
*T5A06
How much voltage does a mobile transceiver usually require?
A. About 12 volts
B. About 30 volts
C. About 120 volts
D. About 240 volts
~~
*T5A07
Which of the following is a good electrical conductor?
A. Glass
B. Wood
C. Copper
D. Rubber
~~
*T5A08
Which of the following is a good electrical insulator?
A. Copper
B. Glass
C. Aluminum
D. Mercury
~~
*T5A09
What is the name for a current that reverses direction on a regular basis?
A. Alternating current
B. Direct current
C. Circular current
D. Vertical current
~~
*T5A10
Which term describes the rate at which electrical energy is used?
A. Resistance
B. Current
C. Power
D. Voltage
~~
*T5A11
What is the basic unit of electromotive force?
A. The volt
B. The watt
C. The ampere
D. The ohm
~~
Answers:
D, B, D, B, A, A, C, B, A, C, A
LESSON 1b
T5C - Electronic principles; capacitance, inductance, current flow in circuits, alternating current, definition of RF, power calculations T5D – Ohm’s Law
Water flowing through a pipe experiences opposition to flow do the resistance of the pipe. Electric current flowing through a conductor also experiences opposition to its flow do to electrical friction which is called resistance. The resistance of a circuit is measured in ohms.
If the EMF (voltage) remains constant and the resistance increases the current (number of amperes) will decrease. Likewise if the EMF decreases but the resistance remains constant the current will decrease. An increase in EMF or a decrease in resistance, while the other factor remains constant, will result in current increase.
The relationship between resistance, voltage, and current can be expressed mathematically in a formula we know as Ohm’s law. (Don’t panic it is not a scary as it might sound.) Just remember it takes one volt of electrical pressure to push one ampere of electrical current through one ohm of resistance. Increasing the pressure (EMF) will result in a current increase. If the resistance increases the current will decrease. If we divide the voltage by the resistance we get the current and if we divide the voltage by the current we get the resistance. If we know the current and the resistance we can find the voltage by multiplying the current times the resistance.
E (voltage) = I (current) X R (resistance) I=E/R R=E/I (When writing the formula I is used for intensity or current in amperes, E is used for EMF in volts, and R is used for resistance in ohms.)
So if a resistor has 3 amperes flowing through it and 90 volts across it the value of the resistor equals 90 divided by 3 (volts divided by amperes) which is 30 ohms. A 12 volt circuit with 1.5 amperes flowing has 8 ohms of resistance (12/1.5 = 8). A circuit with a 12 volt source which draws 4 amperes has a resistance of 3 ohms (12/4 = 3).
The current flowing through 80 ohms of resistance with an EMF of 120 volts (120 divided by 80) equals 1.5 amperes. The current flowing through a 100 ohm resistor connected across 200 volts is 2 amperes (200/100 = 2) and the current flowing through a 24 ohm resistor connected across 240 volts is 10 amperes (240/24 = 10).
Finally in our Ohm’s law calculations we need to know that the voltage across a 2 ohm resistor that has 0.5 amperes flowing through it is 1 volt because 2 times 0.5 is 1. The voltage across a 10 ohm resistor that will result in 1 ampere of current is 10 (10 X 1 = 10). A 10 ohm resistor with a current of 2 amperes flowing thought it is 20 volts (10 X 2 = 20).
The power produced by a circuit can be found by multiplying the voltage times the current. Thus a circuit with 13.8 volts DC applied with 10 amperes of current is using 138 watts of power (13.8 X 10 = 138). A circuit with 12 volts applied has 2.5 amperes of current will use 30 watts of power (12 X 2.5 = 30).
When the voltage and the power are the known quantities the current can be calculated by dividing the power by the voltage. Thus when a circuit is using 120 watts when 12 volts is applied the current equals 10 amperes (120/12 = 10).
Whether the circuit is AC or DC the electrical resistance will remain the same but Alternating Current can also have reactance which also oppose the flow of current. Reactance can be either inductive reactance or capacitive reactance. (At this point don’t worry about the term reactance for the test. I only bring it up to help you understand inductance and capacitance which are in the test questions for this lesson.)
Two conductors in close proximity of each other but separated by an insulator have an ability to form an electric field that can store an electrical charge. When the surface area of the conductor is increased or the insulator that separates the conductors is made thinner the amount of energy that can be stored is increased if the voltage remains constant. This ability to store energy in the form of an electric field is called capacitance. A basic unit of capacitance is the farad. The electronic component that utilizes this phenomenon to provide a given level of capacitance to a circuit is called a capacitor.
Electrical energy can also be stored in a magnetic field. When a wire conducts an electrical current it forms a magnetic field around it. A wire wrapped in a coil allows each turn in the coil to interact with the other turns and thus compress the magnetic field it forms in a small area and store energy. The ability to store energy in a magnetic field is called inductance thus the coil of wire used to provide a given amount of inductance can be referred to an inductor or a coil. Inductance is measured in henrys.
In lesson 1a alternating current was compared to the pendulum of a clock. When the pendulum is at its maximum point of swing in one direction it has to stop and start back in the other direction. The pendulum increases in speed as it falls (its kinetic energy increases) until it reaches bottom dead center (kinetic energy is maximum) then it starts to climb the other side and thus loose speed (kinetic energy decreases) until it stops (kinetic energy is zero) at its maximum point of swing and changes direction. The pendulum completes a cycle when it starts and moves to the opposite side and comes completely back to the starting position and moves through to the opposite side and comes back to its starting point.
I know this may seem redundant to what I said earlier but many people seem to have a difficulty in grasping frequency and I want everyone to understand. We can physically observe the frequency of a pendulum and hopefully that will help some grasp the principle of the movement of AC which we can not observe physically. The speed of movement of alternating current remains constant (near the speed of light) but the voltage and amperage rises and falls so the power (energy) will follow the rise and fall of the voltage and current (P=IE) so like the pendulum’s power changes throughout the cycle so does the AC power change through out its cycle. If you use zero volts or zero amperes as the beginning point of an AC cycle the current will then start to flow in a certain direction until it reaches a maximum (which will also be the maximum voltage and power) then the flow will decrease until it reaches zero then the current will start to flow in the other direction until it reaches maximum current flow and the current flow will then start to decrease until it reaches zero so it can change direction. That is one cycle. The number of cycles in a given second is called the frequency and is measured in hertz. So if there are 60 complete cycles in one second that circuit is said to be running at 60 Hertz (abbreviated as 60 Hz)
Alternating Current at high frequencies will create the electromagnetic waves that travel through space we know as radio waves. These radio waves or radio frequencies are frequently abbreviated as RF. All frequencies of radio waves can be referred to as RF.
*T5C01
What is the ability to store energy in an electric field called?
A. Inductance
B. Resistance
C. Tolerance
D. Capacitance
~~
*T5C02
What is the basic unit of capacitance?
A. The farad
B. The ohm
C. The volt
D. The henry
~~
*T5C03
What is the ability to store energy in a magnetic field called?
A. Admittance
B. Capacitance
C. Resistance
D. Inductance
~~
*T5C04
What is the basic unit of inductance?
A. The coulomb
B. The farad
C. The henry
D. The ohm
~~
*T5C05
What is the unit of frequency?
A. Hertz
B. Henry
C. Farad
D. Tesla
~~
*T5C06
What is the abbreviation that refers to radio frequency signals of all types?
A. AF
B. HF
C. RF
D. VHF
~~
*T5C07
What is a usual name for electromagnetic waves that travel through space?
A. Gravity waves
B. Sound waves
C. Radio waves
D. Pressure waves
~~
*T5C08
What is the formula used to calculate electrical power in a DC circuit?
A. Power (P) equals voltage (E) multiplied by current (I)
B. Power (P) equals voltage (E) divided by current (I)
C. Power (P) equals voltage (E) minus current (I)
D. Power (P) equals voltage (E) plus current (I)
~~
*T5C09
How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes?
A. 138 watts
B. 0.7 watts
C. 23.8 watts
D. 3.8 watts
~~
*T5C10
How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes?
A. 4.8 watts
B. 30 watts
C. 14.5 watts
D. 0.208 watts
~~
*T5C11
How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts?
A. 0.1 amperes
B. 10 amperes
C. 12 amperes
D. 132 amperes
~~
Answers: (T5C1 through T5C11)
D, A, D, C, A, C, C, A, A, B, B
*T5D01
What formula is used to calculate current in a circuit?
A. Current (I) equals voltage (E) multiplied by resistance (R)
B. Current (I) equals voltage (E) divided by resistance (R)
C. Current (I) equals voltage (E) added to resistance (R)
D. Current (I) equals voltage (E) minus resistance (R)
~~
*T5D02
What formula is used to calculate voltage in a circuit?
A. Voltage (E) equals current (I) multiplied by resistance (R)
B. Voltage (E) equals current (I) divided by resistance (R)
C. Voltage (E) equals current (I) added to resistance (R)
D. Voltage (E) equals current (I) minus resistance (R)
~~
*T5D03
What formula is used to calculate resistance in a circuit?
A. Resistance (R) equals voltage (E) multiplied by current (I)
B. Resistance (R) equals voltage (E) divided by current (I)
C. Resistance (R) equals voltage (E) added to current (I)
D. Resistance (R) equals voltage (E) minus current (I)
~~
*T5D04
What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts?
A. 3 ohms
B. 30 ohms
C. 93 ohms
D. 270 ohms
~~
*T5D05
What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
A. 18 ohms
B. 0.125 ohms
C. 8 ohms
D. 13.5 ohms
~~
*T5D06
What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
A. 3 ohms
B. 16 ohms
C. 48 ohms
D. 8 Ohms
~~
*T5D07
What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
A. 9600 amperes
B. 200 amperes
C. 0.667 amperes
D. 1.5 amperes
~~
*T5D08
What is the current flowing through a 100-ohm resistor connected across 200 volts?
A. 20,000 amperes
B. 0.5 amperes
C. 2 amperes
D. 100 amperes
~~
*T5D09
What is the current flowing through a 24-ohm resistor connected across 240 volts?
A. 24,000 amperes
B. 0.1 amperes
C. 10 amperes
D. 216 amperes
~~
*T5D10
What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
A. 1 volt
B. 0.25 volts
C. 2.5 volts
D. 1.5 volts
~~
*T5D11
What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
A. 1 volt
B. 10 volts
C. 11 volts
D. 9 volts
~~
*T5D12
What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
A. 8 volts
B. 0.2 volts
C. 12 volts
D. 20 volts
~~
Answers: (T5D1 through T5D12)
B, A, B, B, C, A, D, C, C, A, B, D
LESSON 1c
T5B - Math for electronics; decibels, electrical units and the metric system
Milli and micro are two prefixes commonly seen where the unit being named is less then a whole. Milli equals one thousandth (.001) 500 milliwatts equals 0.5 watts. Micro equals one millionth (.000,001) one microvolt is equal to one one-millionth of a volt. Sometimes whole numbers mixed with decimal numbers will use the milli prefix. An example of a whole number with a decimal number can be seen when writing 1.5 amperes which may also be listed as 1,500 milliamperes. .
If an ammeter (meter used to measure amperes) is calibrated in amperes is used to measure a circuit with 3000 milliamperes the reading would be 3 amperes.
Pico also frequently appears as a prefix but it is usually found in front of farads or the measure of capacitance. A picofarad is equal to one micro-micro-farad or one millionth of one millionth of one farad. Thus 1,000,000 picrofarads is equal to 1 microfarad.
Larger quantities also have prefixes to assist in expressing the quantity. Radio frequencies (remember radio waves are made by high frequency AC so they would be measured in Hertz) are usually listed as kilohertz (1,000 Hertz), megahertz (1,000,000 Hertz), and gigahertz (1,000,000,000 Hertz). They are abbreviated as KHz, MHz, and GHz respectively. Thus another way of expressing a radio signal frequency of 1,500,000 Hertz is 1500 KHz. A frequency readout calibrated in megahertz showing 3.525 MHz could be expressed as 3525 KHz.
A kilo just means one thousand so one kilovolt is equal to one thousand volts.
Mega means one million so one mega watt is equal to one million watts.
Decibels are not actual units they are comparative units. That is they are a way of comparing one power level to another. A full description of decibels can be very complicated and it is not necessary to pass the technician class amateur radio test.
Just try to remember if the power is doubled it is an increase of 3 decibels (abbreviated 3 dB) if the power is increased from 5 watts to 10 watts that is a 3 db change. If the power is decreased four times the changed expressed in decibels is 6 dB (if you have some experience in dB’s you may think what I just said is an error. It may seem like it should be -6 dB but that is not the way it is on the test and just accept that there is a 6 dB difference) so if 12 watts is decreased to 3 watts that is a 6 dB change. If the power difference is ten times then the change expressed in decibels is 10 dB so an increase of power from 20 watts to 200 watts is a 10 dB change.
If the power is doubled it is a 3 dB change.
If the power is decreased four times it is a 6 dB change.
If the power is increased ten times it is a 10 dB change.
That is all you need to know about decibels to pass the test. There are only three questions on decibels in the question pool only one of which might appear on your test.
*T5B01
How many milliamperes is 1.5 amperes?
A. 15 milliamperes
B. 150 milliamperes
C. 1,500 milliamperes
D. 15,000 milliamperes
~~
*T5B02
What is another way to specify a radio signal frequency of 1,500,000 hertz?
A. 1500 kHz
B. 1500 MHz
C. 15 GHz
D. 150 kHz
~~
*T5B03
How many volts are equal to one kilovolt?
A. One one-thousandth of a volt
B. One hundred volts
C. One thousand volts
D. One million volts
~~
*T5B04
How many volts are equal to one microvolt?
A. One one-millionth of a volt
B. One million volts
C. One thousand kilovolts
D. One one-thousandth of a volt
~~
*T5B05
Which of the following is equivalent to 500 milliwatts?
A. 0.02 watts
B. 0.5 watts
C. 5 watts
D. 50 watts
~~
*T5B06
If an ammeter calibrated in amperes is used to measure a 3000-milliampere current, what reading would it show?
A. 0.003 amperes
B. 0.3 amperes
C. 3 amperes
D. 3,000,000 amperes
~~
*T5B07
If a frequency readout calibrated in megahertz shows a reading of 3.525 MHz, what would it show if it were calibrated in kilohertz?
A. 0.003525 kHz
B. 35.25 kHz
C. 3525 kHz
D. 3,525,000 kHz
~~
*T5B08
How many microfarads are 1,000,000 picofarads?
A. 0.001 microfarads
B. 1 microfarad
C. 1000 microfarads
D. 1,000,000,000 microfarads
~~
*T5B09
What is the approximate amount of change, measured in decibels (dB), of a power increase from 5 watts to 10 watts?
A. 2 dB
B. 3 dB
C. 5 dB
D. 10 dB
~~
*T5B10
What is the approximate amount of change, measured in decibels (dB), of a power decrease from 12 watts to 3 watts?
A. 1 dB
B. 3 dB
C. 6 dB
D. 9 dB
~~
*T5B11
What is the approximate amount of change, measured in decibels (dB), of a power increase from 20 watts to 200 watts?
A. 10 dB
B. 12 dB
C. 18 dB
D.28 dB
~~
Answers:
C, A, C, A, B, C, C, B, B, C, A
Lesson 1a
T5A - Electrical principles; current and voltage, conductors and insulators, alternating and direct current
(If you have not read the introduction please go back and read the introduction before you begin lesson 1.)
Before we start while learning about electronics I want to challenge each of you to try to dismiss from your thinking the relative terms big, little, large, small, fast, and slow. We may consider a race horse fast unless we compare it to a race car and that race car can not be considered fast when compared to the speed of a super sonic aircraft. As we study electricity and electronics if you try to compare speed, size, or numbers to the physical world you can see and touch it may hinder your ability to comprehend.
Some of these lessons use physical illustrations to help you understand but try not to get so wrapped up into the illustration that you get lost in the difference because I assure you the difference exceed the similarities.
You do not have to completely understand all of the physics behind the principles of electronics presented in these lessons to pass the technician class ham radio test. You can you can, and I hope you will, do a much deeper study and learn more as time goes by. For now you only have to understand enough to answer the questions on the test. I have tried to limit these lessons to just the information you need to pass the test.
As you start these studies think of an atom. Almost everyone today knows what an atom looks like even though we can not see them. It has a nucleus composed of protons and neutrons. Electrons orbit the nucleus.
The electrons have a negative charge and the protons have a positive charge. The term negative and positive do not have great significance beyond showing us that they are opposites.
Remember opposites attract and like repel. So electrons move away from other electrons while they move toward protons. Protons don’t move.
When an electron jumps out of its orbit it leaves that atom with more protons then electrons. That atom will then have a positive charge. Electricity is simply the movement of electrons. The medium through which electrons flow is usually a conductor.
The electrons in the atoms of copper, silver, aluminum, mercury, and other metals dislodge easily and thus make good conductors of electricity while the atoms in glass, wood, rubber, and many other things do not dislodge from their orbit easily thus they do not readily allow electrons to flow through them and are called insulators.
Electrons do not move through a conductor the same way as water flows through a pipe but the similarities will help explain some terms and help you remember them.
Flowing water has a current measured in gallons per minuets and electrons flowing through a conductor also have a current, an electrical current, which we measure in Amperes. Water pressure, measured in pounds per square inch, pushes the water to form the current while electrical pressure called Electromotive Force (EMF) or voltage pushes the electrons to form an electrical current. The basic unit of Electromotive Force is the volt.
The voltage and the amperage together determine the power consumed (the rate at which electrical energy is used) by an electrical circuit. The basic unit of electrical power is the watt. (Volts times Amperes equal Watts.)
When the electrons always move in the same direction the circuit is called Direct Current (DC). Remember electrons always move towards a more positive or less negative area so if the more positive area or terminal always remains in the same place the electrons will always flow in the same direction but if the positive terminal moves back and forth on the conductor the electrons will change their direction of flow. When the electrons change direction of flow on regular bases the resulting current flow is then called Alternating Current (AC).
Alternating current like direct current is measured in volts, amperes, and watts. AC has a rate of change called the frequency which needs to be measured. If the pendulum on a clock took one half second to swing from the center position or the very bottom of its swing to the highest position in one direction and come back to the center position and take another half second to swing through to its highest position on the other side of the swing and return to the center position before it starts its new upward movement that complete cycle of the pendulum and we could say the pendulum has a frequency of one cycle per second. Likewise if AC starts from its zero volt point and flows in one direction until it reaches its peak voltage then starts decreasing until it reaches zero volts again followed by a rise in voltage in the other direction to its peak then back down to zero it would have completed one cycle. AC frequency is measured in Hertz (Hz) so one complete cycle per second would equal one Hertz and sixty completed cycle in one second would equal sixty Hertz and so on.
The car battery is one common source of DC voltage with which most of us are familiar while the power source in household plugs is AC. To operate properly radios need a source of Direct Current at the proper operating voltage. Radios that plug directly into the household voltage have an internal circuit called the power supply that changes the AC voltage to proper DC voltage to supply power to the rest of the radio.
