DMR – A Love/Hate Relationship

[Disclaimer: This is my experiences of two weeks with a DMR transceiver, quite literally that. This blog may contain some holes and may not be entirely concise, and bits of info as a result may contain inaccuracies. Don't take it overly seriously and as a definitive guide]

I've joined the 'dark side' of radio, as they call it on the UK wide talk groups over there. The latest ham radio craze that seems to have swept across the UK like wildfire; with people getting NoV's all over the place and sticking repeaters up just because they can and want a slice of the digital action – combined with “handie's” that only cost in the region of £90 upwards for something imported from China that you have to program up yourself, or have a local friend send you a code plug.

Yes, I've bitched and moaned about digital telephony methods in the past such as Fusion or D-STAR. Yes, I'm fully aware I've gone totally against my original views – the viewpoint of migrating to another transmission mode on VHF & UHF that's already spreading a thin user base even thinner than ever before.

UNTIL – GB7JL opened in Wigan, and pockets of users threatening to dump 2 meters as they're sick of morons, numpties, and pirating dickheads. Which left me with the worrying prospect of 'radio tumbleweed' whistling through 2 meters and 70 cm.

At the time of this particular blog – it's week 2 of owning a Tytera MD-380, the handie that's sparked a veritable DMR revolution in the UK.

First impressions:

What do I make of it so far?

Well, first of all I quite like the Tytera rig. One of the things you'll notice if you've ever had a go of one is that they're far better screwed together than a Baofeng UV 5R, or similar VHF/UHF Chinese import. The Tytera MD-380 isn't just digital only, it also covers 70cm FM – which I suspect from a business user's perspective aids the transition of going from analogue to a digital format and to have a 'fall back' mode if DMR goes down, as DMR is originally a digital PMR system that has been cannibalised by ham radio operators (so far, DMR is 70cm only).

However, there are some quibbles with the transceiver. Off the top of my head, the worst one is that the signal meter half the time appears to have a mind of its own, while programming receive only banks doesn't appear to knock the transceiver down to 'receive only' if you knew a local DMR frequency that you wanted to monitor and use as a form of digital scanner. There's more odd little bugs out there, but they're gradually getting resolved with firmware updates which aren't too problematic to do. Recently, (at the time of this blog) there has been some enterprising ham radio ops that have made some experimental firmware that in effect turns the Tytera MD-380 into a digital scanner. and to instantly QSY when it finds a station transmitting without having to change channel. Although, I've not tried it for fear of bricking it.

DMR annoyances:

The biggest problem with DMR as a format is that it's originally for business users, and not for ham radio purposes, and it shows.

Repeaters are programmed as 'zones', and inside those 'zones' are the 'talk groups' which are in effect your channels to QSY to. For example, if you were on TG230 which is a UK wide group, the general convention is to keep the contact brief and ensuring you QSY to another talk group which would be something like TG80 or TG81. On some repeaters, you also have a 'parrot mode' where you are able to check the legibility of your transmitted audio into the repeater which is TG9900 (if I recall correctly).

Repeaters in the UK usually use one or two different servers that enable UK wide, Europe wide, or Worldwide communication – which come in the form of Phoenix, or Brandmeister. So far, Phoenix based repeaters are easier to work out as you just turn the dial to the appropriate call group. However, Brandmeister requires you to type in the appropriate reflector on the keypad to QSY – supposedly like Echolink somehow, Christ knows. Don't quote me, as I've not fully got my head around it. The repeaters I can access are GB7PN (Prestatyn), GB7HM (Hope Mountain, Wales), GB7LP (Liverpool), GB7MR (Manchester), and lastly GB7JL (Wigan) – just about, as it has a hell of a job getting into my home location of West Lancs as it scrapes over Billinge Hill. The rest I can navigate around, but GB7JL uses Brandmeister and I've no bloody idea how it works – I can't get a straight answer out of anybody about it and ended up with two people bickering over the air on how it should be done. Which resulted in me getting pissed off with the thing, switching off, and making a brew.

[predicted UK coverage, taken from UK Repeaters site, Feb 2016]

You may hear talk of 'code plugs'. This in effect has your unique DMR ID and callsign, which is ALWAYS transmitted with you – nothing escapes the the 'Big Brother' aspect of DMR, and your repeater transmission information which can be checked online. The transceiver has to be registered, and a PDF copy of your licence (downloadable from Offcom) has to be uploaded as proof of who you are to the DMR-MARC website. The DMR system allows the option of remote shut down, remote kill, and even to to force the rig to transmit automatically if the user is in distress or danger. I've no problem with a uniquely transmitted ID, as it in theory should keep pirates and arseholes off the air, however – who's to say the local repeater keeper might turn nasty on you, have a fall out and boot you off their repeater over some totally frivolous reason? Or worse, be one digit out on an ID and disable your transceiver in error? What makes it a nightmare is that not all code plugs you get from sources are entirely accurate, and may be missing information – such as incorrect talk group information or in my case the wrong CTCSS tone for GB3PZ. Which can leave a user not knowing where the hell to QSY to as it isn't in your code plug or theirs, or worse still – a rogue bit of corrupted information that can crash a DMR repeater (this supposedly happened with GB7JL that really pissed people off).

