LESSON 24

Non-voice communications - image communications, data, CW,
packet, PSK31, Morse code techniques, Q signals

In the beginning of radio communications was Morse code. Morse code was first established for wire communications but Marconi found a way to use it in a wireless mode. A message is sent by Morse code by sending a series of impulses which expressed as either on or off thus it is a form of digital communications.

As time passed voice was added to radio communications. First Amplitude Modulation (AM) was used to impose voice on the radio frequency signal then Frequency Modulation (FM) became another technique of adding information to the electromagnetic spectrum. There is another form of modulation called Phase Modulation (PM) which, as far as the technical knowledge for the technician class license is concerned, is just a form of FM. (If you shift the frequency you shift the phase and if you shift the phase you shift the frequency and if you don’t have the slightest idea what I am talking about don’t worry about it because you don’t need to understand yet.)

So for all practical purposes it could be said there are three forms of placing intelligence on a radio signal. They are digital, AM, and FM. Sometimes a transmission may be a combination of these. Television is one example because the voice is normally FM while the video is AM. Single Sideband is a form of Amplitude Modulation.

As computers became more common in our homes it was natural that this technology would be used by some hams in association with their amateur radio activities. Computers can communicate with each other using digital communicating codes and hams found that they could link their computers together on the ham radio. A system was developed where messages could be passed from one ham station to another in a manor similar to teletype but by using groups called packets which could be sent to the receiving station and then sent back to the transmitting station to assure accuracy. This system of digital communications became known as Packet Radio.

T6C01 (D)
Which of the following is an example of a digital communications method?
A. Single sideband voice
B. Amateur television
C. FM voice
D. Packet radio
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T6C02 (A)
What does the term APRS mean?
A. Automatic Position Reporting System
B. Associated Public Radio Station
C. Auto Planning Radio Set-up
D. Advanced Polar Radio System
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T6C03 (D)
What item is required along with your normal radio for sending automatic location reports?
A. A connection to the vehicle speedometer
B. A connection to a WWV receiver
C. A connection to a broadcast FM sub-carrier receiver
D. A global positioning system receiver
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T6C04 (C)
What type of transmission is indicated by the term NTSC?
A. A Normal Transmission mode in Static Circuit
B. A special mode for earth satellite uplink
C. A standard fast scan color television signal
D. A frame compression scheme for TV signal
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T6C05 (B)
What emission mode may be used by a Technician class operator in the 219 - 220 MHz frequency range?
A. Slow-scan television
B. Point-to-point digital message forwarding
C. FM voice
D. Fast-scan television
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T6C06 (B)
What does the abbreviation PSK mean?
A. Pulse Shift Keying
B. Phase Shift Keying
C. Packet Short Keying
D. Phased Slide Keying
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T6C07 (D)
What is PSK31?
A. A high-rate data transmission mode used to transmit files
B. A method of reducing noise interference to FM signals
C. A type of television signal
D. A low-rate data transmission mode that works well in noisy conditions
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T6C08 (C)
What sending speed is recommended when using Morse code?
A. Only speeds below five WPM
B. The highest speed your keyer will operate
C. Any speed at which you can reliably receive
D. The highest speed at which you can control the keyer
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T6C09 (D)
What is a practical reason for being able to copy CW when using repeaters?
A. To send and receive messages others cannot overhear
B. To conform with FCC licensing requirements
C. To decode packet radio transmissions
D. To recognize a repeater ID sent in Morse code
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T6C10 (A)
What is the "Q" signal used to indicate that you are receiving interference from other stations?
A. QRM
B. QRN
C. QTH
D. QSB
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T6C11 (B)
What is the "Q" signal used to indicate that you are changing frequency?
A. QRU
B. QSY
C. QSL
D. QRZ


Answers: D A D C B B D C D A B~~