The auto industry settled on using 12 volts electrical systems in vehicles with internal combustion engines (the cars most of us drive today.) Most modern mobile transceiver (radio transmitter and receiver combined in one package) are designed to operate directly from the vehicles electrical system thus most mobile transceivers require 12 volts to operate propery. They can double as a base station simply by using a 120 VAC to 12 VDC power supply to supply the proper DC voltage, make sure the power supply has the necessary current capacity needed to transmit.
*T5A01
Electrical current is measured in which of the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes
~~
*T5A02
Electrical power is measured in which of the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes
~~
*T5A03
What is the name for the flow of electrons in an electric circuit?
A. Voltage
B. Resistance
C. Capacitance
D. Current
~~
*T5A04
What is the name for a current that flows only in one direction?
A. Alternating current
B. Direct current
C. Normal current
D. Smooth current
~
*T5A05
What is the electrical term for the electromotive force (EMF) that causes electron flow?
A. Voltage
B. Ampere-hours
C. Capacitance
D. Inductance
~~
*T5A06
How much voltage does a mobile transceiver usually require?
A. About 12 volts
B. About 30 volts
C. About 120 volts
D. About 240 volts
~~
*T5A07
Which of the following is a good electrical conductor?
A. Glass
B. Wood
C. Copper
D. Rubber
~~
*T5A08
Which of the following is a good electrical insulator?
A. Copper
B. Glass
C. Aluminum
D. Mercury
~~
*T5A09
What is the name for a current that reverses direction on a regular basis?
A. Alternating current
B. Direct current
C. Circular current
D. Vertical current
~~
*T5A10
Which term describes the rate at which electrical energy is used?
A. Resistance
B. Current
C. Power
D. Voltage
~~
*T5A11
What is the basic unit of electromotive force?
A. The volt
B. The watt
C. The ampere
D. The ohm
~~
Answers:
D, B, D, B, A, A, C, B, A, C, A
LESSON 1b
T5C - Electronic principles; capacitance, inductance, current flow in circuits, alternating current, definition of RF, power calculations T5D – Ohm’s Law
Water flowing through a pipe experiences opposition to flow do the resistance of the pipe. Electric current flowing through a conductor also experiences opposition to its flow do to electrical friction which is called resistance. The resistance of a circuit is measured in ohms.
If the EMF (voltage) remains constant and the resistance increases the current (number of amperes) will decrease. Likewise if the EMF decreases but the resistance remains constant the current will decrease. An increase in EMF or a decrease in resistance, while the other factor remains constant, will result in current increase.
The relationship between resistance, voltage, and current can be expressed mathematically in a formula we know as Ohm’s law. (Don’t panic it is not a scary as it might sound.) Just remember it takes one volt of electrical pressure to push one ampere of electrical current through one ohm of resistance. Increasing the pressure (EMF) will result in a current increase. If the resistance increases the current will decrease. If we divide the voltage by the resistance we get the current and if we divide the voltage by the current we get the resistance. If we know the current and the resistance we can find the voltage by multiplying the current times the resistance.
E (voltage) = I (current) X R (resistance) I=E/R R=E/I (When writing the formula I is used for intensity or current in amperes, E is used for EMF in volts, and R is used for resistance in ohms.)
So if a resistor has 3 amperes flowing through it and 90 volts across it the value of the resistor equals 90 divided by 3 (volts divided by amperes) which is 30 ohms. A 12 volt circuit with 1.5 amperes flowing has 8 ohms of resistance (12/1.5 = 8). A circuit with a 12 volt source which draws 4 amperes has a resistance of 3 ohms (12/4 = 3).
The current flowing through 80 ohms of resistance with an EMF of 120 volts (120 divided by 80) equals 1.5 amperes. The current flowing through a 100 ohm resistor connected across 200 volts is 2 amperes (200/100 = 2) and the current flowing through a 24 ohm resistor connected across 240 volts is 10 amperes (240/24 = 10).
Finally in our Ohm’s law calculations we need to know that the voltage across a 2 ohm resistor that has 0.5 amperes flowing through it is 1 volt because 2 times 0.5 is 1. The voltage across a 10 ohm resistor that will result in 1 ampere of current is 10 (10 X 1 = 10). A 10 ohm resistor with a current of 2 amperes flowing thought it is 20 volts (10 X 2 = 20).
The power produced by a circuit can be found by multiplying the voltage times the current. Thus a circuit with 13.8 volts DC applied with 10 amperes of current is using 138 watts of power (13.8 X 10 = 138). A circuit with 12 volts applied has 2.5 amperes of current will use 30 watts of power (12 X 2.5 = 30).
When the voltage and the power are the known quantities the current can be calculated by dividing the power by the voltage. Thus when a circuit is using 120 watts when 12 volts is applied the current equals 10 amperes (120/12 = 10).
Whether the circuit is AC or DC the electrical resistance will remain the same but Alternating Current can also have reactance which also oppose the flow of current. Reactance can be either inductive reactance or capacitive reactance. (At this point don’t worry about the term reactance for the test. I only bring it up to help you understand inductance and capacitance which are in the test questions for this lesson.)
Two conductors in close proximity of each other but separated by an insulator have an ability to form an electric field that can store an electrical charge. When the surface area of the conductor is increased or the insulator that separates the conductors is made thinner the amount of energy that can be stored is increased if the voltage remains constant. This ability to store energy in the form of an electric field is called capacitance. A basic unit of capacitance is the farad. The electronic component that utilizes this phenomenon to provide a given level of capacitance to a circuit is called a capacitor.
Electrical energy can also be stored in a magnetic field. When a wire conducts an electrical current it forms a magnetic field around it. A wire wrapped in a coil allows each turn in the coil to interact with the other turns and thus compress the magnetic field it forms in a small area and store energy. The ability to store energy in a magnetic field is called inductance thus the coil of wire used to provide a given amount of inductance can be referred to an inductor or a coil. Inductance is measured in henrys.
In lesson 1a alternating current was compared to the pendulum of a clock. When the pendulum is at its maximum point of swing in one direction it has to stop and start back in the other direction. The pendulum increases in speed as it falls (its kinetic energy increases) until it reaches bottom dead center (kinetic energy is maximum) then it starts to climb the other side and thus loose speed (kinetic energy decreases) until it stops (kinetic energy is zero) at its maximum point of swing and changes direction. The pendulum completes a cycle when it starts and moves to the opposite side and comes completely back to the starting position and moves through to the opposite side and comes back to its starting point.
I know this may seem redundant to what I said earlier but many people seem to have a difficulty in grasping frequency and I want everyone to understand. We can physically observe the frequency of a pendulum and hopefully that will help some grasp the principle of the movement of AC which we can not observe physically. The speed of movement of alternating current remains constant (near the speed of light) but the voltage and amperage rises and falls so the power (energy) will follow the rise and fall of the voltage and current (P=IE) so like the pendulum’s power changes throughout the cycle so does the AC power change through out its cycle. If you use zero volts or zero amperes as the beginning point of an AC cycle the current will then start to flow in a certain direction until it reaches a maximum (which will also be the maximum voltage and power) then the flow will decrease until it reaches zero then the current will start to flow in the other direction until it reaches maximum current flow and the current flow will then start to decrease until it reaches zero so it can change direction. That is one cycle. The number of cycles in a given second is called the frequency and is measured in hertz. So if there are 60 complete cycles in one second that circuit is said to be running at 60 Hertz (abbreviated as 60 Hz)
Alternating Current at high frequencies will create the electromagnetic waves that travel through space we know as radio waves. These radio waves or radio frequencies are frequently abbreviated as RF. All frequencies of radio waves can be referred to as RF.
*T5C01
What is the ability to store energy in an electric field called?
A. Inductance
B. Resistance
C. Tolerance
D. Capacitance
~~
*T5C02
What is the basic unit of capacitance?
A. The farad
B. The ohm
C. The volt
D. The henry
~~
*T5C03
What is the ability to store energy in a magnetic field called?
A. Admittance
B. Capacitance
C. Resistance
D. Inductance
~~
*T5C04
What is the basic unit of inductance?
A. The coulomb
B. The farad
C. The henry
D. The ohm
~~
*T5C05
What is the unit of frequency?
A. Hertz
B. Henry
C. Farad
D. Tesla
~~
*T5C06
What is the abbreviation that refers to radio frequency signals of all types?
A. AF
B. HF
C. RF
D. VHF
~~
*T5C07
What is a usual name for electromagnetic waves that travel through space?
A. Gravity waves
B. Sound waves
C. Radio waves
D. Pressure waves
~~
*T5C08
What is the formula used to calculate electrical power in a DC circuit?
A. Power (P) equals voltage (E) multiplied by current (I)
B. Power (P) equals voltage (E) divided by current (I)
C. Power (P) equals voltage (E) minus current (I)
D. Power (P) equals voltage (E) plus current (I)
~~
*T5C09
How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes?
A. 138 watts
B. 0.7 watts
C. 23.8 watts
D. 3.8 watts
~~
*T5C10
How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes?
A. 4.8 watts
B. 30 watts
C. 14.5 watts
D. 0.208 watts
~~
*T5C11
How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts?
A. 0.1 amperes
B. 10 amperes
C. 12 amperes
D. 132 amperes
~~
Answers: (T5C1 through T5C11)
D, A, D, C, A, C, C, A, A, B, B
*T5D01
What formula is used to calculate current in a circuit?
A. Current (I) equals voltage (E) multiplied by resistance (R)
B. Current (I) equals voltage (E) divided by resistance (R)
C. Current (I) equals voltage (E) added to resistance (R)
D. Current (I) equals voltage (E) minus resistance (R)
~~
*T5D02
What formula is used to calculate voltage in a circuit?
A. Voltage (E) equals current (I) multiplied by resistance (R)
B. Voltage (E) equals current (I) divided by resistance (R)
C. Voltage (E) equals current (I) added to resistance (R)
D. Voltage (E) equals current (I) minus resistance (R)
~~
*T5D03
What formula is used to calculate resistance in a circuit?
A. Resistance (R) equals voltage (E) multiplied by current (I)
B. Resistance (R) equals voltage (E) divided by current (I)
C. Resistance (R) equals voltage (E) added to current (I)
D. Resistance (R) equals voltage (E) minus current (I)
~~
*T5D04
What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts?
A. 3 ohms
B. 30 ohms
C. 93 ohms
D. 270 ohms
~~
*T5D05
What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
A. 18 ohms
B. 0.125 ohms
C. 8 ohms
D. 13.5 ohms
~~
*T5D06
What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
A. 3 ohms
B. 16 ohms
C. 48 ohms
D. 8 Ohms
~~
*T5D07
What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
A. 9600 amperes
B. 200 amperes
C. 0.667 amperes
D. 1.5 amperes
~~
*T5D08
What is the current flowing through a 100-ohm resistor connected across 200 volts?
A. 20,000 amperes
B. 0.5 amperes
C. 2 amperes
D. 100 amperes
~~
*T5D09
What is the current flowing through a 24-ohm resistor connected across 240 volts?
A. 24,000 amperes
B. 0.1 amperes
C. 10 amperes
D. 216 amperes
~~
*T5D10
What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
A. 1 volt
B. 0.25 volts
C. 2.5 volts
D. 1.5 volts
~~
*T5D11
What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
A. 1 volt
B. 10 volts
C. 11 volts
D. 9 volts
~~
*T5D12
What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
A. 8 volts
B. 0.2 volts
C. 12 volts
D. 20 volts
~~
Answers: (T5D1 through T5D12)
B, A, B, B, C, A, D, C, C, A, B, D
LESSON 1c
T5B - Math for electronics; decibels, electrical units and the metric system
Milli and micro are two prefixes commonly seen where the unit being named is less then a whole. Milli equals one thousandth (.001) 500 milliwatts equals 0.5 watts. Micro equals one millionth (.000,001) one microvolt is equal to one one-millionth of a volt. Sometimes whole numbers mixed with decimal numbers will use the milli prefix. An example of a whole number with a decimal number can be seen when writing 1.5 amperes which may also be listed as 1,500 milliamperes. .
If an ammeter (meter used to measure amperes) is calibrated in amperes is used to measure a circuit with 3000 milliamperes the reading would be 3 amperes.
Pico also frequently appears as a prefix but it is usually found in front of farads or the measure of capacitance. A picofarad is equal to one micro-micro-farad or one millionth of one millionth of one farad. Thus 1,000,000 picrofarads is equal to 1 microfarad.
Larger quantities also have prefixes to assist in expressing the quantity. Radio frequencies (remember radio waves are made by high frequency AC so they would be measured in Hertz) are usually listed as kilohertz (1,000 Hertz), megahertz (1,000,000 Hertz), and gigahertz (1,000,000,000 Hertz). They are abbreviated as KHz, MHz, and GHz respectively. Thus another way of expressing a radio signal frequency of 1,500,000 Hertz is 1500 KHz. A frequency readout calibrated in megahertz showing 3.525 MHz could be expressed as 3525 KHz.
A kilo just means one thousand so one kilovolt is equal to one thousand volts.
Mega means one million so one mega watt is equal to one million watts.
Decibels are not actual units they are comparative units. That is they are a way of comparing one power level to another. A full description of decibels can be very complicated and it is not necessary to pass the technician class amateur radio test.
Just try to remember if the power is doubled it is an increase of 3 decibels (abbreviated 3 dB) if the power is increased from 5 watts to 10 watts that is a 3 db change. If the power is decreased four times the changed expressed in decibels is 6 dB (if you have some experience in dB’s you may think what I just said is an error. It may seem like it should be -6 dB but that is not the way it is on the test and just accept that there is a 6 dB difference) so if 12 watts is decreased to 3 watts that is a 6 dB change. If the power difference is ten times then the change expressed in decibels is 10 dB so an increase of power from 20 watts to 200 watts is a 10 dB change.
If the power is doubled it is a 3 dB change.
If the power is decreased four times it is a 6 dB change.
If the power is increased ten times it is a 10 dB change.
That is all you need to know about decibels to pass the test. There are only three questions on decibels in the question pool only one of which might appear on your test.
*T5B01
How many milliamperes is 1.5 amperes?
A. 15 milliamperes
B. 150 milliamperes
C. 1,500 milliamperes
D. 15,000 milliamperes
~~
*T5B02
What is another way to specify a radio signal frequency of 1,500,000 hertz?
A. 1500 kHz
B. 1500 MHz
C. 15 GHz
D. 150 kHz
~~
*T5B03
How many volts are equal to one kilovolt?
A. One one-thousandth of a volt
B. One hundred volts
C. One thousand volts
D. One million volts
~~
*T5B04
How many volts are equal to one microvolt?
A. One one-millionth of a volt
B. One million volts
C. One thousand kilovolts
D. One one-thousandth of a volt
~~
*T5B05
Which of the following is equivalent to 500 milliwatts?
A. 0.02 watts
B. 0.5 watts
C. 5 watts
D. 50 watts
~~
*T5B06
If an ammeter calibrated in amperes is used to measure a 3000-milliampere current, what reading would it show?
A. 0.003 amperes
B. 0.3 amperes
C. 3 amperes
D. 3,000,000 amperes
~~
*T5B07
If a frequency readout calibrated in megahertz shows a reading of 3.525 MHz, what would it show if it were calibrated in kilohertz?
A. 0.003525 kHz
B. 35.25 kHz
C. 3525 kHz
D. 3,525,000 kHz
~~
*T5B08
How many microfarads are 1,000,000 picofarads?
A. 0.001 microfarads
B. 1 microfarad
C. 1000 microfarads
D. 1,000,000,000 microfarads
~~
*T5B09
What is the approximate amount of change, measured in decibels (dB), of a power increase from 5 watts to 10 watts?
A. 2 dB
B. 3 dB
C. 5 dB
D. 10 dB
~~
*T5B10
What is the approximate amount of change, measured in decibels (dB), of a power decrease from 12 watts to 3 watts?
A. 1 dB
B. 3 dB
C. 6 dB
D. 9 dB
~~
*T5B11
What is the approximate amount of change, measured in decibels (dB), of a power increase from 20 watts to 200 watts?
A. 10 dB
B. 12 dB
C. 18 dB
D.28 dB
~~
Answers:
C, A, C, A, B, C, C, B, B, C, A
LESSON 2
SUBELEMENT T6 – Electrical components, semiconductors, circuit diagrams, component functions – [4 Exam Groups - 4 Questions]
Lesson 2a
T6A - Electrical components; fixed and variable resistors, capacitors, and inductors; fuses, switches, batteries
If you look at the printed circuit board of a modern piece of electronic equipment you can usually see several small items or components soldered to the board. Each component serves a purpose. An inductor can frequently be spotted because it is usually composed of a coil of wire.
Lesson one described EMF, Current, and Resistance and explained their relationship to each other. The current supplied by a voltage source can be opposed and thus controlled by a component with a predetermined resistance value known as a resistor. A fixed resistor does not have a means to change its value but variable resistors also known as potentiometer allows an operator or technician to change its resistance. Potentiometers are often used to control volume.
Do not become confused here. Both resistance and reactance oppose the flow of current but reactance only affects AC circuits and not DC. Resistance opposes the flow of current in a DC circuit
Two conductors in close proximity of each other but separated by an insulator have an ability to form an electric field that can store an electrical charge. When the surface area of the conductor is increased or the insulator that separates the conductors is made thinner the amount of energy that can be stored is increased if the voltage remains constant. This ability to store energy in the form of an electric field is called capacitance. A basic unit of capacitance is the farad. The electronic component that utilizes this phenomenon to provide a given level of capacitance to a circuit is called a capacitor.
Electrical energy can also be stored in a magnetic field. When a wire conducts an electrical current it forms a magnetic field around it. A wire wrapped in a coil allows each turn in the coil to interact with the other turns and thus compress the magnetic field it forms in a small area and store energy. The ability to store energy in a magnetic field is called inductance thus the coil of wire used to provide a given amount of inductance can be referred to an inductor or a coil. Inductance is measured in henrys.
A switch is used to connect and disconnect electrical circuits.
A fuse is designed to be the weakest link in an electrical circuit so if the current becomes excessive the fuse will open the circuit. By opening up when the current becomes too high the fuse protects other circuit components from current overloads.
A power source is necessary to operate any electronic device which included a ham radio. Mobiles and hand held radios normally use batteries as a power source. There are basically two types of batteries; the secondary cell which means it is rechargeable and primary cells which are considered not rechargeable. Carbon-zinc batteries are the most common primary cell batteries. Nickel-cadmium cells are secondary cells and a fully charged Nickel-cadmium cell will normally have a voltage of 1.2 volts.
*T6A01
What electrical component is used to oppose the flow of current in a DC circuit?
A. Inductor
B. Resistor
C. Voltmeter
D. Transformer
~~
*T6A02
What type of component is often used as an adjustable volume control?
A. Fixed resistor
B. Power resistor
C. Potentiometer
D. Transformer
~~
*T6A03
What electrical parameter is controlled by a potentiometer?
