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Scramblers
Scramblers are electronic devices which, hence
its name, scramble your voice over the air. Scramblers use voice inversion or
sophisticated digital encoding/decoding of your speech. This prevents other
radio operators using normal modes in standard form from being able to
understand you.
Scramblers can be installed inside the radio or can be connected in series with
the microphone or in place of the microphone.
Spread Spectrum
Spread spectrum could also be considered as a type of scrambling. Spread Spectrum is used mostly by the military because it has good security and ant jamming capabilities. It also incorporates psuedo-random coding into it so it's difficult to follow the signal around. Spread spectrum communication is more complicated than normal RF communication. Spread spectrum is far more secure than an encrypted RF signal could ever be.
Radio Teletype
Please note: RTTY is NOT permitted on CB RADIO
Radio Teletype (RTTY) is a mode for transmitting printed messages over the air. The data coming out of the teleprinter is converted into tones, one tone called the mark and the other tone called the space. The conversion is done by a modem, that operates on the same principle as a phone modem or packet radio TNC. It simply modulates / demodulates the signal. The tones are transmitted using FSK
The mark frequency is 2125Hz and the space is 2275Hz. RTTY is commonly transmitted at speeds of 45.5 bits per second. RTTY is either transmitted in Baud or ASCII code.
Roger beeps
What are Roger beeps?
Roger beeps aid in the operation on SSB particularly over HF (below 30MHz) radio communications. Due to the fact SSB has no carrier wave, you can't actually tell when the other station has stopped transmitting, however, with a 'roger beep' system the radio can actually generate a beep when the microphone is released. This beep is transmitted after you finish transmitting. This can help greatly during long distance communications when the other stations signal might be poor.
Some modern digitally controlled radio equipment have the option to have an automatic beep when the microphone is released.
Slow Scan TV
Please note: SSTV is NOT permitted on CB
RADIO
Slow Scan TV (SSTV) is a transmission method for sending images via the
airwaves. These image types could be GIF, JPG, BMP or similar depending on the
computer software used for the SSTV transmissions.
It works similar to Facsimile transmissions. Each colour has it's own frequency
in SSTV mode and the software simply codes the colour into an audible frequency
tone that can be interfaced into the microphone system of the radio. The
receiving end software simply decodes the frequency tone back into the colour.
In fact, an SSTV signal can be recorded onto an audiotape and then played back
and decoded. Any number of people can simulatenously decode a single SSTV
transmission, just like 1000's of people can listen to the same radio station at
the same time or watch the same television channel.
SSTV is a relatively fast method of transmission, each transmission burst of
SSTV lasts about 30 seconds irrespective of file size.
Trunking is a type
of radio system. It is largely controlled by microprocessors to perform it's
task. Each radio that is to be used on the network has to be programmed to be on
the correct network with all the other trunking stations, for a courier service
for instance. The frequency is NOT fixed however.
Once any one station on the network transmits the base unit allocates a
frequency to the mobile station and that frequency is used by all other stations
until everyone has finished talking. Once the base unit has stopped transmitting
that frequency is cleared. A trunking system works like a big repeater system
though. All communications are two-way, however you are talking through
the base station trunking system. You aren't talking directly to any other one
station. Trunking base stations are generally positioned on the tops of city
buildings for the best radio range.
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This Web page was last updated on Friday September 21, 2001
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