[Current Google map showing DMR repeaters that are active, Feb 2016]

What needs to happen is some form of complete standardisation instead of rogue code plugs flying around that could be missing pieces of information, perhaps complied by Offcom themselves would be a good idea. Right now, the continuous fighting over how it should be done could result in the death of the format if it's not kept in check. Also, it'd help if certain repeater's internet pages were clearer about how they operate as most are clear as mud.

How about making your own code plug then? Nope, all of the nope. If you struggled with programming something like a Baofeng or Yaesu FT897D via a computer then you will find setting up a DMR transceiver 50 times more complicated and very easy to bugger up. I got around this by buying a pre-programmed Tytera MD-380, but even then it had a couple of bits of wonky info that I had to correct (although the Brough Telecom 'v2' code plug I was sent appears to be okay – so far). If you buy a 'blank' one, ensure you get a reliable code plug from someone who already has DMR first and put your user ID and call sign into it. Programming by hand? Forget it.

DMR advantages:

I believe that once the dust settles with the DMR format, it may conquer the other digital telephony methods that are out there – D-STAR by Icom, and Fusion by Yaesu.

The DMR 'codec' is something that Motorola made, called MotoTRBO that has some very clever tricks up its sleeve. The best part is that repeater activity can allow two sets of traffic, taking up 6.25khz of bandwidth versus 12.5khz used for FM. So, it can carry two separate conversations in the same channel which allows for very effective usage of 70cm. People complain of the compressed nature of DMR transmissions, which to be honest remind me a a loud and punchy sideband transmission with a curious vocoder quality – and not as terrible as you'd be lead to believe. Also, an S1 DMR signal is significantly more robust than S1 of FM signal – which at that point will become very scratchy and hard to make sense of. A DMR signal has error correction to a certain point, before it turns a bit 'Norman Collier' and drop outs happen – which reminds me of a corrupted mp3 file. Essentially, it suffers from a steep 'signal cliff' where it would lose everything.

What really interest me as a ham radio op, is to see how it performs under lift conditions such as Sporadic E or Tropospheric Ducting. After all, TV-DX is still possible and often quite legible using DVB-T versus analogue PAL or SECAM – and people already use PSK31 and JT65 where normal telephony may fail. I dare say I'm tempted to make a 70cm band beam just to see what the hell it would do for a laugh!

One of the things I like about DMR (even though the purists say it's against the spirit of ham radio) is the linked repeater capability so that people can speak to UK Wide, World Wide, or Europe Wide – and (so far, don't quote me precisely) experimental 'roaming repeater' options for mobile operators. Yes, it's 'cheating' – but you are still using a form of radio, and let's face it – due to coming out of sunspot peak years has made HF bloody awful for days on end unless you're running a 60 ft tower, Cushcraft beam, and a kilowatt. Another important aspect for me is that under terrible band conditions, you can still 'play radio'. Also, it has advantages for people who are living in sheltered accommodation who can't put up overly elaborate antenna systems. It'd certainly keep old Bert happy who had to move into a home, who used to enjoy going on 40 meters and 80 metres nattering to the boys – as long as he had a Grandson to keep his Tytera up to date, that is.

Will I be ditching it all for DMR?

No way!

For me, it's just another transmission mode to doodle about with – that if it wasn't for GB7JL opening up I wouldn't have originally cared less about it. I often use a handie while going to the girlfriends gaff,or cycling where I've had a repeater signal and no phone signal. DMR has added another dimension to portable radio operating that would not have otherwise been possible with my Baofeng UV 5R on 2 metres and 70 cm FM.

Lastly, will it kill off D-STAR or Fusion and should you buy one?

The biggest problem with Icom and Yaesu is the huge expense of the transceivers for something just to talk locally on with 2 metres and 70 cm (excluding that Icom rig that can do HF D-STAR). Icom and Yaesu are too possessive with the codecs, and won't let anybody make a transceiver using them (as far as I'm aware). However, DMR – or to be more precise MotoTRBO is designed by Motorola and there's quite a few transceivers that use it and they're not that possessive over the rights. Currently, various radios exist made by Hytera, variations of the Hytera brand (Tytera, Retevis, etc), Connect Systems, and Motorola themselves (the Motorola transceivers are the absolute kings of the DMR game, sound amazing, cost an arm and a leg but are totally worth it).

DMR can be obtained for as little as £90 upwards, while D-STAR and Fusion is at least £350 to start with – which has made DMR very attractive and very affordable, which is why it appears to be a runaway success in the UK.

D-STAR and Fusion to me are Betamax (a good system that's badly marketed), while DMR is VHS (a not entirely perfect solution, but one that will be hugely successful due to cheap cost and the TDMA system that allows for twice the radio traffic in the space of one channel).

To conclude, if you don't have a DMR transceiver and you have repeaters that cover it near to you that you can access – then give it a whirl. It's a particularly cheap and interesting gateway into the realms of digital telephony methods, that won't break the bank. The quibbles will be ironed out and improve over time.