A. Inductance
B. Resistance
C. Capacitance
D. Field strength
~~
*T6A04
What electrical component stores energy in an electric field?
A. Resistor
B. Capacitor
C. Inductor
D. Diode
~~
*T6A05
What type of electrical component consists of two or more conductive surfaces separated by an insulator?
A. Resistor
B. Potentiometer
C. Oscillator
D. Capacitor
~~
*T6A06
What type of electrical component stores energy in a magnetic field?
A. Resistor
B. Capacitor
C. Inductor
D. Diode
~~
*T6A07
What electrical component is usually composed of a coil of wire?
A. Switch
B. Capacitor
C. Diode
D. Inductor
~~
T6A08
What electrical component is used to connect or disconnect electrical circuits?
A. Zener Diode
B. Switch
C. Inductor
D. Variable resistor
~~
*T6A09
What electrical component is used to protect other circuit components from current overloads?
A. Fuse
B. Capacitor
C. Shield
D. Inductor
~~
T6A10
What is the nominal voltage of a fully charged nickel-cadmium cell?
A. 1.0 volts
B. 1.2 volts
C. 1.5 volts
D. 2.2 volts
~~
T6A11
Which battery type is not rechargeable?
A. Nickel-cadmium
B. Carbon-zinc
C. Lead-acid
D. Lithium-ion
~~
Answers:
B, C, B, B, D, C, D, B, A, B, B
Lesson 2B
T6B – Semiconductors; basic principles of diodes and transistors
When I got my ham radio license, 1960, the most common active device used in amplifiers was the vacuum tube. (The term “active device” means the electronic component that uses voltage or current at the input to control the current flow at the output.) Transistor radios were just starting to become popular. Today the most common electronic components capable of using a voltage or current signal to control current flow is the transistor.
Semiconductors with special preparations make up the heart of modern solid state technology. Up to this point I have discussed conductors and insulators thus you may think a semiconductor is something that lies in between these two. The best way I know to explain a semiconductor is to say it is a conductor under certain conditions and an insulator under other conditions. Any greater explanation of semiconductors and how they work goes beyond the scope of these lessons and not necessary for you to know to get your Technician class license.
For now just accept that transistors, solid state diodes, Light Emitting diodes and other solid state components, not named here because they are not part of the test, are composed of treated semiconductors. There are two basic types of transistors: the bipolar junction transistor which is made of three layers of semiconductor material and the Field Effect Transistor abbreviated “FET”. For the purpose of the test remember that the bipolar transistor has an emitter electrode and the FET has a gate electrode.
Transistors can be used as an electronic switch or amplifier. The transistor is the main solid state component used as an amplifier.
The Diode allows current to flow in only one direction. The two elements of the diode are the “Anode” and the “Cathode.” A stripe on the body of the diode usually identifies the cathode side.
The Light Emitting Diode, abbreviated “LED”, will produce light while conducting current.
The input of an amplifier receives a signal then the amplifier processes it so a larger signal appears at the output. The ability of a transistor to amplify a signal is called “Gain.”
*T6B01
What class of electronic components is capable of using a voltage or current signal to control current flow?
A. Capacitors
B. Inductors
C. Resistors
D. Transistors
~~
*T6B02
What electronic component allows current to flow in only one direction?
A. Resistor
B. Fuse
C. Diode
D. Driven Element
~~
*T6B03
Which of these components can be used as an electronic switch or amplifier?
A. Oscillator
B. Potentiometer
C. Transistor
D. Voltmeter
~~
*T6B04
Which of these components is made of three layers of semiconductor material?
A. Alternator
B. Bipolar junction transistor
C. Triode
D. Pentagrid converter
~~
*T6B05
Which of the following electronic components can amplify signals?
A. Transistor
B. Variable resistor
C. Electrolytic capacitor
D. Multi-cell battery
~~
*T6B06
How is a semiconductor diode’s cathode lead usually identified?
A. With the word "cathode"
B. With a stripe
C. With the letter "C"
D. All of these choices are correct
~~
*T6B07
What does the abbreviation "LED" stand for?
A. Low Emission Diode
B. Light Emitting Diode
C. Liquid Emission Detector
D. Long Echo Delay
~~
*T6B08
What does the abbreviation "FET" stand for?
A. Field Effect Transistor
B. Fast Electron Transistor
C. Free Electron Transition
D. Field Emission Thickness
~~
*T6B09
What are the names of the two electrodes of a diode?
A. Plus and minus
B. Source and drain
C. Anode and cathode
D. Gate and base
~~
*T6B10
Which semiconductor component has an emitter electrode?
A. Bipolar transistor
B. Field effect transistor
C. Silicon diode
D. Bridge rectifier
~~
*T6B11
Which semiconductor component has a gate electrode?
A. Bipolar transistor
B. Field effect transistor
C. Silicon diode
D. Bridge rectifier
~~
*T6B12
What is the term that describes a transistor's ability to amplify a signal?
A. Gain
B. Forward resistance
C. Forward voltage drop
D. On resistance
~~
Answers:
D, C, C, B, A, B, B, A, C, A, B, A
LESSON 2c
T6C - Circuit diagrams; schematic symbols
The Technician class amateur radio license test may include some schematic symbol identification. Schematic symbols are standardized representations of components in an electrical wiring diagram. A schematic diagram gives an accurate representation of the way components are interconnected in an electrical circuit. It has nothing to do with the physical appearance of the components, the physical location of the components in the unit, or the wire lengths of components.
You do not need to learn how to actually read the diagrams but just how to identify a few individual components shown in the diagram.
There are four different components in diagram T1 which you may be asked to identify. Component 1 depicts a Resistor while component 2 is a Transistor. Component 3 of diagram T1 is a lamp and component 4 is a Battery.
The function of a transistor is to control the current. Section D has a question that refers to T1 and if you remember that a transistor controls current and that component 2 on the T1 drawing is a transistor you should score on that question if you get it.
Just look at them and try to remember what they look like. It might help to draw the individual components and label them.
Questions about four components from T2 appear in this section of the test question pool. They are as follows: component 6 is a Capacitor, component 8 is a light emitting diode, Component 9 shows a Variable Resistor, and component 4 is a Transformer.
Component 3 of T2 is a single-pole single-throw switch but that question will not appear until the next section.
Notice the similarity between component 1 in the T1 diagram and component 9 in the T2 drawing. They are both resistors but the arrow shows in component 9 of T2 identifies that the resistance is changeable or variable which makes it a variable resistor or potentiometer.
Diagram T3 only has two components to learn, component 3, the variable inductor (notice the arrow again which designates it as variable or changeable) and component 4 the antenna. (For information only and not on the test: Component 2 is a variable capacitor.)
*T6C01 (C)
What is the name for standardized representations of components in an electrical wiring diagram?
A. Electrical depictions
B. Grey sketch
C. Schematic symbols
D. Component callouts
~~
*T6C02 (A)
What is component 1 in figure T1?
A. Resistor
B. Transistor
C. Battery
D. Connector
~~
*T6C03
What is component 2 in figure T1?
A. Resistor
B. Transistor
C. Indicator lamp
D. Connector
~~
*T6C04
What is component 3 in figure T1?
A. Resistor
B. Transistor
C. Lamp
D. Ground symbol
~~
*T6C05
What is component 4 in figure T1?
A. Resistor
B. Transistor
C. Battery
D. Ground symbol
~~
*T6C06
What is component 6 in figure T2?
A. Resistor
B. Capacitor
C. Regulator IC
D. Transistor
~~
*T6C07
What is component 8 in figure T2?
A. Resistor
B. Inductor
C. Regulator IC
D. Light emitting diode
~~
*T6C08
What is component 9 in figure T2?
A. Variable capacitor
B. Variable inductor
C. Variable resistor
D. Variable transformer
~~
*T6C09
What is component 4 in figure T2?
A. Variable inductor
B. Double-pole switch
C. Potentiometer
D. Transformer
~~
T6C10
What is component 3 in figure T3?
A. Connector
B. Meter
C. Variable capacitor
D. Variable inductor
~~
T6C11
What is component 4 in figure T3?
A. Antenna
B. Transmitter
C. Dummy load
D. Ground
~~
T6C12
What do the symbols on an electrical circuit schematic diagram represent?
A. Electrical components
B. Logic states
C. Digital codes
D. Traffic nodes
~~
T6C13
Which of the following is accurately represented in electrical circuit schematic diagrams?
A. Wire lengths
B. Physical appearance of components
C. The way components are interconnected
D. All of these choices are correct
~~
Answers:
C, A, B, C, C, B, D, C, D, D, A, A, C
LESSON 2d
T6D - Component functions
Each component in an electronic circuit serves a specific purpose.
To provide the appropriate voltage for modern radio equipment the 120 VAC standard household power must be reduced significantly. A transformer can be used to reduce the AC voltage. Next the AC must be changed to DC because radios do not work directly on AC. A Rectifier changes alternating current into varying direct current signal. That varying direct current signal must be smoothed out but there are no questions in this section about components used to do that so I will not explain.
A regulator is used to control the amount of voltage from a power supply.
Switches are necessary to turn circuits on and off or to change the function of a circuit. Some switches are operated manually as the Single-pole single-throw switch like the one schematically drawn in Figure T2 item 3. Some switches are controlled by an electromagnet these switches are called relays.
Visual display of operation in electronic devices may be as simple as a light or group of lights. The LED is commonly used for this type of visual indicator. Other times the visual display requires a movement or meter. A meter can be used to display signal strength on a numeric scale.
Tuned circuits are the means of separating out specific frequencies of radio waves. That is how a radio receiver can select one station while rejecting others. A capacitor is used together with an inductor to make a tuned circuit.
A ham shack usually has the radios, transmitters and receivers, inside while the antennas are outside on some type of support. When the antenna and the radio are separated they need some form of feed-line or conductor to tie them together. Coaxial cable is commonly used to carry RF signals between a radio and antenna.
The function of a transistor controls the flow current in an electronic circuit. One question in this section refers to figure T1 component 2 which, as you learned earlier, represents a transistor. So it follows that component 2 in figure T1 controls the current.
In the 1960’s Integrated circuits (IC) began to show up in the field of electronics. An Integrated circuit is a way to combine several semiconductors and other components into one package.
*T6D01
Which of the following devices or circuits changes an alternating current into a varying direct current signal?
A. Transformer
B. Rectifier
C. Amplifier
D. Reflector
~~
*T6D02
What best describes a relay?
A. A switch controlled by an electromagnet
B. A current controlled amplifier
C. An optical sensor
D. A pass transistor
~~
*T6D03
What type of switch is represented by item 3 in figure T2?
A. Single-pole single-throw
B. Single-pole double-throw
C. Double-pole single-throw
D. Double-pole double-throw
~~
*T6D04
Which of the following can be used to display signal strength on a numeric scale?
A. Potentiometer
B. Transistor
C. Meter
D. Relay
~~
*T6D05
What type of circuit controls the amount of voltage from a power supply?
A. Regulator
B. Oscillator
C. Filter
D. Phase inverter
~~
*T6D06
What component is commonly used to change 120V AC house current to a lower AC voltage for other uses?
A. Variable capacitor
B. Transformer
C. Transistor
D. Diode
~~
*T6D07
Which of the following is commonly used as a visual indicator?
A. LED
B. FET
C. Zener diode
D. Bipolar transistor
~~
*T6D08
Which of the following is used together with an inductor to make a tuned circuit?
A. Resistor
B. Zener diode
C. Potentiometer
D. Capacitor
~~
*T6D09
What is the name of a device that combines several semiconductors and other components into one package?
A. Transducer
B. Multi-pole relay
C. Integrated circuit
D. Transformer
~~
*T6D10
What is the function of component 2 in Figure T1?
A. Give off light when current flows through it
B. Supply electrical energy
C. Control the flow of current
D. Convert electrical energy into radio waves
~~
*T6D11
Which of the following is a common use of coaxial cable?
A. Carry dc power from a vehicle battery to a mobile radio
B. Carry RF signals between a radio and antenna
C. Secure masts, tubing, and other cylindrical objects on towers
D. Connect data signals from a TNC to a computer
~~
Answers:
B, A, A, C, A, B, A, D, C, C, B
Lesson 2a
T6A - Electrical components; fixed and variable resistors, capacitors, and inductors; fuses, switches, batteries
If you look at the printed circuit board of a modern piece of electronic equipment you can usually see several small items or components soldered to the board. Each component serves a purpose. An inductor can frequently be spotted because it is usually composed of a coil of wire.
Lesson one described EMF, Current, and Resistance and explained their relationship to each other. The current supplied by a voltage source can be opposed and thus controlled by a component with a predetermined resistance value known as a resistor. A fixed resistor does not have a means to change its value but variable resistors also known as potentiometer allows an operator or technician to change its resistance. Potentiometers are often used to control volume.
Do not become confused here. Both resistance and reactance oppose the flow of current but reactance only affects AC circuits and not DC. Resistance opposes the flow of current in a DC circuit
Two conductors in close proximity of each other but separated by an insulator have an ability to form an electric field that can store an electrical charge. When the surface area of the conductor is increased or the insulator that separates the conductors is made thinner the amount of energy that can be stored is increased if the voltage remains constant. This ability to store energy in the form of an electric field is called capacitance. A basic unit of capacitance is the farad. The electronic component that utilizes this phenomenon to provide a given level of capacitance to a circuit is called a capacitor.
Electrical energy can also be stored in a magnetic field. When a wire conducts an electrical current it forms a magnetic field around it. A wire wrapped in a coil allows each turn in the coil to interact with the other turns and thus compress the magnetic field it forms in a small area and store energy. The ability to store energy in a magnetic field is called inductance thus the coil of wire used to provide a given amount of inductance can be referred to an inductor or a coil. Inductance is measured in henrys.
A switch is used to connect and disconnect electrical circuits.
A fuse is designed to be the weakest link in an electrical circuit so if the current becomes excessive the fuse will open the circuit. By opening up when the current becomes too high the fuse protects other circuit components from current overloads.
A power source is necessary to operate any electronic device which included a ham radio. Mobiles and hand held radios normally use batteries as a power source. There are basically two types of batteries; the secondary cell which means it is rechargeable and primary cells which are considered not rechargeable. Carbon-zinc batteries are the most common primary cell batteries. Nickel-cadmium cells are secondary cells and a fully charged Nickel-cadmium cell will normally have a voltage of 1.2 volts.
*T6A01
What electrical component is used to oppose the flow of current in a DC circuit?
A. Inductor
B. Resistor
C. Voltmeter
D. Transformer
~~
*T6A02
What type of component is often used as an adjustable volume control?
A. Fixed resistor
B. Power resistor
C. Potentiometer
D. Transformer
~~
*T6A03
What electrical parameter is controlled by a potentiometer?
A. Inductance
B. Resistance
C. Capacitance
D. Field strength
~~
*T6A04
What electrical component stores energy in an electric field?
A. Resistor
B. Capacitor
C. Inductor
D. Diode
~~
*T6A05
What type of electrical component consists of two or more conductive surfaces separated by an insulator?
A. Resistor
B. Potentiometer
C. Oscillator
D. Capacitor
~~
*T6A06
What type of electrical component stores energy in a magnetic field?
A. Resistor
B. Capacitor
C. Inductor
D. Diode
~~
*T6A07
What electrical component is usually composed of a coil of wire?
A. Switch
B. Capacitor
C. Diode
D. Inductor
~~
T6A08
What electrical component is used to connect or disconnect electrical circuits?
A. Zener Diode
B. Switch
C. Inductor
D. Variable resistor
~~
*T6A09
What electrical component is used to protect other circuit components from current overloads?
A. Fuse
B. Capacitor
C. Shield
D. Inductor
~~
T6A10
What is the nominal voltage of a fully charged nickel-cadmium cell?
A. 1.0 volts
B. 1.2 volts
C. 1.5 volts
D. 2.2 volts
~~
T6A11
Which battery type is not rechargeable?
A. Nickel-cadmium
B. Carbon-zinc
C. Lead-acid
D. Lithium-ion
~~
Answers:
B, C, B, B, D, C, D, B, A, B, B
Lesson 2B
T6B – Semiconductors; basic principles of diodes and transistors
When I got my ham radio license, 1960, the most common active device used in amplifiers was the vacuum tube. (The term “active device” means the electronic component that uses voltage or current at the input to control the current flow at the output.) Transistor radios were just starting to become popular. Today the most common electronic components capable of using a voltage or current signal to control current flow is the transistor.
Semiconductors with special preparations make up the heart of modern solid state technology. Up to this point I have discussed conductors and insulators thus you may think a semiconductor is something that lies in between these two. The best way I know to explain a semiconductor is to say it is a conductor under certain conditions and an insulator under other conditions. Any greater explanation of semiconductors and how they work goes beyond the scope of these lessons and not necessary for you to know to get your Technician class license.
For now just accept that transistors, solid state diodes, Light Emitting diodes and other solid state components, not named here because they are not part of the test, are composed of treated semiconductors. There are two basic types of transistors: the bipolar junction transistor which is made of three layers of semiconductor material and the Field Effect Transistor abbreviated “FET”. For the purpose of the test remember that the bipolar transistor has an emitter electrode and the FET has a gate electrode.
Transistors can be used as an electronic switch or amplifier. The transistor is the main solid state component used as an amplifier.
The Diode allows current to flow in only one direction. The two elements of the diode are the “Anode” and the “Cathode.” A stripe on the body of the diode usually identifies the cathode side.
The Light Emitting Diode, abbreviated “LED”, will produce light while conducting current.
The input of an amplifier receives a signal then the amplifier processes it so a larger signal appears at the output. The ability of a transistor to amplify a signal is called “Gain.”
*T6B01
What class of electronic components is capable of using a voltage or current signal to control current flow?
A. Capacitors
B. Inductors
C. Resistors
D. Transistors
~~
*T6B02
What electronic component allows current to flow in only one direction?
A. Resistor
B. Fuse
C. Diode
D. Driven Element
~~
*T6B03
Which of these components can be used as an electronic switch or amplifier?
A. Oscillator
B. Potentiometer
C. Transistor
D. Voltmeter
~~
*T6B04
Which of these components is made of three layers of semiconductor material?
A. Alternator
B. Bipolar junction transistor
C. Triode
D. Pentagrid converter
~~
*T6B05
Which of the following electronic components can amplify signals?
A. Transistor
B. Variable resistor
C. Electrolytic capacitor
D. Multi-cell battery
~~
*T6B06
How is a semiconductor diode’s cathode lead usually identified?
A. With the word "cathode"
B. With a stripe
C. With the letter "C"
D. All of these choices are correct
~~
*T6B07
What does the abbreviation "LED" stand for?
A. Low Emission Diode
B. Light Emitting Diode
C. Liquid Emission Detector
D. Long Echo Delay
~~
*T6B08
What does the abbreviation "FET" stand for?
A. Field Effect Transistor
B. Fast Electron Transistor
C. Free Electron Transition
D. Field Emission Thickness
~~
*T6B09
What are the names of the two electrodes of a diode?
