Digital radios are not just for hotspots…
I don’t know about you, but by and large, my DMR (and for that matter, D-STAR and Fusion) radio spends most of the time tuned to my personal hotspot. That’s great and I have some enjoyable and interesting contacts with it. But it’s been bugging me recently that we ought to get a lot more out of our digital radios than perhaps we do.
When I was chatting to Dave 5B4AOB the other day, he was telling me that VHF simplex activity on Cyprus is predominantly digital, which interested me. Then I saw a fascinating video of a simplex DMR contact over many hundreds of kilometres from the Med.
There’s one huge advantage of digital over analogue, of course. Whilst you’ve got an adequate signal, which might be a low level, but steady, you’ll have perfect audio. Take for example where I sit in the lounge of our house. The local Swindon repeaters are about 12-15 miles away over a typical path. On FM, the repeaters are quite easily audible, but there’s a fair bit of noise when you listen in the house on a handheld antenna. On DMR though, the signal is perfect (as long as you sit in the right place) with no hint of artefacts or breakup, unless an aircraft comes across and causes some multipath reflections. Until recently, I’d assumed that this would be pretty much a one-way thing and though I could hear the repeater, I doubted that it would hear me. But it does! Having the aerial in the right place is absolutely critical (remember that Mr Bean episode when he was trying to position the TV aerial to get a picture?), but once I do – it works just fine. Whereas on FM, my signal into the repeater is just too noisy to be useful. That’s interesting in itself and perhaps you might be tempted to try using repeaters which are a bit further off and see what happens. But the real thought for me was, ‘what can we do with simplex’?
I remember back in the 1980s, having a trip around the BT Satellite Earth station (as it was then) at Madley, Herefordshire. They’d just moved to digital from analogue and were noticing that they needed a lot less power to maintain a steady signal into the satellites.
So, digital simplex ought to work better than a noisy FM signal, or at least until the signal ‘falls off a cliff’. But I don’t think many of us have tried it out properly yet. I know I haven’t! The bandplans aren’t super helpful, jamming all the digital simplex modes onto the same frequencies – but until there’s much more activity, that’s unlikely to be a problem.
When you’re out for a walk with the dog, or up on a hill, or even just listening at home, why not listen on the digital simplex frequencies (which will most likely already be programmed into your codeplugs) and see what happens. Don’t forget to call CQ too! As we know by now, you don’t make any contacts if everyone is sat listening.
If you need reminding about the digital frequencies – 2m on 144.6125 (DMR colour code 1, timeslot 1 and talkgroup 9) and 70cms on 438.6125 (DMR colour code 1, timeslot 1 and talkgroup 9) are good places to start. If you’re a D-STAR or Fusion user – try calling on these frequencies too.
Let’s get a bit more out of all those digital radios we’ve been buying over the last couple of years! It should be fun!