Digital Mobile Radio Sounds Awful
Published at 21:16 on 10 April 2013
Somewhat obscure geeky things that other ham radio operators generally overlook tend to interest me.
It’s one reason I bought a 900 MHz transceiver at the Puyallup swap meet last month; it’s a band with almost no equipment built and marketed to ham radio operators. It took some searching to find something suitable (in this case, an HT marketed to business and government users which could be unlocked and programmed on that amateur radio band).
Probably for the same reason, DMR (Digital Mobile Radio, commonly known by its Motorola trademark MOTOTRBO) piqued my interest. Unlike 900 MHz (which is very quiet), there’s actually a smattering of operators using that mode on the 70cm band.
The downside is that the audio sounds positively awful (I’ve been listening to it on the net here). Think cheezy sci-fi voice effects from the 70s, sometimes so heavy that one must strain to hear what is being said.
Maybe it shouldn’t have come as a complete surprise. Unlike digital home entertainment audio, greater fidelity was never a goal for DMR. Instead, the goal was to cram as many channels into as little radio spectrum as possible.
If that’s your main goal, quality is going to suffer. There’s nothing particularly magic (or evil) about digital technology in this regard; one can use analog techniques to compress signal bandwidth, and those have a negative effect on audio quality as well.
I haven’t done much listening to it, but I’ve heard the “official” digital protocol for amateur radio in the VHF and UHF bands, D-Star, suffers similarly.
I think the chief upshot of this awful sound is that we cannot expect any such digital mode to last nearly as long as analog voice modes have lasted. As technology improves, ways will be found to make audio suffer less as it is compressed into a digital signal. It still won’t be high fidelity, mind you, but it won’t leave the listener straining to discern speech, either.
Because of present poor audio quality, the high likelihood of rapid obsolescence, and the significantly higher cost of digital over analog, digital voice is unlikely to be more than a bit player on the ham bands in the near future.
To that can be added adoption issues. A business licensee is a single organization; it can decide to go digital, make the investment in equipment, and issue all employees new radios. We amateur radio operators are individuals making individual choices; this creates a high path dependency in favor of the status quo.
Moreover, the commercial and public service bands are much more congested, so being able to cram in more signals is more important there. Even so, I wouldn’t expect present-day digital technologies to have comparable longevity to, say, analog FM.