A. Plus and minus
B. Source and drain
C. Anode and cathode
D. Gate and base
~~
*T6B10
Which semiconductor component has an emitter electrode?
A. Bipolar transistor
B. Field effect transistor
C. Silicon diode
D. Bridge rectifier
~~
*T6B11
Which semiconductor component has a gate electrode?
A. Bipolar transistor
B. Field effect transistor
C. Silicon diode
D. Bridge rectifier
~~
*T6B12
What is the term that describes a transistor's ability to amplify a signal?
A. Gain
B. Forward resistance
C. Forward voltage drop
D. On resistance
~~
Answers:
D, C, C, B, A, B, B, A, C, A, B, A
LESSON 2c
T6C - Circuit diagrams; schematic symbols
The Technician class amateur radio license test may include some schematic symbol identification. Schematic symbols are standardized representations of components in an electrical wiring diagram. A schematic diagram gives an accurate representation of the way components are interconnected in an electrical circuit. It has nothing to do with the physical appearance of the components, the physical location of the components in the unit, or the wire lengths of components.
You do not need to learn how to actually read the diagrams but just how to identify a few individual components shown in the diagram.
There are four different components in diagram T1 which you may be asked to identify. Component 1 depicts a Resistor while component 2 is a Transistor. Component 3 of diagram T1 is a lamp and component 4 is a Battery.
The function of a transistor is to control the current. Section D has a question that refers to T1 and if you remember that a transistor controls current and that component 2 on the T1 drawing is a transistor you should score on that question if you get it.
Just look at them and try to remember what they look like. It might help to draw the individual components and label them.
Questions about four components from T2 appear in this section of the test question pool. They are as follows: component 6 is a Capacitor, component 8 is a light emitting diode, Component 9 shows a Variable Resistor, and component 4 is a Transformer.
Component 3 of T2 is a single-pole single-throw switch but that question will not appear until the next section.
Notice the similarity between component 1 in the T1 diagram and component 9 in the T2 drawing. They are both resistors but the arrow shows in component 9 of T2 identifies that the resistance is changeable or variable which makes it a variable resistor or potentiometer.
Diagram T3 only has two components to learn, component 3, the variable inductor (notice the arrow again which designates it as variable or changeable) and component 4 the antenna. (For information only and not on the test: Component 2 is a variable capacitor.)
*T6C01 (C)
What is the name for standardized representations of components in an electrical wiring diagram?
A. Electrical depictions
B. Grey sketch
C. Schematic symbols
D. Component callouts
~~
*T6C02 (A)
What is component 1 in figure T1?
A. Resistor
B. Transistor
C. Battery
D. Connector
~~
*T6C03
What is component 2 in figure T1?
A. Resistor
B. Transistor
C. Indicator lamp
D. Connector
~~
*T6C04
What is component 3 in figure T1?
A. Resistor
B. Transistor
C. Lamp
D. Ground symbol
~~
*T6C05
What is component 4 in figure T1?
A. Resistor
B. Transistor
C. Battery
D. Ground symbol
~~
*T6C06
What is component 6 in figure T2?
A. Resistor
B. Capacitor
C. Regulator IC
D. Transistor
~~
*T6C07
What is component 8 in figure T2?
A. Resistor
B. Inductor
C. Regulator IC
D. Light emitting diode
~~
*T6C08
What is component 9 in figure T2?
A. Variable capacitor
B. Variable inductor
C. Variable resistor
D. Variable transformer
~~
*T6C09
What is component 4 in figure T2?
A. Variable inductor
B. Double-pole switch
C. Potentiometer
D. Transformer
~~
T6C10
What is component 3 in figure T3?
A. Connector
B. Meter
C. Variable capacitor
D. Variable inductor
~~
T6C11
What is component 4 in figure T3?
A. Antenna
B. Transmitter
C. Dummy load
D. Ground
~~
T6C12
What do the symbols on an electrical circuit schematic diagram represent?
A. Electrical components
B. Logic states
C. Digital codes
D. Traffic nodes
~~
T6C13
Which of the following is accurately represented in electrical circuit schematic diagrams?
A. Wire lengths
B. Physical appearance of components
C. The way components are interconnected
D. All of these choices are correct
~~
Answers:
C, A, B, C, C, B, D, C, D, D, A, A, C
LESSON 2d
T6D - Component functions
Each component in an electronic circuit serves a specific purpose.
To provide the appropriate voltage for modern radio equipment the 120 VAC standard household power must be reduced significantly. A transformer can be used to reduce the AC voltage. Next the AC must be changed to DC because radios do not work directly on AC. A Rectifier changes alternating current into varying direct current signal. That varying direct current signal must be smoothed out but there are no questions in this section about components used to do that so I will not explain.
A regulator is used to control the amount of voltage from a power supply.
Switches are necessary to turn circuits on and off or to change the function of a circuit. Some switches are operated manually as the Single-pole single-throw switch like the one schematically drawn in Figure T2 item 3. Some switches are controlled by an electromagnet these switches are called relays.
Visual display of operation in electronic devices may be as simple as a light or group of lights. The LED is commonly used for this type of visual indicator. Other times the visual display requires a movement or meter. A meter can be used to display signal strength on a numeric scale.
Tuned circuits are the means of separating out specific frequencies of radio waves. That is how a radio receiver can select one station while rejecting others. A capacitor is used together with an inductor to make a tuned circuit.
A ham shack usually has the radios, transmitters and receivers, inside while the antennas are outside on some type of support. When the antenna and the radio are separated they need some form of feed-line or conductor to tie them together. Coaxial cable is commonly used to carry RF signals between a radio and antenna.
The function of a transistor controls the flow current in an electronic circuit. One question in this section refers to figure T1 component 2 which, as you learned earlier, represents a transistor. So it follows that component 2 in figure T1 controls the current.
In the 1960’s Integrated circuits (IC) began to show up in the field of electronics. An Integrated circuit is a way to combine several semiconductors and other components into one package.
*T6D01
Which of the following devices or circuits changes an alternating current into a varying direct current signal?
A. Transformer
B. Rectifier
C. Amplifier
D. Reflector
~~
*T6D02
What best describes a relay?
A. A switch controlled by an electromagnet
B. A current controlled amplifier
C. An optical sensor
D. A pass transistor
~~
*T6D03
What type of switch is represented by item 3 in figure T2?
A. Single-pole single-throw
B. Single-pole double-throw
C. Double-pole single-throw
D. Double-pole double-throw
~~
*T6D04
Which of the following can be used to display signal strength on a numeric scale?
A. Potentiometer
B. Transistor
C. Meter
D. Relay
~~
*T6D05
What type of circuit controls the amount of voltage from a power supply?
A. Regulator
B. Oscillator
C. Filter
D. Phase inverter
~~
*T6D06
What component is commonly used to change 120V AC house current to a lower AC voltage for other uses?
A. Variable capacitor
B. Transformer
C. Transistor
D. Diode
~~
*T6D07
Which of the following is commonly used as a visual indicator?
A. LED
B. FET
C. Zener diode
D. Bipolar transistor
~~
*T6D08
Which of the following is used together with an inductor to make a tuned circuit?
A. Resistor
B. Zener diode
C. Potentiometer
D. Capacitor
~~
*T6D09
What is the name of a device that combines several semiconductors and other components into one package?
A. Transducer
B. Multi-pole relay
C. Integrated circuit
D. Transformer
~~
*T6D10
What is the function of component 2 in Figure T1?
A. Give off light when current flows through it
B. Supply electrical energy
C. Control the flow of current
D. Convert electrical energy into radio waves
~~
*T6D11
Which of the following is a common use of coaxial cable?
A. Carry dc power from a vehicle battery to a mobile radio
B. Carry RF signals between a radio and antenna
C. Secure masts, tubing, and other cylindrical objects on towers
D. Connect data signals from a TNC to a computer
~~
Answers:
B, A, A, C, A, B, A, D, C, C, B
LESSON 3
SUBELEMENT T3 – Radio wave characteristics, radio and electromagnetic properties, propagation modes – [3 Exam Questions - 3 Groups]
Lesson 3a
T3B - Radio and electromagnetic wave properties; the electromagnetic spectrum, wavelength vs. frequency, velocity of electromagnetic waves
A radio wave consists of two components: Electric and Magnetic fields. Thus radio waves are a form of electromagnetic radiation. Radio waves travel through free space at about 300,000,000 meters per second the same as the speed of light.
Radio waves are formed by rapidly changing alternating current. The number of times per second that an alternating current reverses direction is called Frequency and is measured in Hertz. The distance a radio wave travels during one complete cycle is its wavelength.
The approximate wavelength of radio waves is often used to identify the different frequency bands. So 50 MHz to 54 MHz is called the 6 meter band and 144 MHz to 148 MHz is called the 2 meter band.
The wavelengths of radio waves are normally measured in meters and they can be calculated. The formula for calculating wavelength is: Wavelength in meters equals 300 divided by the frequency in megahertz. Notice 300 is a constant and the frequency varies. The frequency is divided into the 300 so the larger the number for frequency the smaller the number will be for the wave length. The wave length gets shorter as the frequency increases.
The terms High Frequency (HF) and Very High Frequency (VHF) were used when 100 MHz was difficult to obtain so it was considered Very High Frequency. We have continued to maintain the scale established many decades ago. HF frequencies are radio waves from 3 MHz to 30 MHz. VHF frequencies are 30 MHz to 300 MHz and UHF frequencies extend from 300 MHz to 3000 MHz. To help remember this just remember HF starts at 3 MHz and when you multiply times 10 it is at the breaking point of HF to VHF. Then again multiply by 10 and it is the pivot point between VHF and UHF.
*T3B01
What is the name for the distance a radio wave travels during one complete cycle?
A. Wave speed
B. Waveform
C. Wavelength
D. Wave spread
~~
*T3B02
What term describes the number of times per second that an alternating current reverses direction?
A. Pulse rate
B. Speed
C. Wavelength
D. Frequency
~~
*T3B03
What are the two components of a radio wave?
A. AC and DC
B. Voltage and current
C. Electric and magnetic fields
D. Ionizing and non-ionizing radiation
~~
*T3B04
How fast does a radio wave travel through free space?
A. At the speed of light
B. At the speed of sound
C. Its speed is inversely proportional to its wavelength
D. Its speed increases as the frequency increases
~~
*T3B05
How does the wavelength of a radio wave relate to its frequency?
A. The wavelength gets longer as the frequency increases
B. The wavelength gets shorter as the frequency increases
C. There is no relationship between wavelength and frequency
D. The wavelength depends on the bandwidth of the signal
~~
*T3B06
What is the formula for converting frequency to wavelength in meters?
A. Wavelength in meters equals frequency in hertz multiplied by 300
B. Wavelength in meters equals frequency in hertz divided by 300
C. Wavelength in meters equals frequency in megahertz divided by 300
D. Wavelength in meters equals 300 divided by frequency in megahertz
~~
*T3B07
What property of radio waves is often used to identify the different frequency bands?
A. The approximate wavelength
B. The magnetic intensity of waves
C. The time it takes for waves to travel one mile
D. The voltage standing wave ratio of waves
~~
*T3B08
What are the frequency limits of the VHF spectrum?
A. 30 to 300 kHz
B. 30 to 300 MHz
C. 300 to 3000 kHz
D. 300 to 3000 MHz
~~
*T3B09
What are the frequency limits of the UHF spectrum?
A. 30 to 300 kHz
B. 30 to 300 MHz
C. 300 to 3000 kHz
D. 300 to 3000 MHz
~~
*T3B10
What frequency range is referred to as HF?
A. 300 to 3000 MHz
B. 30 to 300 MHz
C. 3 to 30 MHz
D. 300 to 3000 kHz
~~
*T3B11
What is the approximate velocity of a radio wave as it travels through free space?
A. 3000 kilometers per second
B. 300,000,000 meters per second
C. 300,000 miles per hour
D. 186,000 miles per hour
~~
Answers:
C, D, C, A, B, D, A, B, D, C, B
LESSON 3b
T3A - Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF and UHF; fading, multipath; wavelength vs. penetration; antenna orientation
Radio signals are polarized. If a half wave antenna is parallel to the horizon the signal it radiates is horizontally polarized. If the antenna is perpendicular to the horizon it is vertically polarized. For maximum transfer of signals between a transmitter and receiver both antennas should have the same polarization. Most mobile stations antennas are vertically polarized thus most repeater have vertical polarization. For long–distance CW and SSB contacts on VHF and UHF bands where signal strengths might be weak horizontal polarization is most commonly used. If the transmitting antenna and receiving antenna do not have the same polarization when attempting line of sight communications on the VHF or UHF bands the signals could be significantly weaker then.
The ability of HF signals to bounce off the upper atmosphere allows hams to communicate around the world. The Ionosphere is the part of the atmosphere that enables the propagation of radio signals around the world. The radio waves, normally HF radio signals, strike the Ionosphere and are reflected back to earth then bounce back up and down. A common effect of “skip” reflection between the Earth and the Ionosphere is the polarization of the original signal is randomized. That is why antenna polarization is not normally as critical on HF operations as it is on VHF and UHF.
When operating VHF and above (The bands authorized for technician class amateur radio operators) signals are more easily reflected from surrounding objects than are lower frequencies. Random combining of signals arriving via different path lengths (called multi-path) can cause irregular fading of signals from distant stations during times of generally good reception. Multi-path can result in weak or distorted signal or both. If another operator reports that your station’s 2 meter signals were strong just a few moments ago, but now they are week or distorted try moving a few feet, as random reflections may cause multi-path distortion.
When using a directional antenna on VHF and above frequencies reflected signals can sometimes work to an advantage. Your station might be able to access a distant repeater if buildings or obstructions are blocking the direct line of site path by trying to find a path that reflects signals to the repeater.
UHF signals often are more effective from inside buildings then VHF signals because UHF has a shorter wavelength than VHF which allows them to more easily penetrate the building’s structure.
Mobile stations transmitting while in motion will sometimes be heard by the receiving station with a rapid fluttering sound. This phenomenon is commonly referred to as “Picket fencing.”
The ability of receiving stations to detect and correct errors in data transmissions is one of the reasons data communications is so popular. If the error rate is too large it can slow down the communications, When VHF or UHF data signals propagate over multiple the error rates are likely to increase.
*T3A01
What should you do if another operator reports that your station’s 2 meter signals were strong just a moment ago, but now they are weak or distorted?
A. Change the batteries in your radio to a different type
B. Turn on the CTCSS tone
C. Ask the other operator to adjust his squelch control
D. Try moving a few feet, as random reflections may be causing multi-path distortion
~~
*T3A02
Why are UHF signals often more effective from inside buildings than VHF signals?
A. VHF signals lose power faster over distance
B. The shorter wavelength allows them to more easily penetrate the structure of buildings
C. This is incorrect; VHF works better than UHF inside buildings
D. UHF antennas are more efficient than VHF antennas
~~
*T3A03
What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands?
A. Right-hand circular
B. Left-hand circular
C. Horizontal
D. Vertical
~~
*T3A04
What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?
A. The modulation sidebands might become inverted
B. Signals could be significantly weaker
C. Signals have an echo effect on voices
D. Nothing significant will happen
~~
*T3A05
When using a directional antenna, how might your station be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path?
A. Change from vertical to horizontal polarization
B. Try to find a path that reflects signals to the repeater
C. Try the long path
D. Increase the antenna SWR
~~
*T3A06
What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?
A. Flip-flopping
B. Picket fencing
C. Frequency shifting
D. Pulsing
~~
*T3A07
What type of wave carries radio signals between transmitting and receiving stations?
A. Electromagnetic
B. Electrostatic
C. Surface acoustic
D. Magnetostrictive
~~
*T3A08
What is the cause of irregular fading of signals from distant stations during times of generally good reception?
A. Absorption of signals by the "D" layer of the ionosphere
B. Absorption of signals by the "E" layer of the ionosphere
C. Random combining of signals arriving via different path lengths
D. Intermodulation distortion in the local receiver
~~
*T3A09
Which of the following is a common effect of "skip" reflections between the Earth and the ionosphere?
A. The sidebands become reversed at each reflection
B. The polarization of the original signal is randomized
C. The apparent frequency of the received signal is shifted by a random amount
D. Signals at frequencies above 30 MHz become stronger with each reflection
~~
*T3A10
What may occur if VHF or UHF data signals propagate over multiple paths?
A. Transmission rates can be increased by a factor equal to the number of separate paths observed
B. Transmission rates must be decreased by a factor equal to the number of separate paths observed
C. No significant changes will occur if the signals are transmitting using FM
D. Error rates are likely to increase
~~
*T3A11
Which part of the atmosphere enables the propagation of radio signals around the world?
A. The stratosphere
B. The troposphere
C. The ionosphere
D. The magnetosphere
~~
Answers:
D, B, C, B, B, B, A, C, B, D, C
Lesson 3c
T3C - Propagation modes; line of sight, sporadic E, meteor, aurora scatter, tropospheric ducting, F layer skip, radio horizon
The ionosphere reflects HF signals back to earth which allows communications well beyond the horizon but UHF signals are rarely heard from stations outside the transmitting stations local coverage area because UHF signals are usually not reflected by the ionosphere.
The ionosphere has been divided into various layers which are designated by letters of the alphabet. The E and the F layers are the most significant for radio propagation. UHF signals VHF signals will normally pass through the ionosphere but occasionally the E layer will become ionized to a much higher level than normal. This is called a Sporadic E layer and it is the propagation type which is most commonly associated with occasional strong over-the-horizon signals on 10, 6, and 2 meter bands.
Because the sun ionizes the ionosphere and the ionization is usually closely associated with the sun spots then the higher frequency long range communications usually occur during the daylight hours. Thus daylight hours provides the best long distance communications propagation on 10 meters.
Sight or light horizon and radio horizon do not occur at the same distance from the source of the signal or light. The radio horizon is the distance at which radio signals between two points are effectively blocked by the curvature of the Earth. VHF and UHF radio signals will usually travel a little farther than the visual line of sight distance between two stations because the Earth seems a little less curved to radio signals then it does to light.
There are other factors that affect the way radio waves travel from a transmitter to a receiver. Sometimes a signal can reach a receiver where it may not be expected to reach because of “knife-edge” propagation. “Knife-edge” propagation results from signals being partially refracted around solid objects exhibiting sharp edges.
The aurora (Northern or Southern lights) are sometimes able to reflect VHF. The characteristic of a VHF signal received via aroral reflection will exhibit a rapid fluctuation of strength of the signal and often the sound is distorted. It is a sound once you hear you won’t forget but until you hear an aroral reflection it is hard to explain.
Meteor showers also give opportunity to use VHF to talk to stations over the horizon. 6 Meters is usually the band best suited to communicating via meteor scatter.
The Troposphere is that layer of the atmosphere in which we live and breathe. It extends up to about 25,000 feet above sea level. This is the layer in which our weather is generated. VHF and UHF signals can be heard from over the horizon with ranges of approximately 300 miles on a regular basis do to “Tropospheric scatter” also known as “Troposperic ducting.” Tropospheric ducting is caused by temperature inversions in the atmosphere.
