Article:  Andy Collinson
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Radio Data Modes
Around 70% of the radio spectrum is used for data modes, so its not surprising to find the garbled tones of data when searching for a new station. Data is present in most places of the electromagnetic spectrum and there are many techniques used in modulating and encoding the data. There are many programs available on the internet available to download and decode some data modes. All you need is a radio, computer and for some programs, a simple interface. Here is an outline of some of the data modes available and also links to various places on the internet that are sources of excellent information for further reading.

CW
Continuous Wave or Morse has been around since the beginning of radio, still used today by some amateur radio enthusiasts, though not as popular as some of the other modes. One advantage is that if you learn Morse, you can decode by just listening, no computer needed.

RTTY
RTTY or Radio TeleTYpe is very popular and transmitted at various speeds by amateur and commercial stations. Sometimes it is possible to tune in a RTTY signal perfectly, but still get jibberish, this is when the signal is encrypted.

FAX
Radio fax is used by weather stations across the globe. Decoding a nice weather map can be quite rewarding.

NAVTEX
Also known as Sitor B and used by ships and coastal radio stations for shipping and navigation. The main Navtex channel is on medium wave at 518kHz, but this band is closing and being favoured by satellite links.

PACKET
There are various modes of packet radio about, and the data structure of packet radio is quite robust, even weak signals can be decoded using this method.

Decoding Programs
Here are some links to internet sites that specialize in the various methods of radio transmission described above:-


CW
PA3BWK's Ultimate CW Web Site
Alan Gale's Beacon and Utility Site

RTTY, Navtex and Other Modes
Radioraft This program requires an interface but decodes many modes automatically


FAX
JVCOMM This is a great shareware program and does not require an interface

Packet
PSK31 A versatile decoder which can even decode two transmissions simultaneously, no interface required.

Decoding Links
Signal surfer DX Club
GSSR German Signal Search Ring -in German, but has lots of useful frequencies.