Shortwave radio as a hobby gives us so different ways to listen to the signals we find on the bands, apart from the many interesting voice signals there are numerous data transmissions to decode and read.
Thankfully there is a lot of software (much of it free) for us to use that we can download and start decoding signals in a very short time.
Decoding of data modes is achieved by taking the sound output from a receiver and plugging it into a computer where the software will decode it.
Common Data Modes
RTTY (Radio Teletype)
The only other data mode older than RTTY is that grandaddy of radio Morse Code but it is still a popular mode with ham radio operators even though there are more efficient data modes available and can be found widely used on the HF bands.
PSK31 is a more robust data mode than RTTY and has fast been adopted by ham operators as the standard mode of communication when transmitting text.
PSK modes provide good error correction and easier to separate from RF noise there is no shortage of freeware decoding programs for the mode to be found on the internet.
AMTOR is an outdated legacy mode and is not used very often due to being replaced by the more efficient modes with better error correction and signal processing but you may come across is occasionally on certain segments of the HF bands.
Going away from ham terrestrial transmissions and over to satellites is the WEFAX (Weather Facsimile) system, to receive these satellite transmissions you need more specialized radio equipment and a dish pointing at the geostationary satellite.
The images received are very much like the ones you will see on any television weather report.
SSTV (slow scan television) is a very interesting and enjoyable data mode, still color images are transmitted over a narrow band width. The system is very similar to the way that normal commercial television signals are broadcast but because of the reduced band width they are sent a great deal slower.
As with the other data modes here there is a huge amount of freeware software and information online if you are thinking of starting with SSTV.
For some examples of what can be done with the available free software head on over to our SSTV picture collection
And many more….
These are just a few of the data modes that you can find on the HF, VHF and UHF bands. Ham radio operators widely use data modes and you can usually find something to listen to any time of the day or night on one of the many ham bands.
Multimode software packages will usually cover most of the common used modes and although all will do a competent job some specialized programs excel when it comes to decoding a few related transmission types.
PSK transmission photo courtesy Wikipedia