*T3C01
Why are "direct" (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?
A. They are too weak to go very far
B. FCC regulations prohibit them from going more than 50 miles
C. UHF signals are usually not reflected by the ionosphere
D. They collide with trees and shrubbery and fade out
~~
*T3C02
Which of the following might be happening when VHF signals are being received from long distances?
A. Signals are being reflected from outer space
B. Signals are arriving by sub-surface ducting
C. Signals are being reflected by lightning storms in your area
D. Signals are being refracted from a sporadic E layer
~~
*T3C03
What is a characteristic of VHF signals received via auroral reflection?
A. Signals from distances of 10,000 or more miles are common
B. The signals exhibit rapid fluctuations of strength and often sound distorted
C. These types of signals occur only during winter nighttime hours
D. These types of signals are generally strongest when your antenna is aimed to the south (for stations in the Northern Hemisphere)
~~
*T3C04
Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?
A. Backscatter
B. Sporadic E
C. D layer absorption
D. Gray-line propagation
~~
*T3C05
What is meant by the term "knife-edge" propagation?
A. Signals are reflected back toward the originating station at acute angles
B. Signals are sliced into several discrete beams and arrive via different paths
C. Signals are partially refracted around solid objects exhibiting sharp edges
D. Signals propagated close to the band edge exhibiting a sharp cutoff
~~
*T3C06
What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
A. Tropospheric scatter
B. D layer refraction
C. F2 layer refraction
D. Faraday rotation
~~
*T3C07
What band is best suited to communicating via meteor scatter?
A. 10 meters
B. 6 meters
C. 2 meters
D. 70 cm
~~
*T3C08
What causes "tropospheric ducting"?
A. Discharges of lightning during electrical storms
B. Sunspots and solar flares
C. Updrafts from hurricanes and tornadoes
D. Temperature inversions in the atmosphere
~~
*T3C09
What is generally the best time for long-distance 10 meter band propagation?
A. During daylight hours
B. During nighttime hours
C. When there are coronal mass ejections
D. Whenever the solar flux is low
~~
*T3C10
What is the radio horizon?
A. The distance at which radio signals between two points are effectively blocked by the curvature of the Earth
B. The distance from the ground to a horizontally mounted antenna
C. The farthest point you can see when standing at the base of your antenna tower
D. The shortest distance between two points on the Earth's surface
~~
*T3C11
Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?
A. Radio signals move somewhat faster than the speed of light
B. Radio waves are not blocked by dust particles
C. The Earth seems less curved to radio waves than to light
D. Radio waves are blocked by dust particles
~~
Answers:
C, D, B, B, C, A, B, D, A, A, C
Lesson 3a
T3B - Radio and electromagnetic wave properties; the electromagnetic spectrum, wavelength vs. frequency, velocity of electromagnetic waves
A radio wave consists of two components: Electric and Magnetic fields. Thus radio waves are a form of electromagnetic radiation. Radio waves travel through free space at about 300,000,000 meters per second the same as the speed of light.
Radio waves are formed by rapidly changing alternating current. The number of times per second that an alternating current reverses direction is called Frequency and is measured in Hertz. The distance a radio wave travels during one complete cycle is its wavelength.
The approximate wavelength of radio waves is often used to identify the different frequency bands. So 50 MHz to 54 MHz is called the 6 meter band and 144 MHz to 148 MHz is called the 2 meter band.
The wavelengths of radio waves are normally measured in meters and they can be calculated. The formula for calculating wavelength is: Wavelength in meters equals 300 divided by the frequency in megahertz. Notice 300 is a constant and the frequency varies. The frequency is divided into the 300 so the larger the number for frequency the smaller the number will be for the wave length. The wave length gets shorter as the frequency increases.
The terms High Frequency (HF) and Very High Frequency (VHF) were used when 100 MHz was difficult to obtain so it was considered Very High Frequency. We have continued to maintain the scale established many decades ago. HF frequencies are radio waves from 3 MHz to 30 MHz. VHF frequencies are 30 MHz to 300 MHz and UHF frequencies extend from 300 MHz to 3000 MHz. To help remember this just remember HF starts at 3 MHz and when you multiply times 10 it is at the breaking point of HF to VHF. Then again multiply by 10 and it is the pivot point between VHF and UHF.
*T3B01
What is the name for the distance a radio wave travels during one complete cycle?
A. Wave speed
B. Waveform
C. Wavelength
D. Wave spread
~~
*T3B02
What term describes the number of times per second that an alternating current reverses direction?
A. Pulse rate
B. Speed
C. Wavelength
D. Frequency
~~
*T3B03
What are the two components of a radio wave?
A. AC and DC
B. Voltage and current
C. Electric and magnetic fields
D. Ionizing and non-ionizing radiation
~~
*T3B04
How fast does a radio wave travel through free space?
A. At the speed of light
B. At the speed of sound
C. Its speed is inversely proportional to its wavelength
D. Its speed increases as the frequency increases
~~
*T3B05
How does the wavelength of a radio wave relate to its frequency?
A. The wavelength gets longer as the frequency increases
B. The wavelength gets shorter as the frequency increases
C. There is no relationship between wavelength and frequency
D. The wavelength depends on the bandwidth of the signal
~~
*T3B06
What is the formula for converting frequency to wavelength in meters?
A. Wavelength in meters equals frequency in hertz multiplied by 300
B. Wavelength in meters equals frequency in hertz divided by 300
C. Wavelength in meters equals frequency in megahertz divided by 300
D. Wavelength in meters equals 300 divided by frequency in megahertz
~~
*T3B07
What property of radio waves is often used to identify the different frequency bands?
A. The approximate wavelength
B. The magnetic intensity of waves
C. The time it takes for waves to travel one mile
D. The voltage standing wave ratio of waves
~~
*T3B08
What are the frequency limits of the VHF spectrum?
A. 30 to 300 kHz
B. 30 to 300 MHz
C. 300 to 3000 kHz
D. 300 to 3000 MHz
~~
*T3B09
What are the frequency limits of the UHF spectrum?
A. 30 to 300 kHz
B. 30 to 300 MHz
C. 300 to 3000 kHz
D. 300 to 3000 MHz
~~
*T3B10
What frequency range is referred to as HF?
A. 300 to 3000 MHz
B. 30 to 300 MHz
C. 3 to 30 MHz
D. 300 to 3000 kHz
~~
*T3B11
What is the approximate velocity of a radio wave as it travels through free space?
A. 3000 kilometers per second
B. 300,000,000 meters per second
C. 300,000 miles per hour
D. 186,000 miles per hour
~~
Answers:
C, D, C, A, B, D, A, B, D, C, B
LESSON 3b
T3A - Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF and UHF; fading, multipath; wavelength vs. penetration; antenna orientation
Radio signals are polarized. If a half wave antenna is parallel to the horizon the signal it radiates is horizontally polarized. If the antenna is perpendicular to the horizon it is vertically polarized. For maximum transfer of signals between a transmitter and receiver both antennas should have the same polarization. Most mobile stations antennas are vertically polarized thus most repeater have vertical polarization. For long–distance CW and SSB contacts on VHF and UHF bands where signal strengths might be weak horizontal polarization is most commonly used. If the transmitting antenna and receiving antenna do not have the same polarization when attempting line of sight communications on the VHF or UHF bands the signals could be significantly weaker then.
The ability of HF signals to bounce off the upper atmosphere allows hams to communicate around the world. The Ionosphere is the part of the atmosphere that enables the propagation of radio signals around the world. The radio waves, normally HF radio signals, strike the Ionosphere and are reflected back to earth then bounce back up and down. A common effect of “skip” reflection between the Earth and the Ionosphere is the polarization of the original signal is randomized. That is why antenna polarization is not normally as critical on HF operations as it is on VHF and UHF.
When operating VHF and above (The bands authorized for technician class amateur radio operators) signals are more easily reflected from surrounding objects than are lower frequencies. Random combining of signals arriving via different path lengths (called multi-path) can cause irregular fading of signals from distant stations during times of generally good reception. Multi-path can result in weak or distorted signal or both. If another operator reports that your station’s 2 meter signals were strong just a few moments ago, but now they are week or distorted try moving a few feet, as random reflections may cause multi-path distortion.
When using a directional antenna on VHF and above frequencies reflected signals can sometimes work to an advantage. Your station might be able to access a distant repeater if buildings or obstructions are blocking the direct line of site path by trying to find a path that reflects signals to the repeater.
UHF signals often are more effective from inside buildings then VHF signals because UHF has a shorter wavelength than VHF which allows them to more easily penetrate the building’s structure.
Mobile stations transmitting while in motion will sometimes be heard by the receiving station with a rapid fluttering sound. This phenomenon is commonly referred to as “Picket fencing.”
The ability of receiving stations to detect and correct errors in data transmissions is one of the reasons data communications is so popular. If the error rate is too large it can slow down the communications, When VHF or UHF data signals propagate over multiple the error rates are likely to increase.
*T3A01
What should you do if another operator reports that your station’s 2 meter signals were strong just a moment ago, but now they are weak or distorted?
A. Change the batteries in your radio to a different type
B. Turn on the CTCSS tone
C. Ask the other operator to adjust his squelch control
D. Try moving a few feet, as random reflections may be causing multi-path distortion
~~
*T3A02
Why are UHF signals often more effective from inside buildings than VHF signals?
A. VHF signals lose power faster over distance
B. The shorter wavelength allows them to more easily penetrate the structure of buildings
C. This is incorrect; VHF works better than UHF inside buildings
D. UHF antennas are more efficient than VHF antennas
~~
*T3A03
What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands?
A. Right-hand circular
B. Left-hand circular
C. Horizontal
D. Vertical
~~
*T3A04
What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?
A. The modulation sidebands might become inverted
B. Signals could be significantly weaker
C. Signals have an echo effect on voices
D. Nothing significant will happen
~~
*T3A05
When using a directional antenna, how might your station be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path?
A. Change from vertical to horizontal polarization
B. Try to find a path that reflects signals to the repeater
C. Try the long path
D. Increase the antenna SWR
~~
*T3A06
What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?
A. Flip-flopping
B. Picket fencing
C. Frequency shifting
D. Pulsing
~~
*T3A07
What type of wave carries radio signals between transmitting and receiving stations?
A. Electromagnetic
B. Electrostatic
C. Surface acoustic
D. Magnetostrictive
~~
*T3A08
What is the cause of irregular fading of signals from distant stations during times of generally good reception?
A. Absorption of signals by the "D" layer of the ionosphere
B. Absorption of signals by the "E" layer of the ionosphere
C. Random combining of signals arriving via different path lengths
D. Intermodulation distortion in the local receiver
~~
*T3A09
Which of the following is a common effect of "skip" reflections between the Earth and the ionosphere?
A. The sidebands become reversed at each reflection
B. The polarization of the original signal is randomized
C. The apparent frequency of the received signal is shifted by a random amount
D. Signals at frequencies above 30 MHz become stronger with each reflection
~~
*T3A10
What may occur if VHF or UHF data signals propagate over multiple paths?
A. Transmission rates can be increased by a factor equal to the number of separate paths observed
B. Transmission rates must be decreased by a factor equal to the number of separate paths observed
C. No significant changes will occur if the signals are transmitting using FM
D. Error rates are likely to increase
~~
*T3A11
Which part of the atmosphere enables the propagation of radio signals around the world?
A. The stratosphere
B. The troposphere
C. The ionosphere
D. The magnetosphere
~~
Answers:
D, B, C, B, B, B, A, C, B, D, C
Lesson 3c
T3C - Propagation modes; line of sight, sporadic E, meteor, aurora scatter, tropospheric ducting, F layer skip, radio horizon
The ionosphere reflects HF signals back to earth which allows communications well beyond the horizon but UHF signals are rarely heard from stations outside the transmitting stations local coverage area because UHF signals are usually not reflected by the ionosphere.
The ionosphere has been divided into various layers which are designated by letters of the alphabet. The E and the F layers are the most significant for radio propagation. UHF signals VHF signals will normally pass through the ionosphere but occasionally the E layer will become ionized to a much higher level than normal. This is called a Sporadic E layer and it is the propagation type which is most commonly associated with occasional strong over-the-horizon signals on 10, 6, and 2 meter bands.
Because the sun ionizes the ionosphere and the ionization is usually closely associated with the sun spots then the higher frequency long range communications usually occur during the daylight hours. Thus daylight hours provides the best long distance communications propagation on 10 meters.
Sight or light horizon and radio horizon do not occur at the same distance from the source of the signal or light. The radio horizon is the distance at which radio signals between two points are effectively blocked by the curvature of the Earth. VHF and UHF radio signals will usually travel a little farther than the visual line of sight distance between two stations because the Earth seems a little less curved to radio signals then it does to light.
There are other factors that affect the way radio waves travel from a transmitter to a receiver. Sometimes a signal can reach a receiver where it may not be expected to reach because of “knife-edge” propagation. “Knife-edge” propagation results from signals being partially refracted around solid objects exhibiting sharp edges.
The aurora (Northern or Southern lights) are sometimes able to reflect VHF. The characteristic of a VHF signal received via aroral reflection will exhibit a rapid fluctuation of strength of the signal and often the sound is distorted. It is a sound once you hear you won’t forget but until you hear an aroral reflection it is hard to explain.
Meteor showers also give opportunity to use VHF to talk to stations over the horizon. 6 Meters is usually the band best suited to communicating via meteor scatter.
The Troposphere is that layer of the atmosphere in which we live and breathe. It extends up to about 25,000 feet above sea level. This is the layer in which our weather is generated. VHF and UHF signals can be heard from over the horizon with ranges of approximately 300 miles on a regular basis do to “Tropospheric scatter” also known as “Troposperic ducting.” Tropospheric ducting is caused by temperature inversions in the atmosphere.
*T3C01
Why are "direct" (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?
A. They are too weak to go very far
B. FCC regulations prohibit them from going more than 50 miles
C. UHF signals are usually not reflected by the ionosphere
D. They collide with trees and shrubbery and fade out
~~
*T3C02
Which of the following might be happening when VHF signals are being received from long distances?
A. Signals are being reflected from outer space
B. Signals are arriving by sub-surface ducting
C. Signals are being reflected by lightning storms in your area
D. Signals are being refracted from a sporadic E layer
~~
*T3C03
What is a characteristic of VHF signals received via auroral reflection?
A. Signals from distances of 10,000 or more miles are common
B. The signals exhibit rapid fluctuations of strength and often sound distorted
C. These types of signals occur only during winter nighttime hours
D. These types of signals are generally strongest when your antenna is aimed to the south (for stations in the Northern Hemisphere)
~~
*T3C04
Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?
A. Backscatter
B. Sporadic E
C. D layer absorption
D. Gray-line propagation
~~
*T3C05
What is meant by the term "knife-edge" propagation?
A. Signals are reflected back toward the originating station at acute angles
B. Signals are sliced into several discrete beams and arrive via different paths
C. Signals are partially refracted around solid objects exhibiting sharp edges
D. Signals propagated close to the band edge exhibiting a sharp cutoff
~~
*T3C06
What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
A. Tropospheric scatter
B. D layer refraction
C. F2 layer refraction
D. Faraday rotation
~~
*T3C07
What band is best suited to communicating via meteor scatter?
A. 10 meters
B. 6 meters
C. 2 meters
D. 70 cm
~~
*T3C08
What causes "tropospheric ducting"?
A. Discharges of lightning during electrical storms
B. Sunspots and solar flares
C. Updrafts from hurricanes and tornadoes
D. Temperature inversions in the atmosphere
~~
*T3C09
What is generally the best time for long-distance 10 meter band propagation?
A. During daylight hours
B. During nighttime hours
C. When there are coronal mass ejections
D. Whenever the solar flux is low
~~
*T3C10
What is the radio horizon?
A. The distance at which radio signals between two points are effectively blocked by the curvature of the Earth
B. The distance from the ground to a horizontally mounted antenna
C. The farthest point you can see when standing at the base of your antenna tower
D. The shortest distance between two points on the Earth's surface
~~
*T3C11
Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?
A. Radio signals move somewhat faster than the speed of light
B. Radio waves are not blocked by dust particles
C. The Earth seems less curved to radio waves than to light
D. Radio waves are blocked by dust particles
~~
Answers:
C, D, B, B, C, A, B, D, A, A, C
LESSON 4
SUBELEMENT T9 – Antennas, feedlines - [2 Exam Questions - 2 Groups]
Lesson 4a
T9A – Antennas; vertical and horizontal, concept of gain, common portable and mobile antennas, relationships between antenna length and frequency
A bad antenna connected to the most expensive transceiver can result in very poor or no communications while a good antenna connected to an inexpensive transceiver under the same conditions may have excellent communications. The antenna is the part of the station which links the transmitting station to the receiving station.
The most basic antenna is the half wave antenna. For many decades the center fed dipole has been the most common wire antenna. The dipole antenna consists of two quarter wave long wires connected to an insulator and stretched out between two supports. The feed line of a dipole connects across the insulator in the center and runs down to connect to the antenna input of the radio.
Since the resonant frequency (the frequency at which it works best) of a dipole antenna is directly related to the wavelength of the radio signal then it should seem reasonable that if the wires were cut to shorter lengths it would raise the resonant frequency of the antenna. So to change a dipole antenna to make it resonant on a higher frequency you can shorten it.
Most simple dipole antennas are mounted so the conductor is parallel to the Earth’s surface. When the conductor is parallel to the ground the antenna is horizontally polarized. If the conductor is at a right angle or perpendicular to the Earth’s surface the antenna is vertically polarized. The electric field of a vertical antenna is perpendicular to the Earth’s surface while the magnetic field is parallel to the Earth’s surface.
Though stations can be worked off the end of a dipole the direction of the strongest radiation of a half-wave dipole antenna in free space is broadside to the antenna.
A half wave antenna for 6 meter is approximately 112 inches long. A quarter wave antenna for 146 MHz (2 meter band) is approximately 19 inches long.
A beam antenna is an antenna that concentrates signals in one direction. The quad, Yagi, and dish are three types of these directional or beam antennas. Think of the beam antenna like the beam of a flashlight. The flash light focuses the light into a beam so it will light up a smaller area with greater intensity then the same bulb would do if it was allowed to radiate equally in all directions.
The beam antenna is one example of a gain antenna. A gain antenna increases the signal strength in a specified direction when compared to a reference antenna.
Hand held radios frequently have a shortened flexible antenna affectionately referred to as a “rubber duck.” The disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers is it does not transmit or receive as effectively as a full-sized antenna. Many hams are tempted to use their handheld radios inside their cars using just the “rubber duck” antenna. Using the “rubber duck” antenna inside your car is not usually a good idea because signals can be significantly weaker inside the vehicle than when it is outside the vehicle. Thus it is best if using a handheld radio inside a vehicle to attach an external antenna, such as a magmount antenna, to the antenna port.
