So what do we mean by Digital Radio in the world of Amateur Radio? Well much the same as we mean when applied to Digital Television, Digital Camera, and Digital recording. The information sent or stored is in a digital format. As with most things in Nature, Radio waves are Analogue. That is their value or amplitude various gradually with time and not instantaneously.
We have all heard of noughts and ones when talking about digital things that have just two states “0” or “1”, on or off. Now the problem is how do we use an analogue radio wave to send digitally formatted information? Well that was first developed over 100 years ago because the technology did not exist to send an analogue voice signal over an analogue radio wave.
Yes, Morse code, known as CW, Continuous Wave, but it is not, it is a series of breaks in transmission of a defined time related to the time the transmission is present. The dots and dashes, or as we prefer in Amateur Radio di’s and dah’s or dit when at the end of a charter like: B dah-di-di-dit.
Once it became possible to modulate the radio wave to send speech using AM then SSB, and finally FM it was possible to send one frequency for a “1” and another for a “0”, Mark and Space. Also could change the phase of the transmitted wave instantaneously to signal a Mark or Space.
Modern digital signalling methods use a combination of frequency change and phase change to transmit the digital format over the radio wave, the Carrier Wave. Back to CW for the twenty first century?
Amateur Radio uses the digital mobile radio technology DMR developed for the commercial world of mobile radio communications. You can suffer from information overload searching cyber space for a basic explanation in simple terms how DMR networks operate.
But before we discuss networks, the basic digital mode point to point communications needs to be considered using DMR modulation. There are other methods of digital modulation but DMR is very common and most digital radios and handhelds support it.
If you have never programmed a FM handheld radio for mobile to mobile and mobile to repeater working then it is best you get familiar with this before you start using Digital Mode. Radios can be programmed from their keypads, if they have one, but this is very laborious and prone to error, so best to load the programming software onto your computer and connect the radio’s programming cable between it and the computer.
Next: Digital Simplex Channels