
More Information

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 Radio Systems

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.

Collin's Home Page Colin's Amateur Radio Page Colin's Snooker Page Colin's Guest Book Contact Me About Me

This Web page was last updated on Friday September 21, 2001