*T9A01
What is a beam antenna?
A. An antenna built from aluminum I-beams
B. An omnidirectional antenna invented by Clarence Beam
C. An antenna that concentrates signals in one direction
D. An antenna that reverses the phase of received signals
~~
*T9A02
Which of the following is true regarding vertical antennas?
A. The magnetic field is perpendicular to the Earth
B. The electric field is perpendicular to the Earth
C. The phase is inverted
D. The phase is reversed
~~
*T9A03
Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface?
A. A ground wave antenna
B. A horizontally polarized antenna
C. A rhombic antenna
D. A vertically polarized antenna
~~
*T9A04
What is a disadvantage of the "rubber duck" antenna supplied with most handheld radio transceivers?
A. It does not transmit or receive as effectively as a full-sized antenna
B. It transmits a circularly polarized signal
C. If the rubber end cap is lost it will unravel very quickly
D. All of these choices are correct
~~
*T9A05
How would you change a dipole antenna to make it resonant on a higher frequency?
A. Lengthen it
B. Insert coils in series with radiating wires
C. Shorten it
D. Add capacity hats to the ends of the radiating wires
~~
*T9A06
What type of antennas are the quad, Yagi, and dish?
A. Non-resonant antennas
B. Loop antennas
C. Directional antennas
D. Isotropic antennas
~~
*T9A07
What is a good reason not to use a "rubber duck" antenna inside your car?
A. Signals can be significantly weaker than when it is outside of the vehicle
B. It might cause your radio to overheat
C. The SWR might decrease, decreasing the signal strength
D. All of these choices are correct
~~
*T9A08
What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?
A. 112
B. 50
C. 19
D. 12
~~
*T9A09
What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna?
A. 6
B. 50
C. 112
D. 236
~~
*T9A10
In which direction is the radiation strongest from a half-wave dipole antenna in free space?
A. Equally in all directions
B. Off the ends of the antenna
C. Broadside to the antenna
D. In the direction of the feedline
~~
*T9A11
What is meant by the gain of an antenna?
A. The additional power that is added to the transmitter power
B. The additional power that is lost in the antenna when transmitting on a higher frequency
C. The increase in signal strength in a specified direction when compared to a reference antenna
D. The increase in impedance on receive or transmit compared to a reference antenna
~~
Answers:
C, B, B, A, C, C, A, C, C, C, C
Lesson 4b
T9B - Feedlines; types, losses vs. frequency, SWR concepts, matching weather protection, connectors
For proper RF transmission and reception a good antenna will continuously prove itself a key factor but any antenna, no matter how good it is, can not function well if the conductor between the radio and the antenna does not do its job. Feedline is a conductor used to connect the antenna to the transmitter or receiver.
The most common feedline used for amateur radio operations is the 50 ohm coaxial cable. Coaxial cable is a conductor or wire surrounded by an insulator which is covered with a conductor, usually braided copper wire, which is then insulated and protected from weathering by an outer coat. The reason coaxial cable is used more often then other feedlines for amateur radio antenna systems is because it is easy to use and requires few special installation considerations.
Two common types of coaxial feedline used by amateur radio operators is the smaller RG-58 and the larger RG-8. Both are 50 ohm but because RG-8 is larger thus it has less loss at a given frequency. Air-insulated hard line is not commonly used in the ham shack but when compared to 50-ohm flexible coax (RG-8 and RG-58) and 75-ohm flexible coax it has the lowest loss at VHF and UHF frequencies. (Multi-conductor unbalanced cable is not a recognized feedline.)
As the frequency of a radio signal passing through coaxial cable increases the signal loss will also increase. Signal loss in a coax line turns into heat.
Weathering can increase feedline signal loss and coax connectors do not seal well against water. Thus coax connectors exposed to the weather should be sealed against water intrusion to prevent an increase in feedline loss.
Standing Wave Ratio (SWR) is the ratio of signal going from the transmitter to the antenna as compared to the amount of signal that is reflected back down the coax from the antenna. To allow the efficient transfer of power and reduce losses it is important to have a low SWR in an antenna system that uses coaxial cable feedline. A high SWR indicates there is an impedance mismatch in the antenna system. An antenna tuner can be used to match the antenna system’s impedance to the transceiver’s output impedance.
If erratic changes in SWR reading are noticed the cause might be a loose connection to an antenna or a feedline.
The PL-259 (male connector) and the SO-239 (female connector) are frequently referred to as UHF connectors. That is an unfortunate term because they are not the best connector to use at UHF frequencies. The origin of the term UHF connector seems to have some debate but does not appear on technician class test so don’t concern yourself with it. Of the connecters mentioned in the test the “N” type of connecter is the most suitable for use with frequencies at 400 MHz and above. The PL-259 connectors are commonly used at HF frequencies.
*T9B01
Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?
A. To reduce television interference
B. To allow the efficient transfer of power and reduce losses
C. To prolong antenna life
D. All of these choices are correct
~~
*T9B02
What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?
A. 8 ohms
B. 50 ohms
C. 600 ohms
D. 12 ohms
~~
*T9B03
Why is coaxial cable used more often than any other feedline for amateur radio antenna systems?
A. It is easy to use and requires few special installation considerations
B. It has less loss than any other type of feedline
C. It can handle more power than any other type of feedline
D. It is less expensive than any other types of feedline
~~
*T9B04
What does an antenna tuner do?
A. It matches the antenna system impedance to the transceiver's output impedance
B. It helps a receiver automatically tune in weak stations
C. It allows an antenna to be used on both transmit and receive
D. It automatically selects the proper antenna for the frequency band being used
~~
*T9B05
What generally happens as the frequency of a signal passing through coaxial cable is increased?
A. The apparent SWR increases
B. The reflected power increases
C. The characteristic impedance increases
D. The loss increases
~~
*T9B06
Which of the following connectors is most suitable for frequencies above 400 MHz?
A. A UHF (PL-259/SO-239) connector
B. A Type N connector
C. An RS-213 connector
D. A DB-23 connector
~~
*T9B07
Which of the following is true of PL-259 type coax connectors?
A. They are good for UHF frequencies
B. They are water tight
C. The are commonly used at HF frequencies
D. They are a bayonet type connector
~~
*T9B08
Why should coax connectors exposed to the weather be sealed against water intrusion?
A. To prevent an increase in feedline loss
B. To prevent interference to telephones
C. To keep the jacket from becoming loose
D. All of these choices are correct
~~
*T9B09
What might cause erratic changes in SWR readings?
A. The transmitter is being modulated
B. A loose connection in an antenna or a feedline
C. The transmitter is being over-modulated
D. Interference from other stations is distorting your signal
~~
*T9B10
What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables?
A. There is no significant difference between the two types
B. RG-58 cable has less loss at a given frequency
C. RG-8 cable has less loss at a given frequency
D. RG-58 cable can handle higher power levels
~~
*T9B11
Which of the following types of feedline has the lowest loss at VHF and UHF?
A. 50-ohm flexible coax
B. Multi-conductor unbalanced cable
C. Air-insulated hard line
D. 75-ohm flexible coax
~~
Answers:
B, B, A, A, D, B, C, A, B, C, C,
Lesson 4c
T7C – Antenna measurements and troubleshooting; measuring SWR, dummy loads, feedline failure modes
In general terms the standing wave ratio (SWR) is a measure of how well a load is matched to a transmission line (feedline). If the antenna and the feedline have a perfect match the SWR meter will read 1 to 1. A 4:1 (4 to 1) reading on the SWR meter means there is an impedance mismatch.
A high SWR results in power loss in the feedline. Power loss in the feedline is converted to heat.
A high SWR not only results in power loss but it is also can cause damage to transmitters. Many modern solid-state transmitters have a protection circuit built in which will begin to reduce the transmitters output power when the SWR reaches 2 to 1 and will continue to limit the power more as the SWR goes higher.
Most amateur radio stations use SWR meters to check the SWR of an antenna system but a directional watt meter can also be used to check the SWR.
An antenna analyzer is an instrument which can be used to determine if an antenna is resonant at the desired operating frequency without radiating a potential interfering signal.
During these lessons the term impedance has been mentioned several times. For the purpose of the ham test a full understanding of impedance is not necessary but at least a little understanding may help remember the answers to some of the questions and help understand how to set up your station when you get your license.
Earlier we learned that resistance is the opposition to current flow in an electrical circuit. When working with alternating current reactance will also oppose the flow of current. There are two types of reactance, inductive reactance and capacitive reactance. Adding capacitive reactance can reduce inductive reactance and visa versa. If both reactances are the same they cancel each other out and you are left with pure resistance. The overall total opposition to the flow of alternating current is the impedance. Impedance, reactance, and resistance are all measured in ohms.
That was a very brief and simple explanation to a very long and complex subject.
When a transmitter is said to have a 50 ohm output then it will operate most efficiently when working into a load of 50 ohm impedance with no reactance (capacitive and inductive reactance are balanced.) A pure DC resistance 50 ohm load can be placed on the output of a transmitter and if the load is capable of dissipating all of the power the transmitters delivers to it then the transmitter can safely be operated with that load on it but it will not radiate an RF signal. All of the RF energy is changed to heat.
A pure resistance load placed on the output of a transmitter is known as a “dummy load”. The primary purpose of a dummy load is to prevent the radiation of signals when making tests on a transmitter.
Coax cable is said to have characteristic impedance. That just means it will work most efficiently when the load and the source are both equal to its characteristic impedance. The source can be a transmitter or a receiver and the load usually means the antenna.
The coax running from the ham shack to the antenna needs to be sealed at the point where connectors are subject to weathering. Moisture contamination is the most common cause for failure of coaxial cables.
The outer jacked of coaxial cable should be resistant to ultraviolet light because ultraviolet light can damage the jacket and allow water to enter the cable. Most coax designed for radio transmitter use are resistant to ultraviolet light.
Most hams will never have the opportunity to use “air core” coaxial cable but the question does appear in the question pool. A disadvantage of “air core” coaxial cable when compared to foam or solid dielectric types of coax is it requires special techniques to prevent water absorption.
*T7C01
What is the primary purpose of a dummy load?
A. To prevent the radiation of signals when making tests
B. To prevent over-modulation of your transmitter
C. To improve the radiation from your antenna
D. To improve the signal to noise ratio of your receiver
~~
*T7C02
Which of the following instruments can be used to determine if an antenna is resonant at the desired operating frequency?
A. A VTVM
B. An antenna analyzer
C. A "Q" meter
D. A frequency counter
~~
*T7C03
What, in general terms, is standing wave ratio (SWR)?
A. A measure of how well a load is matched to a transmission line
B. The ratio of high to low impedance in a feedline
C. The transmitter efficiency ratio
D. An indication of the quality of your station’s ground connection
~~
*T7C04
What reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline?
A. 2 to 1
B. 1 to 3
C. 1 to 1
D. 10 to 1
~~
*T7C05
What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?
A. 2 to 1
B. 1 to 2
C. 6 to 1
D. 10 to 1
~~
*T7C06
What does an SWR reading of 4:1 mean?
A. An antenna loss of 4 dB
B. A good impedance match
C. An antenna gain of 4
D. An impedance mismatch
~~
*T7C07
What happens to power lost in a feedline?
A. It increases the SWR
B. It comes back into your transmitter and could cause damage
C. It is converted into heat
D. It can cause distortion of your signal
~~
*T7C08
What instrument other than an SWR meter could you use to determine if a feedline and antenna are properly matched?
A. Voltmeter
B. Ohmmeter
C. Iambic pentameter
D. Directional wattmeter
~~
*T7C09
Which of the following is the most common cause for failure of coaxial cables?
A. Moisture contamination
B. Gamma rays
C. The velocity factor exceeds 1.0
D. Overloading
~~
*T7C10
Why should the outer jacket of coaxial cable be resistant to ultraviolet light?
A. Ultraviolet resistant jackets prevent harmonic radiation
B. Ultraviolet light can increase losses in the cable’s jacket
C. Ultraviolet and RF signals can mix together, causing interference
D. Ultraviolet light can damage the jacket and allow water to enter the cable
~~
*T7C11
What is a disadvantage of "air core" coaxial cable when compared to foam or solid dielectric types?
A. It has more loss per foot
B. It cannot be used for VHF or UHF antennas
C. It requires special techniques to prevent water absorption
D. It cannot be used at below freezing temperatures
~~
Answers:
A, B, A, C, A, D, C, D, A, D, C
Lesson 4a
T9A – Antennas; vertical and horizontal, concept of gain, common portable and mobile antennas, relationships between antenna length and frequency
A bad antenna connected to the most expensive transceiver can result in very poor or no communications while a good antenna connected to an inexpensive transceiver under the same conditions may have excellent communications. The antenna is the part of the station which links the transmitting station to the receiving station.
The most basic antenna is the half wave antenna. For many decades the center fed dipole has been the most common wire antenna. The dipole antenna consists of two quarter wave long wires connected to an insulator and stretched out between two supports. The feed line of a dipole connects across the insulator in the center and runs down to connect to the antenna input of the radio.
Since the resonant frequency (the frequency at which it works best) of a dipole antenna is directly related to the wavelength of the radio signal then it should seem reasonable that if the wires were cut to shorter lengths it would raise the resonant frequency of the antenna. So to change a dipole antenna to make it resonant on a higher frequency you can shorten it.
Most simple dipole antennas are mounted so the conductor is parallel to the Earth’s surface. When the conductor is parallel to the ground the antenna is horizontally polarized. If the conductor is at a right angle or perpendicular to the Earth’s surface the antenna is vertically polarized. The electric field of a vertical antenna is perpendicular to the Earth’s surface while the magnetic field is parallel to the Earth’s surface.
Though stations can be worked off the end of a dipole the direction of the strongest radiation of a half-wave dipole antenna in free space is broadside to the antenna.
A half wave antenna for 6 meter is approximately 112 inches long. A quarter wave antenna for 146 MHz (2 meter band) is approximately 19 inches long.
A beam antenna is an antenna that concentrates signals in one direction. The quad, Yagi, and dish are three types of these directional or beam antennas. Think of the beam antenna like the beam of a flashlight. The flash light focuses the light into a beam so it will light up a smaller area with greater intensity then the same bulb would do if it was allowed to radiate equally in all directions.
The beam antenna is one example of a gain antenna. A gain antenna increases the signal strength in a specified direction when compared to a reference antenna.
Hand held radios frequently have a shortened flexible antenna affectionately referred to as a “rubber duck.” The disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers is it does not transmit or receive as effectively as a full-sized antenna. Many hams are tempted to use their handheld radios inside their cars using just the “rubber duck” antenna. Using the “rubber duck” antenna inside your car is not usually a good idea because signals can be significantly weaker inside the vehicle than when it is outside the vehicle. Thus it is best if using a handheld radio inside a vehicle to attach an external antenna, such as a magmount antenna, to the antenna port.
*T9A01
What is a beam antenna?
A. An antenna built from aluminum I-beams
B. An omnidirectional antenna invented by Clarence Beam
C. An antenna that concentrates signals in one direction
D. An antenna that reverses the phase of received signals
~~
*T9A02
Which of the following is true regarding vertical antennas?
A. The magnetic field is perpendicular to the Earth
B. The electric field is perpendicular to the Earth
C. The phase is inverted
D. The phase is reversed
~~
*T9A03
Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface?
A. A ground wave antenna
B. A horizontally polarized antenna
C. A rhombic antenna
D. A vertically polarized antenna
~~
*T9A04
What is a disadvantage of the "rubber duck" antenna supplied with most handheld radio transceivers?
A. It does not transmit or receive as effectively as a full-sized antenna
B. It transmits a circularly polarized signal
C. If the rubber end cap is lost it will unravel very quickly
D. All of these choices are correct
~~
*T9A05
How would you change a dipole antenna to make it resonant on a higher frequency?
A. Lengthen it
B. Insert coils in series with radiating wires
C. Shorten it
D. Add capacity hats to the ends of the radiating wires
~~
*T9A06
What type of antennas are the quad, Yagi, and dish?
A. Non-resonant antennas
B. Loop antennas
C. Directional antennas
D. Isotropic antennas
~~
*T9A07
What is a good reason not to use a "rubber duck" antenna inside your car?
A. Signals can be significantly weaker than when it is outside of the vehicle
B. It might cause your radio to overheat
C. The SWR might decrease, decreasing the signal strength
D. All of these choices are correct
~~
*T9A08
What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?
A. 112
B. 50
C. 19
D. 12
~~
*T9A09
What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna?
A. 6
B. 50
C. 112
D. 236
~~
*T9A10
In which direction is the radiation strongest from a half-wave dipole antenna in free space?
A. Equally in all directions
B. Off the ends of the antenna
C. Broadside to the antenna
D. In the direction of the feedline
~~
*T9A11
What is meant by the gain of an antenna?
A. The additional power that is added to the transmitter power
B. The additional power that is lost in the antenna when transmitting on a higher frequency
C. The increase in signal strength in a specified direction when compared to a reference antenna
D. The increase in impedance on receive or transmit compared to a reference antenna
~~
Answers:
C, B, B, A, C, C, A, C, C, C, C
Lesson 4b
T9B - Feedlines; types, losses vs. frequency, SWR concepts, matching weather protection, connectors
For proper RF transmission and reception a good antenna will continuously prove itself a key factor but any antenna, no matter how good it is, can not function well if the conductor between the radio and the antenna does not do its job. Feedline is a conductor used to connect the antenna to the transmitter or receiver.
The most common feedline used for amateur radio operations is the 50 ohm coaxial cable. Coaxial cable is a conductor or wire surrounded by an insulator which is covered with a conductor, usually braided copper wire, which is then insulated and protected from weathering by an outer coat. The reason coaxial cable is used more often then other feedlines for amateur radio antenna systems is because it is easy to use and requires few special installation considerations.
Two common types of coaxial feedline used by amateur radio operators is the smaller RG-58 and the larger RG-8. Both are 50 ohm but because RG-8 is larger thus it has less loss at a given frequency. Air-insulated hard line is not commonly used in the ham shack but when compared to 50-ohm flexible coax (RG-8 and RG-58) and 75-ohm flexible coax it has the lowest loss at VHF and UHF frequencies. (Multi-conductor unbalanced cable is not a recognized feedline.)
As the frequency of a radio signal passing through coaxial cable increases the signal loss will also increase. Signal loss in a coax line turns into heat.
Weathering can increase feedline signal loss and coax connectors do not seal well against water. Thus coax connectors exposed to the weather should be sealed against water intrusion to prevent an increase in feedline loss.
Standing Wave Ratio (SWR) is the ratio of signal going from the transmitter to the antenna as compared to the amount of signal that is reflected back down the coax from the antenna. To allow the efficient transfer of power and reduce losses it is important to have a low SWR in an antenna system that uses coaxial cable feedline. A high SWR indicates there is an impedance mismatch in the antenna system. An antenna tuner can be used to match the antenna system’s impedance to the transceiver’s output impedance.
If erratic changes in SWR reading are noticed the cause might be a loose connection to an antenna or a feedline.
