LESSON 18

Oops I was supose to do this lesson yesterday.

Station hookup – microphone, speaker, headphones, filters,
power source, connecting a computer


The most basic components of any amateur radio station is a receiver, a transmitter, and an antenna. The transmitter and receiver can each be on a separate antenna or there can be a means of switching them back and forth so the transmitter power is not fed into the receiver’s front end. Sometimes the transmitter and receiver are housed in the same package and called a transceiver.

The transmitter will then have a way to allow the operator to communicate. This may be a telegraph key, microphone, teletype keyboard, or TV camera. If the receiver is not being used for remote control it will have a speaker so the electrical signals can be converted to sound waves. If working in a noisy environment or when not wishing to disturb other people a set of headphones can be used in place of the speaker.

Normally the position of the microphone and the speaker is not critical in an amateur radio station because normally the receiver either off or muted while transmitting but is both the transmitter and the receiver are being operated at the same time and the mike and the speaker are too close to each other audio feedback can occur.

Another factor that needs to be considered is power. AC power can not be applied directly to the amplifying circuits thus if the unit is to run off the house hold power a power supply, either internal or external to the transmitter and receiver, must be considered. The power supply provides the units with DC at the proper voltage levels. The power supply voltage should be held at a constant level even during changing loads. This is done by the regulator circuitry. So a regulated power supply prevents voltage fluxions during operation.

There are many filter types used in the radio industry. The power supply has a filter which is used to smooth out the AC ripple that will result when rectifying the AC. There are high pass filter which will allow all frequencies above a certain frequency to pass. A band pass filter which allows only a certain band of frequencies to pass. A band notch filter which will all except a certain band of frequencies to pass, and a low pass filter. A low pass filter will allow only those below a certain frequency to pass.

So if a two meter transmitter is causing problems with a television set a band pass filter could be placed on the output of the transmitter so as to be sure no spurious (unwanted) signals are being radiated. A band notch filter could be placed on the TV set to filter out the two meter frequencies. If a HF transmitter is interfering with a TV set a low pass filter could be used on the transmitter output to protect against radiating any signals above a certain frequency (usually 30 MHz) and a high pass filter could be used on the TV receiver to allow only signals above a certain frequency (Usually 54 MHz) to pass.

Packet radio is similar to Radio Teletype. It requires the connection of a computer to the transmitter and the receiver and as such will eliminate the need of either a microphone on the transmitter or a speaker on the receiver. The computer being used for packet or any other data transmission uses a sound card to interface with the radio equipment.





T5A01
What does a microphone connect to in a basic amateur radio
station?
A. The receiver
B. The transmitter
C. The SWR Bridge
D. The Balun
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T5A02
Which piece of station equipment converts electrical signals to sound waves?
A. Frequency coordinator
B. Frequency discriminator
C. Speaker
D. Microphone
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T5A03
What is the term used to describe what happens when a microphone and speaker are too close to each other?
A. Excessive wind noise
B. Audio feedback
C. Inverted signal patterns
D. Poor electrical grounding
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T5A04
What could you use in place of a regular speaker to help you copy signals in a noisy area?
A. A video display
B. A low pass filter
C. A set of headphones
D. A boom microphone
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T5A05
What is a good reason for using a regulated power supply for communications equipment?
A. To protect equipment from voltage fluctuations
B. A regulated power supply has FCC approval
C. A fuse or circuit breaker regulates the power
D. Regulated supplies are less expensive
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T5A06
Where must a filter be installed to reduce spurious emissions?
A. At the transmitter
B. At the receiver
C. At the station power supply
D. At the microphone
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T5A07
What type of filter should be connected to a TV receiver as the first step in trying to prevent RF overload from a nearby 2-meter transmitter?
A. Low-pass filter
B. High-pass filter
C. Band pass filter
D. Notch filter
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T5A08
What is connected between the transceiver and computer terminal in a packet radio station?
A. Transmatch
B. Mixer
C. Terminal Node Controller
D. Antenna
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T5A09
Which of these items is not required for a packet radio station?
A. Antenna
B. Transceiver
C. Power source
D. Microphone
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T5A10
What can be used to connect a radio with a computer for data transmission?
A. Balun
B. Sound Card
C. Impedance matcher
D. Autopatch
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Answers to today's questions.

B C B C A A D C D B