Continuing to explore Digital (Amateur) Radio

Well it’s been a while since my last post on digital radio. And as expected, things have moved on.

I now find myself with four Jumbospot (MMDVM hotspots), and an equivalent four digital radios. In addition to the Anytone 868, I now have a Retevis RT3S, a Yaesu FT-70D and an Icom IC-E92D. In short I have all the (in my view major) digital modes covered (DMR, C4FM and D-Star).

I now normally monitor CQ-UK on C4FM, REF001 C on D-Star, Brandmeister TG 2350 (as G4EID) and TAC-310 as KM8H (although using my UK call on voice) on DMR. This may seem a little excessive, but I like keeping all options open. But it has presented with challenges (or ‘learning opportunities’) along the way. First, you can’t really operate (simultaneously) with two DMR radios using the same DMR ID. I’m lucky I was able to use my US callsign on the second radio. The caveat being that any voice ID has to be with my UIK call. Second, there’s a tweak you need to do when entering your DMR ID in the different hotspots. It seems you use your DMR ID and add 01, 02, 03 etc for each different one. Well it works for me anyway.

Since I have four hotspots, what frequencies do I use? Well there are the two allocated (in the UK) frequencies, 434MHz & 438.8MHz. In addition I’ve chosen to use 434.5MHz and 439.975MHz. it’s interesting to see what others are using, and it appears I’m not alone in choosing the above options. The main thing is to avoid the satellite sub band and existing allocated frequencies.

I’m sure some might suggest why I don’t use just one hotspot and have it scanning all three modes? Well yes, that (technically) would work, but all radios would then be on the same jumbospot frequency, and the result I find of that, is that while one ‘mode’ is transmitting (and being received on one radio) the other radios make the most dreadful racket which I can’t seem to silence with any squelch method at the radio’s disposal. Plus, as you’re listening to one mode, you can miss calls on the other modes.

I have a fairly regular contacts with a couple of local amateurs, but tend to drop into listen mode on the other reflector(s) and talk groups. There can be some very interesting QSO’s to listen into 🙂

So, now I’m settled, I do intend to get on a little more now, digital radio offers some excellent opportunities to having world wide contacts without having to have substantial aerials outside.

If you hear me on at anytime, please give me a shout!

73, Mark, G4EID / KM8H.

Digital Mobile Radio (DMR)

I guess it had to happen sooner or later. It’s over ten years since I got involved with internet linking on Amateur Radio with IRLP and Echolink. But I was never really swayed by the upcoming digital modes. At the time D-Star appeared to be the front runner, and since then there have been others, including (probably) the two most popular other ones, Fusion (C4FM) and DMR. But Analogue was (and probably still is) my preferred option.

However, things move on, and I’m now developing an interest in DMR. For those that understand the technology, it’s essentially a time division multiplied system that splits one 12.5kHz channel into two 6.25kHz ones. From a telecoms point of view it’s something I’m very familiar with, but the implementation of it for Amateur Radio is another thing. In my experience the best way to learn is to play. So I’ve acquired a couple of pieces of kit which will allow me to do just that.

I’m now reading up about it, and as ever, as with other aspects of the hobby, there are various ‘factions’. Straight away I can see there are two variants I can use, both of which in their own right are I’m sure perfectly fine. But it’s one or the other. Both will have pros and cons. What I need to work out is which one is the best for me. I then need to work out how to programme all the options. This may take some time. Anyway, within a few days, expect to see G4EID appear on one or other of the DMR systems.

73, Mark.

Short Wave Listening, then and now.

I should probably count myself lucky. My interest in radio started with short wave listening in the late sixties, a time before the age of the microprocessor, let alone the internet. A time when the twisted copper pair, owned by the then GPO (General Post Office) was used to deliver no more than just a standard analogue phone service. Those halcyon days of giving “three rings” to signify something significant, like I’m ready to be picked up, or I’m setting off now.

It was during this time that I would spend hours tuning around all the different short wave bands to catch that elusive South American tropical band station on 60M, or some North American medium wave DX with a home made loop antenna constructed from bamboo canes and the windings of transformers I’d scavenged from scrap equipment at local factories. Once I’d saved a little pocket money, plus any money I’d received for birthdays and Christmas, I’d buy another cheap, ex forces radio, one of the many that were available on the surplus market. All this long before I decided to get my amateur radio licence when I was 16.

Anyway, I digress. The reason for this post is to highlight that today, in a normal suburban location like mine, it’s now all but impossible to listen to the short wave any more. Back then the simple difference was that the only sources of noise on the bands, besides natural noise such as static and lightning crashes, where things like TV line timebase, badly suppressed ignition systems on cars, motor cycles, and worst of all in the summer, lawn mowers. But all those sources were transitory. Once the car had passed, so had the noise. There was virtually nothing in the house that would impinge on the ability to listen to the short wave bands as nature intended.

Nowadays, many devices in the house are connected, with wifi and bluetooth etc. And worse, most now employ switch mode power supplies that simply ooze interference. Sure, there’s the CE mark. But who doesn’t buy cheap stuff off Amazon? I’ve recently pulled apart some of this kit and found that the design and construction certainly doesn’t meet the accepted standards required to suppress interference.

Lately, the standard (easiest) way of distributing the internet around your house employs PLT, which allows you to (for example) place a remote set top box in another room. The technology uses your house wiring and as a result broadcasts constant noise and harmonics right the way up to 100MHz. So it’s hardly surprising that you can’t tune anywhere now without hearing a constant racket across all the bands. The same technology is used to deliver the internet to you down your phone line. If you’re to be able to even hear anything, you’ve to look to digital signal processing techniques just to make a dent in the noise levels.

I guess the only satisfactory method of getting “clean” airwaves is to take a portable radio out to middle of nowhere and try from there. But that defeats the joy of armchair listening, something which I recently thought I’d try and get back interested in. I’ll try things like getting the aerial away from the house, but then it’ll be closer to another house and hence back to square one. As an experiment I recently powered the radio from a battery and cut (well not literally), the mains to the house. The noise did drop slightly, but I was still picking up all the crud from the houses nearby.

So, the latest copy of World Radio TV handbook (2018) I just got may have to gather dust. It’s unlikely I’ll ever hear anything like I used to be able to. Interestingly one of its lead articles this year is all about noise, and it too concedes that it’s just the way it is now.

Of course I love all the technology that today brings, and no, I wouldn’t want to go back to the good old days, but everything usually comes at a cost. And today, one of those costs is that I can no longer listen to the short wave bands.