The PL-259 (male connector) and the SO-239 (female connector) are frequently referred to as UHF connectors. That is an unfortunate term because they are not the best connector to use at UHF frequencies. The origin of the term UHF connector seems to have some debate but does not appear on technician class test so don’t concern yourself with it. Of the connecters mentioned in the test the “N” type of connecter is the most suitable for use with frequencies at 400 MHz and above. The PL-259 connectors are commonly used at HF frequencies.
*T9B01
Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?
A. To reduce television interference
B. To allow the efficient transfer of power and reduce losses
C. To prolong antenna life
D. All of these choices are correct
~~
*T9B02
What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?
A. 8 ohms
B. 50 ohms
C. 600 ohms
D. 12 ohms
~~
*T9B03
Why is coaxial cable used more often than any other feedline for amateur radio antenna systems?
A. It is easy to use and requires few special installation considerations
B. It has less loss than any other type of feedline
C. It can handle more power than any other type of feedline
D. It is less expensive than any other types of feedline
~~
*T9B04
What does an antenna tuner do?
A. It matches the antenna system impedance to the transceiver's output impedance
B. It helps a receiver automatically tune in weak stations
C. It allows an antenna to be used on both transmit and receive
D. It automatically selects the proper antenna for the frequency band being used
~~
*T9B05
What generally happens as the frequency of a signal passing through coaxial cable is increased?
A. The apparent SWR increases
B. The reflected power increases
C. The characteristic impedance increases
D. The loss increases
~~
*T9B06
Which of the following connectors is most suitable for frequencies above 400 MHz?
A. A UHF (PL-259/SO-239) connector
B. A Type N connector
C. An RS-213 connector
D. A DB-23 connector
~~
*T9B07
Which of the following is true of PL-259 type coax connectors?
A. They are good for UHF frequencies
B. They are water tight
C. The are commonly used at HF frequencies
D. They are a bayonet type connector
~~
*T9B08
Why should coax connectors exposed to the weather be sealed against water intrusion?
A. To prevent an increase in feedline loss
B. To prevent interference to telephones
C. To keep the jacket from becoming loose
D. All of these choices are correct
~~
*T9B09
What might cause erratic changes in SWR readings?
A. The transmitter is being modulated
B. A loose connection in an antenna or a feedline
C. The transmitter is being over-modulated
D. Interference from other stations is distorting your signal
~~
*T9B10
What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables?
A. There is no significant difference between the two types
B. RG-58 cable has less loss at a given frequency
C. RG-8 cable has less loss at a given frequency
D. RG-58 cable can handle higher power levels
~~
*T9B11
Which of the following types of feedline has the lowest loss at VHF and UHF?
A. 50-ohm flexible coax
B. Multi-conductor unbalanced cable
C. Air-insulated hard line
D. 75-ohm flexible coax
~~
Answers:
B, B, A, A, D, B, C, A, B, C, C,
Lesson 4c
T7C – Antenna measurements and troubleshooting; measuring SWR, dummy loads, feedline failure modes
In general terms the standing wave ratio (SWR) is a measure of how well a load is matched to a transmission line (feedline). If the antenna and the feedline have a perfect match the SWR meter will read 1 to 1. A 4:1 (4 to 1) reading on the SWR meter means there is an impedance mismatch.
A high SWR results in power loss in the feedline. Power loss in the feedline is converted to heat.
A high SWR not only results in power loss but it is also can cause damage to transmitters. Many modern solid-state transmitters have a protection circuit built in which will begin to reduce the transmitters output power when the SWR reaches 2 to 1 and will continue to limit the power more as the SWR goes higher.
Most amateur radio stations use SWR meters to check the SWR of an antenna system but a directional watt meter can also be used to check the SWR.
An antenna analyzer is an instrument which can be used to determine if an antenna is resonant at the desired operating frequency without radiating a potential interfering signal.
During these lessons the term impedance has been mentioned several times. For the purpose of the ham test a full understanding of impedance is not necessary but at least a little understanding may help remember the answers to some of the questions and help understand how to set up your station when you get your license.
Earlier we learned that resistance is the opposition to current flow in an electrical circuit. When working with alternating current reactance will also oppose the flow of current. There are two types of reactance, inductive reactance and capacitive reactance. Adding capacitive reactance can reduce inductive reactance and visa versa. If both reactances are the same they cancel each other out and you are left with pure resistance. The overall total opposition to the flow of alternating current is the impedance. Impedance, reactance, and resistance are all measured in ohms.
That was a very brief and simple explanation to a very long and complex subject.
When a transmitter is said to have a 50 ohm output then it will operate most efficiently when working into a load of 50 ohm impedance with no reactance (capacitive and inductive reactance are balanced.) A pure DC resistance 50 ohm load can be placed on the output of a transmitter and if the load is capable of dissipating all of the power the transmitters delivers to it then the transmitter can safely be operated with that load on it but it will not radiate an RF signal. All of the RF energy is changed to heat.
A pure resistance load placed on the output of a transmitter is known as a “dummy load”. The primary purpose of a dummy load is to prevent the radiation of signals when making tests on a transmitter.
Coax cable is said to have characteristic impedance. That just means it will work most efficiently when the load and the source are both equal to its characteristic impedance. The source can be a transmitter or a receiver and the load usually means the antenna.
The coax running from the ham shack to the antenna needs to be sealed at the point where connectors are subject to weathering. Moisture contamination is the most common cause for failure of coaxial cables.
The outer jacked of coaxial cable should be resistant to ultraviolet light because ultraviolet light can damage the jacket and allow water to enter the cable. Most coax designed for radio transmitter use are resistant to ultraviolet light.
Most hams will never have the opportunity to use “air core” coaxial cable but the question does appear in the question pool. A disadvantage of “air core” coaxial cable when compared to foam or solid dielectric types of coax is it requires special techniques to prevent water absorption.
*T7C01
What is the primary purpose of a dummy load?
A. To prevent the radiation of signals when making tests
B. To prevent over-modulation of your transmitter
C. To improve the radiation from your antenna
D. To improve the signal to noise ratio of your receiver
~~
*T7C02
Which of the following instruments can be used to determine if an antenna is resonant at the desired operating frequency?
A. A VTVM
B. An antenna analyzer
C. A "Q" meter
D. A frequency counter
~~
*T7C03
What, in general terms, is standing wave ratio (SWR)?
A. A measure of how well a load is matched to a transmission line
B. The ratio of high to low impedance in a feedline
C. The transmitter efficiency ratio
D. An indication of the quality of your station’s ground connection
~~
*T7C04
What reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline?
A. 2 to 1
B. 1 to 3
C. 1 to 1
D. 10 to 1
~~
*T7C05
What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?
A. 2 to 1
B. 1 to 2
C. 6 to 1
D. 10 to 1
~~
*T7C06
What does an SWR reading of 4:1 mean?
A. An antenna loss of 4 dB
B. A good impedance match
C. An antenna gain of 4
D. An impedance mismatch
~~
*T7C07
What happens to power lost in a feedline?
A. It increases the SWR
B. It comes back into your transmitter and could cause damage
C. It is converted into heat
D. It can cause distortion of your signal
~~
*T7C08
What instrument other than an SWR meter could you use to determine if a feedline and antenna are properly matched?
A. Voltmeter
B. Ohmmeter
C. Iambic pentameter
D. Directional wattmeter
~~
*T7C09
Which of the following is the most common cause for failure of coaxial cables?
A. Moisture contamination
B. Gamma rays
C. The velocity factor exceeds 1.0
D. Overloading
~~
*T7C10
Why should the outer jacket of coaxial cable be resistant to ultraviolet light?
A. Ultraviolet resistant jackets prevent harmonic radiation
B. Ultraviolet light can increase losses in the cable’s jacket
C. Ultraviolet and RF signals can mix together, causing interference
D. Ultraviolet light can damage the jacket and allow water to enter the cable
~~
*T7C11
What is a disadvantage of "air core" coaxial cable when compared to foam or solid dielectric types?
A. It has more loss per foot
B. It cannot be used for VHF or UHF antennas
C. It requires special techniques to prevent water absorption
D. It cannot be used at below freezing temperatures
~~
Answers:
A, B, A, C, A, D, C, D, A, D, C
LESSON 5
SUBELEMENT T7 – Station equipment; common transmitter and receiver problems, antenna measurements and troubleshooting, basic repair and testing – [4 Exam Questions - 4 Groups]
Lesson 5a
T7A - Station radios; receivers, transmitters, transceivers
Figure T6 is a block diagram Single-conversion superhetrodyne receiver. It has a Beat Frequency Oscillator (BFO) which feeds block #1 the detector of the receiver (a detector is the stage that removes the intelligence from a radio signal.) A detector feed by a BFO which is mixed with the Intermediate Frequency (IF) makes it a product detector and the function of a product detector is to detect CW and SSB signals.
The Mixer of a superhetrodyne receiver mixes together the incoming RF signal and the local oscillator’s output to shift the incoming signal to an Intermediate Frequency. This allows the signal to be amplified by the fixed frequency IF amplifier which is much easier then having to tune each amplifier stage individually and allows the receiver to have a narrower bandwidth. Narrower band width means the receiver is able to discriminate between a desired signal and nearby undesired signals. This ability to discriminate is referred to as the selectivity of a receiver.
Figure T7 is also a superhetrodyne receiver. More specifically it is an FM superhetrodyne receiver. There are tip-offs by looking at it that it is an FM receiver but one of the test questions associated with this drawing ask if block 1 is a frequency discriminator what type of radio is it. A discriminator demodulates or removes the audio from an FM signal. So if block 1 is a frequency discriminator Figure T7 is an FM receiver.
A Transverter is a device that can change a low power transmitter/exciter frequency to another frequency band. For example a Transverter might change a 28 MHz SSB signal to 222 MHz SSB signal.
If Figure T5 represents a transceiver with block 1 being the transmitter portion and block 3 representing the receiver portion of the transceiver then block 2 would represent the Transmit-receive switch. A transmitter’s output can not be fed directly into the front end of a receiver so either the transmitter and receiver must use separate antennas or some means must be used to isolate the receiver from the transmitter’s output while transmitting. The receiver in most cases is shutoff during transmission. The Transmit-Receive (T/R) switch can accomplish both functions.
The modulator combines a speech signal and an RF carrier. The modulator puts the speech signal on the carrier in the transmitter and the detector removes the speech signal from the carrier in the receiver.
Figure T4 represents a simple CW transmitter. The Telegraph key should give it away. Every transmitter must have at least one oscillator to generate an RF signal which the driver and power amplifier can amplify and send to the antenna. Thus block 1 must represent an oscillator.
Remember when answering the questions on the technician class amateur radio test you must choose the best or the most correct answer of the four potential answers given. Question T7A09 asks which of the following devices is most useful for VHF weak-signal communications? A quarter-wave antenna is the minimum resonant antenna and has no gain while the omni-directional antenna can have some gain but it is still not the most useful for VHF weak-signal communications. The mobile VHF FM transceiver also does not fit the category. Thus the only answer left is B a Multi-mode VHF transceiver. Just accept it that is the answer.
Handheld transceivers are normally less then five watts. An RF power amplifier can be used to increase the output power to a higher level.
The ability of a receiver to hear signals is called its sensitivity. High sensitivity means the receiver can hear a very small signal. The ability of a receiver to receive low signals can be increased by installing an RF preamplifier between the antenna and the receiver.
*T7A01
What is the function of a product detector?
A. Detect phase modulated signals
B. Demodulate FM signals
C. Detect CW and SSB signals
D. Combine speech and RF signals
~~
*T7A02
What type of receiver is shown in Figure T6?
A. Direct conversion
B. Super-regenerative
C. Single-conversion superheterodyne
D. Dual-conversion superheterodyne
~~
*T7A03
What is the function of a mixer in a superheterodyne receiver?
A. To reject signals outside of the desired passband
B. To combine signals from several stations together
C. To shift the incoming signal to an intermediate frequency
D. To connect the receiver with an auxiliary device, such as a TNC
~~
*T7A04
What circuit is pictured in Figure T7, if block 1 is a frequency discriminator?
A. A double-conversion receiver
B. A regenerative receiver
C. A superheterodyne receiver
D. An FM receiver
~~
*T7A05
What is the function of block 1 if figure T4 is a simple CW transmitter?
A. Reactance modulator
B. Product detector
C. Low-pass filter
D. Oscillator
~~
*T7A06
What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal?
A. High-pass filter
B. Low-pass filter
C. Transverter
D. Phase converter
~~
*T7A07
If figure T5 represents a transceiver in which block 1 is the transmitter portion and block 3 is the receiver portion, what is the function of block 2?
A. A balanced modulator
B. A transmit-receive switch
C. A power amplifier
D. A high-pass filter
~~
*T7A08
Which of the following circuits combines a speech signal and an RF carrier?
A. Beat frequency oscillator
B. Discriminator
C. Modulator
D. Noise blanker
~~
*T7A09
Which of the following devices is most useful for VHF weak-signal communication?
A. A quarter-wave vertical antenna
B. A multi-mode VHF transceiver
C. An omni-directional antenna
D. A mobile VHF FM transceiver
~~
*T7A10
What device increases the low-power output from a handheld transceiver?
A. A voltage divider
B. An RF power amplifier
C. An impedance network
D. A voltage regulator
~~
*T7A11
Which of the following circuits demodulates FM signals?
A. Limiter
B. Discriminator
C. Product detector
D. Phase inverter
~~
*T7A12
Which term describes the ability of a receiver to discriminate between multiple signals?
A. Tuning rate
B. Sensitivity
C. Selectivity
D. Noise floor
~~
*T7A13
Where is an RF preamplifier installed?
A. Between the antenna and receiver
B. At the output of the transmitter's power amplifier
C. Between a transmitter and antenna tuner
D. At the receiver's audio output
~~
Answers:
C, C, C, D, D, C, B, C, B, B, B, C, A
Lesson 5b
T7B – Common transmitter and receiver problems; symptoms of overload and overdrive, distortion, interference, over and under modulation, RF feedback, off frequency signals; fading and noise; problems with digital communications interfaces
The term interference is used to refer to any annoyance caused by a radio transmitter or caused to a radio receiver. It might be an electric fence that causes a buzzing noise that can be heard on an amateur receiver or it might be a ham radio transmitter can be heard on a telephone. The term interference is not limited to transmitter’s output interfering with a receiver.
When an amateur radio transmitter interferes with a near by non-cordless telephone the telephone is inadvertently acting as a radio receiver. The first step to be taken with this type of interference is to install an RF filter at the phone.
When the interference is with a cordless phone, cell phone, or some other receiving device the problem may be caused by fundamental overload. Fundamental overload interference is caused by a very strong signal that overloads the receiving device.
Fundamental overload, harmonics, and spurious emissions are all potential causes of interference. Harmonics are radio signals that are multiples of the fundamental frequency (the frequency the transmitter should be sending.) Harmonics can be sent by a transmitter if it is not properly designed or properly tuned. Spurious emissions are RF signals that are not harmonics that are being generated by a transmitter when it is not properly tuned or it has an error in design.
If someone tells you that your station’s transmissions are interfering with their radio or TV reception you should make sure that your station is functioning properly and that it does not cause interference to your own television.
Some easy to install devices that may be useful in correcting a radio frequency interference problem are Snap-on ferrite chokes, Low-pass and High-pass filters, and Band-rejection and Band-pass filters.
Part 15 of the FCC rules and regulations allows for the use of unlicensed very low power transmitters on the AM and FM broadcast bands. If your neighbor’s “Part 15” device is causing harmful interference to your amateur station you should work with your neighbor to identify the offending device. Politely inform your neighbor about the rules that require him to stop using the device if it causes interference. You should also check your station and make sure it meets the standards of good amateur practice.
At the present time VHF and UHF ham radio FM stations are allowed 5 KHz deviation. That means your signal can move above and below the carrier frequency by a maximum of 5 KHz when it is being modulated. The stronger the modulating signal the greater the deviation. If you are told your FM handheld or mobile transceiver is over deviating you should talk farther away from the microphone.
Noise on your vehicle’s electrical system can sometimes be transmitted along with your speech audio. This type of problem will usually be noticed by another operator who will report hearing a variable high-pitched whine on the audio from your mobile transmitter.
A report that your audio signal through a repeater is distorted or unintelligible could mean your transmitter is slightly off frequency, your batteries may be running low, or you could be in a bad location.
RF feedback in a transmitter or transceiver can cause you to receive reports of garbled, distorted, or unintelligible transmissions.
Digital communications is gaining popularity on the ham bands. When speaking of digital communications the acronym “BER” means “Bit Error Rate.”
*T7B01
What can you do if you are told your FM handheld or mobile transceiver is over deviating?
A. Talk louder into the microphone
B. Let the transceiver cool off
C. Change to a higher power level
D. Talk farther away from the microphone
~~
*T7B02
What is meant by fundamental overload in reference to a receiver?
A. Too much voltage from the power supply
B. Too much current from the power supply
C. Interference caused by very strong signals
D. Interference caused by turning the volume up too high
~~
*T7B03
Which of the following may be a cause of radio frequency interference?
A. Fundamental overload
B. Harmonics
C. Spurious emissions
D. All of these choices are correct
~~
*T7B04
What is the most likely cause of interference to a non-cordless telephone from a nearby transmitter?
A. Harmonics from the transmitter
B. The telephone is inadvertently acting as a radio receiver
C. Poor station grounding
D. Improper transmitter adjustment
~~
*T7B05
What is a logical first step when attempting to cure a radio frequency interference problem in a nearby telephone?
A. Install a low-pass filter at the transmitter
B. Install a high-pass filter at the transmitter
C. Install an RF filter at the telephone
D. Improve station grounding
~~
*T7B06
What should you do first if someone tells you that your station’s transmissions are interfering with their radio or TV reception?
A. Make sure that your station is functioning properly and that it does not cause interference to your own television
B. Immediately turn off your transmitter and contact the nearest FCC office for assistance
C. Tell them that your license gives you the right to transmit and nothing can be done to reduce the interference
D. Continue operating normally because your equipment cannot possibly cause any interference
~~
*T7B07
Which of the following may be useful in correcting a radio frequency interference problem?
A. Snap-on ferrite chokes
B. Low-pass and high-pass filters
C. Band-reject and band-pass filters
D. All of these choices are correct
~~
*T7B08
What should you do if a "Part 15" device in your neighbor’s home is causing harmful interference to your amateur station?
A. Work with your neighbor to identify the offending device
B. Politely inform your neighbor about the rules that require him to stop using the device if it causes interference
C. Check your station and make sure it meets the standards of good amateur practice
D. All of these choices are correct
~~
*T7B09
What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter?
A. Your microphone is picking up noise from an open window
B. You have the volume on your receiver set too high
C. You need to adjust your squelch control
D. Noise on the vehicle’s electrical system is being transmitted along with your speech audio
~~
*T7B10
What might be the problem if you receive a report that your audio signal through the repeater is distorted or unintelligible?
A. Your transmitter may be slightly off frequency
B. Your batteries may be running low
C. You could be in a bad location
D. All of these choices are correct
~~
*T7B11
What is a symptom of RF feedback in a transmitter or transceiver?
A. Excessive SWR at the antenna connection
B. The transmitter will not stay on the desired frequency
C. Reports of garbled, distorted, or unintelligible transmissions
D. Frequent blowing of power supply fuses
~~
*T7B12
What does the acronym "BER" mean when applied to digital communications systems?
A. Baud Enhancement Recovery
B. Baud Error Removal
C. Bit Error Rate
D. Bit Exponent Resource
~~
Answers:
D, C, D, B, C, A, D, D, D, D, C, C
Lesson 5c
T7D – Basic repair and testing; soldering, use of a voltmeter, ammeter, and ohmmeter
One of the most popular instruments found in the ham shack is the multimeter. The multimeter includes a voltmeter to measure electrical potential or Electromotive force, an ammeter to measure electrical current, and an ohmmeter to measure resistance. Access to each of these different meters is usually by just turning a knob on a rotary switch.
Care must be taken when using the multimeter not to have it on the ohmmeter or on the ammeter when measuring voltage. Attempting to measure voltage when the meter is switched to measure either resistance or current can result in damaging the meter. When measuring a circuit with an ohmmeter you should be sure the circuit is not powered on and all large capacitors are drained.
Sometimes an ohmmeter will read a low resistance when first connected then as time passes the resistance will increase. When this happens it is usually an indication that a large capacitor is in the circuit.
When making measurements a volt meter is placed in parallel with the circuit being measured. Current measurements are taken by placing the ammeter in series with the circuit being measured.
A soldering iron is another instrument that might be considered for your ham shack. If you plan to do any soldering be sure to use a non-corrosive flux. Rosen core solder is the best to use for radio or electronic soldering.
A good solder connection should have a shinny silver appearance. If the surface of the connection is grainy and dull then it is exhibiting the characteristic appearance of what is known as a “cold” solder joint and while circuit may work immediately after the solder connection is made but it could be the source of problems later on down the road.
*T7D01
Which instrument would you use to measure electric potential or electromotive force?
A. An ammeter
B. A voltmeter
C. A wavemeter
D. An ohmmeter
~~
*T7D02
What is the correct way to connect a voltmeter to a circuit?
A. In series with the circuit
B. In parallel with the circuit
C. In quadrature with the circuit
D. In phase with the circuit
~~
*T7D03
How is an ammeter usually connected to a circuit?
A. In series with the circuit
B. In parallel with the circuit
C. In quadrature with the circuit
D. In phase with the circuit
~~
*T7D04
Which instrument is used to measure electric current?
A. An ohmmeter
B. A wavemeter
C. A voltmeter
D. An ammeter
~~
*T7D05
What instrument is used to measure resistance?
A. An oscilloscope
B. A spectrum analyzer
C. A noise bridge
D. An ohmmeter
~~
*T7D06
Which of the following might damage a multimeter?
A. Measuring a voltage too small for the chosen scale
B. Leaving the meter in the milliamps position overnight
C. Attempting to measure voltage when using the resistance setting
D. Not allowing it to warm up properly
~~
*T7D07
Which of the following measurements are commonly made using a multimeter?
A. SWR and RF power
B. Signal strength and noise
C. Impedance and reactance
D. Voltage and resistance
~~
*T7D08
Which of the following types of solder is best for radio and electronic use?
A. Acid-core solder
B. Silver solder
C. Rosin-core solder
D. Aluminum solder
~~
*T7D09
What is the characteristic appearance of a "cold" solder joint?
A. Dark black spots
B. A bright or shiny surface
C. A grainy or dull surface
D. A greenish tint
~~
*T7D10
What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time?
A. The ohmmeter is defective
B. The circuit contains a large capacitor
C. The circuit contains a large inductor
D. The circuit is a relaxation oscillator
~~
*T7D11
Which of the following precautions should be taken when measuring circuit resistance with an ohmmeter?
A. Ensure that the applied voltages are correct
B. Ensure that the circuit is not powered
C. Ensure that the circuit is grounded
D. Ensure that the circuit is operating at the correct frequency
~~
Answers:
B, B, A, D, D, C, D, C, C, B, B,
Lesson 5a
T7A - Station radios; receivers, transmitters, transceivers
Figure T6 is a block diagram Single-conversion superhetrodyne receiver. It has a Beat Frequency Oscillator (BFO) which feeds block #1 the detector of the receiver (a detector is the stage that removes the intelligence from a radio signal.) A detector feed by a BFO which is mixed with the Intermediate Frequency (IF) makes it a product detector and the function of a product detector is to detect CW and SSB signals.
The Mixer of a superhetrodyne receiver mixes together the incoming RF signal and the local oscillator’s output to shift the incoming signal to an Intermediate Frequency. This allows the signal to be amplified by the fixed frequency IF amplifier which is much easier then having to tune each amplifier stage individually and allows the receiver to have a narrower bandwidth. Narrower band width means the receiver is able to discriminate between a desired signal and nearby undesired signals. This ability to discriminate is referred to as the selectivity of a receiver.
Figure T7 is also a superhetrodyne receiver. More specifically it is an FM superhetrodyne receiver. There are tip-offs by looking at it that it is an FM receiver but one of the test questions associated with this drawing ask if block 1 is a frequency discriminator what type of radio is it. A discriminator demodulates or removes the audio from an FM signal. So if block 1 is a frequency discriminator Figure T7 is an FM receiver.
A Transverter is a device that can change a low power transmitter/exciter frequency to another frequency band. For example a Transverter might change a 28 MHz SSB signal to 222 MHz SSB signal.
If Figure T5 represents a transceiver with block 1 being the transmitter portion and block 3 representing the receiver portion of the transceiver then block 2 would represent the Transmit-receive switch. A transmitter’s output can not be fed directly into the front end of a receiver so either the transmitter and receiver must use separate antennas or some means must be used to isolate the receiver from the transmitter’s output while transmitting. The receiver in most cases is shutoff during transmission. The Transmit-Receive (T/R) switch can accomplish both functions.
The modulator combines a speech signal and an RF carrier. The modulator puts the speech signal on the carrier in the transmitter and the detector removes the speech signal from the carrier in the receiver.
Figure T4 represents a simple CW transmitter. The Telegraph key should give it away. Every transmitter must have at least one oscillator to generate an RF signal which the driver and power amplifier can amplify and send to the antenna. Thus block 1 must represent an oscillator.
Remember when answering the questions on the technician class amateur radio test you must choose the best or the most correct answer of the four potential answers given. Question T7A09 asks which of the following devices is most useful for VHF weak-signal communications? A quarter-wave antenna is the minimum resonant antenna and has no gain while the omni-directional antenna can have some gain but it is still not the most useful for VHF weak-signal communications. The mobile VHF FM transceiver also does not fit the category. Thus the only answer left is B a Multi-mode VHF transceiver. Just accept it that is the answer.
Handheld transceivers are normally less then five watts. An RF power amplifier can be used to increase the output power to a higher level.
The ability of a receiver to hear signals is called its sensitivity. High sensitivity means the receiver can hear a very small signal. The ability of a receiver to receive low signals can be increased by installing an RF preamplifier between the antenna and the receiver.
*T7A01
What is the function of a product detector?
A. Detect phase modulated signals
B. Demodulate FM signals
C. Detect CW and SSB signals
D. Combine speech and RF signals
~~
*T7A02
What type of receiver is shown in Figure T6?
A. Direct conversion
B. Super-regenerative
C. Single-conversion superheterodyne
D. Dual-conversion superheterodyne
~~
*T7A03
What is the function of a mixer in a superheterodyne receiver?
A. To reject signals outside of the desired passband
B. To combine signals from several stations together
C. To shift the incoming signal to an intermediate frequency
D. To connect the receiver with an auxiliary device, such as a TNC
~~
*T7A04
What circuit is pictured in Figure T7, if block 1 is a frequency discriminator?
A. A double-conversion receiver
B. A regenerative receiver
C. A superheterodyne receiver
D. An FM receiver
~~
*T7A05
What is the function of block 1 if figure T4 is a simple CW transmitter?
A. Reactance modulator
B. Product detector
C. Low-pass filter
D. Oscillator
~~
*T7A06
What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal?
A. High-pass filter
B. Low-pass filter
C. Transverter
D. Phase converter
~~
*T7A07
If figure T5 represents a transceiver in which block 1 is the transmitter portion and block 3 is the receiver portion, what is the function of block 2?
A. A balanced modulator
B. A transmit-receive switch
C. A power amplifier
D. A high-pass filter
~~
*T7A08
Which of the following circuits combines a speech signal and an RF carrier?
A. Beat frequency oscillator
B. Discriminator
C. Modulator
D. Noise blanker
~~
*T7A09
Which of the following devices is most useful for VHF weak-signal communication?
A. A quarter-wave vertical antenna
B. A multi-mode VHF transceiver
C. An omni-directional antenna
D. A mobile VHF FM transceiver
~~
*T7A10
What device increases the low-power output from a handheld transceiver?
A. A voltage divider
B. An RF power amplifier
C. An impedance network
D. A voltage regulator
~~
*T7A11
Which of the following circuits demodulates FM signals?
A. Limiter
B. Discriminator
C. Product detector
D. Phase inverter
~~
*T7A12
Which term describes the ability of a receiver to discriminate between multiple signals?
A. Tuning rate
B. Sensitivity
C. Selectivity
D. Noise floor
~~
*T7A13
Where is an RF preamplifier installed?
A. Between the antenna and receiver
B. At the output of the transmitter's power amplifier
C. Between a transmitter and antenna tuner
D. At the receiver's audio output
~~
Answers:
C, C, C, D, D, C, B, C, B, B, B, C, A
Lesson 5b
T7B – Common transmitter and receiver problems; symptoms of overload and overdrive, distortion, interference, over and under modulation, RF feedback, off frequency signals; fading and noise; problems with digital communications interfaces
The term interference is used to refer to any annoyance caused by a radio transmitter or caused to a radio receiver. It might be an electric fence that causes a buzzing noise that can be heard on an amateur receiver or it might be a ham radio transmitter can be heard on a telephone. The term interference is not limited to transmitter’s output interfering with a receiver.
When an amateur radio transmitter interferes with a near by non-cordless telephone the telephone is inadvertently acting as a radio receiver. The first step to be taken with this type of interference is to install an RF filter at the phone.
When the interference is with a cordless phone, cell phone, or some other receiving device the problem may be caused by fundamental overload. Fundamental overload interference is caused by a very strong signal that overloads the receiving device.
Fundamental overload, harmonics, and spurious emissions are all potential causes of interference. Harmonics are radio signals that are multiples of the fundamental frequency (the frequency the transmitter should be sending.) Harmonics can be sent by a transmitter if it is not properly designed or properly tuned. Spurious emissions are RF signals that are not harmonics that are being generated by a transmitter when it is not properly tuned or it has an error in design.
If someone tells you that your station’s transmissions are interfering with their radio or TV reception you should make sure that your station is functioning properly and that it does not cause interference to your own television.
Some easy to install devices that may be useful in correcting a radio frequency interference problem are Snap-on ferrite chokes, Low-pass and High-pass filters, and Band-rejection and Band-pass filters.
Part 15 of the FCC rules and regulations allows for the use of unlicensed very low power transmitters on the AM and FM broadcast bands. If your neighbor’s “Part 15” device is causing harmful interference to your amateur station you should work with your neighbor to identify the offending device. Politely inform your neighbor about the rules that require him to stop using the device if it causes interference. You should also check your station and make sure it meets the standards of good amateur practice.
At the present time VHF and UHF ham radio FM stations are allowed 5 KHz deviation. That means your signal can move above and below the carrier frequency by a maximum of 5 KHz when it is being modulated. The stronger the modulating signal the greater the deviation. If you are told your FM handheld or mobile transceiver is over deviating you should talk farther away from the microphone.
Noise on your vehicle’s electrical system can sometimes be transmitted along with your speech audio. This type of problem will usually be noticed by another operator who will report hearing a variable high-pitched whine on the audio from your mobile transmitter.
A report that your audio signal through a repeater is distorted or unintelligible could mean your transmitter is slightly off frequency, your batteries may be running low, or you could be in a bad location.
RF feedback in a transmitter or transceiver can cause you to receive reports of garbled, distorted, or unintelligible transmissions.
Digital communications is gaining popularity on the ham bands. When speaking of digital communications the acronym “BER” means “Bit Error Rate.”
*T7B01
What can you do if you are told your FM handheld or mobile transceiver is over deviating?
A. Talk louder into the microphone
B. Let the transceiver cool off
C. Change to a higher power level
D. Talk farther away from the microphone
~~
*T7B02
What is meant by fundamental overload in reference to a receiver?
A. Too much voltage from the power supply
B. Too much current from the power supply
C. Interference caused by very strong signals
D. Interference caused by turning the volume up too high
~~
*T7B03
Which of the following may be a cause of radio frequency interference?
A. Fundamental overload
B. Harmonics
C. Spurious emissions
D. All of these choices are correct
~~
*T7B04
What is the most likely cause of interference to a non-cordless telephone from a nearby transmitter?
A. Harmonics from the transmitter
B. The telephone is inadvertently acting as a radio receiver
C. Poor station grounding
D. Improper transmitter adjustment
~~
*T7B05
What is a logical first step when attempting to cure a radio frequency interference problem in a nearby telephone?
A. Install a low-pass filter at the transmitter
B. Install a high-pass filter at the transmitter
C. Install an RF filter at the telephone
D. Improve station grounding
~~
*T7B06
What should you do first if someone tells you that your station’s transmissions are interfering with their radio or TV reception?
A. Make sure that your station is functioning properly and that it does not cause interference to your own television
B. Immediately turn off your transmitter and contact the nearest FCC office for assistance
C. Tell them that your license gives you the right to transmit and nothing can be done to reduce the interference
D. Continue operating normally because your equipment cannot possibly cause any interference
~~
*T7B07
Which of the following may be useful in correcting a radio frequency interference problem?
A. Snap-on ferrite chokes
B. Low-pass and high-pass filters
C. Band-reject and band-pass filters
D. All of these choices are correct
~~
*T7B08
What should you do if a "Part 15" device in your neighbor’s home is causing harmful interference to your amateur station?
A. Work with your neighbor to identify the offending device
B. Politely inform your neighbor about the rules that require him to stop using the device if it causes interference
C. Check your station and make sure it meets the standards of good amateur practice
D. All of these choices are correct
~~
*T7B09
What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter?
A. Your microphone is picking up noise from an open window
B. You have the volume on your receiver set too high
C. You need to adjust your squelch control
D. Noise on the vehicle’s electrical system is being transmitted along with your speech audio
~~
*T7B10
What might be the problem if you receive a report that your audio signal through the repeater is distorted or unintelligible?
A. Your transmitter may be slightly off frequency
B. Your batteries may be running low
C. You could be in a bad location
D. All of these choices are correct
~~
*T7B11
What is a symptom of RF feedback in a transmitter or transceiver?
A. Excessive SWR at the antenna connection
B. The transmitter will not stay on the desired frequency
C. Reports of garbled, distorted, or unintelligible transmissions
D. Frequent blowing of power supply fuses
~~
*T7B12
What does the acronym "BER" mean when applied to digital communications systems?
A. Baud Enhancement Recovery
B. Baud Error Removal
C. Bit Error Rate
D. Bit Exponent Resource
~~
Answers:
D, C, D, B, C, A, D, D, D, D, C, C
Lesson 5c
T7D – Basic repair and testing; soldering, use of a voltmeter, ammeter, and ohmmeter
One of the most popular instruments found in the ham shack is the multimeter. The multimeter includes a voltmeter to measure electrical potential or Electromotive force, an ammeter to measure electrical current, and an ohmmeter to measure resistance. Access to each of these different meters is usually by just turning a knob on a rotary switch.
Care must be taken when using the multimeter not to have it on the ohmmeter or on the ammeter when measuring voltage. Attempting to measure voltage when the meter is switched to measure either resistance or current can result in damaging the meter. When measuring a circuit with an ohmmeter you should be sure the circuit is not powered on and all large capacitors are drained.
Sometimes an ohmmeter will read a low resistance when first connected then as time passes the resistance will increase. When this happens it is usually an indication that a large capacitor is in the circuit.
When making measurements a volt meter is placed in parallel with the circuit being measured. Current measurements are taken by placing the ammeter in series with the circuit being measured.
A soldering iron is another instrument that might be considered for your ham shack. If you plan to do any soldering be sure to use a non-corrosive flux. Rosen core solder is the best to use for radio or electronic soldering.
A good solder connection should have a shinny silver appearance. If the surface of the connection is grainy and dull then it is exhibiting the characteristic appearance of what is known as a “cold” solder joint and while circuit may work immediately after the solder connection is made but it could be the source of problems later on down the road.
*T7D01
Which instrument would you use to measure electric potential or electromotive force?
A. An ammeter
B. A voltmeter
C. A wavemeter
D. An ohmmeter
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*T7D02
What is the correct way to connect a voltmeter to a circuit?
A. In series with the circuit
B. In parallel with the circuit
C. In quadrature with the circuit
D. In phase with the circuit
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*T7D03
How is an ammeter usually connected to a circuit?
A. In series with the circuit
B. In parallel with the circuit
C. In quadrature with the circuit
D. In phase with the circuit
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*T7D04
Which instrument is used to measure electric current?
A. An ohmmeter
B. A wavemeter
C. A voltmeter
D. An ammeter
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*T7D05
What instrument is used to measure resistance?
A. An oscilloscope
B. A spectrum analyzer
C. A noise bridge
D. An ohmmeter
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*T7D06
Which of the following might damage a multimeter?
A. Measuring a voltage too small for the chosen scale
B. Leaving the meter in the milliamps position overnight
C. Attempting to measure voltage when using the resistance setting
D. Not allowing it to warm up properly
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*T7D07
Which of the following measurements are commonly made using a multimeter?
A. SWR and RF power
B. Signal strength and noise
C. Impedance and reactance
D. Voltage and resistance
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*T7D08
Which of the following types of solder is best for radio and electronic use?
A. Acid-core solder
B. Silver solder
C. Rosin-core solder
D. Aluminum solder
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*T7D09
What is the characteristic appearance of a "cold" solder joint?
A. Dark black spots
B. A bright or shiny surface
C. A grainy or dull surface
D. A greenish tint
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*T7D10
What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time?
A. The ohmmeter is defective
B. The circuit contains a large capacitor
C. The circuit contains a large inductor
D. The circuit is a relaxation oscillator
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*T7D11
Which of the following precautions should be taken when measuring circuit resistance with an ohmmeter?
A. Ensure that the applied voltages are correct
B. Ensure that the circuit is not powered
C. Ensure that the circuit is grounded
D. Ensure that the circuit is operating at the correct frequency
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Answers:
B, B, A, D, D, C, D, C, C, B, B,
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