VK1 70 cm DMR activations

Hi all,

This morning at 2320 UTC VK1 SOTA activators undertook the first VK1 simultaneous SOTA Digital Mobile Radio (DMR) activations on 70 cm 439.0125 MHz simplex. Activators include Matt VK1MA at Mt Ainslie VK1/AC-040, Mark VK1EM at Mt Stromlo VK1/AC-043 and Andrew VK1AD at Mt Taylor VK1/AC-037 for what may be the first VK SOTA DMR and DMR S2S contacts on 70 cm.

Matt, Mark and Andrew were joined by six DMR chasers, Dave VK1KV, Graham VK1GVC, Farren VK2XFR, Rob VK1RW, Amanda VK1WX and Bill VK1WPR.

Look out for more DMR activity out of VK1.

73, Andrew VK1AD

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Hi Andrew,’

Good on you and the gang for trying something new. My impression is that it ranks between SSB and FM for capability. I’m not sure, apart from the novelty and new category om modulation, what it would give for the expense of an extra box or the complexity of a computer/sound card add on.


Hi Ron,

My so-called extra box is a programmable dual mode DIG/FM HT. I wonder what the AM mode community thought of SSB when that mode was introduced? I suspect smiles all round.

As for the novelty factor of an open digital protocol, well I suspect it’s here to stay. Long live DMR :slight_smile:


Andrew VK1AD

Ron, I think you may be mixing up DMR with FreeDV?

Think of DMR as the commercial equivalent of D-STAR but with not as many features (at least not yet - they are coming). In many countries D-STAR repeaters are being replaced with DMR ones. DMR started in Motorola mobile rigs as Moto-TRBO I believe but is now produced by several commercial radio producers as HTs and Mobile rigs and some companies are building rigs that now cover the amateur 2 metre and/or 70cm bands. I believe in Dayton some Chinese DMR HTs were for sale around the $100 price point.

As shown here, like D-Star the rigs can operate simplex or via repeaters. In the case of SOTA contacts they have to be simplex of course.


I’m sure that SOTAwatch has a DV mode but the database does not. Log the QSOs as other and if you are going to make digital voice contacts regularly I’ll look at adding the mode to the DB.

Wasn’t S2S but I did some DMR and P25 contacts on VHF and UHF respecitvely in VK2 about 12 months ago with some suitablly equipped chasers. The more modes etc the merrier I reckon.


I well remember the open warfare between the “Donald Duck Brigade” and the “Ancient Moders” which arose because the two modes were incompatible. SSB won out in the end because it has a clear advantage over AM, but (a) it had to demonstrate that advantage in the real world, and (b) take-up was gradual because it made a lot of expensive equipment obsolete - ham gear cost a lot more in absolute terms in those days although many used inexpensive ex-WD equipment.

People may doubt the benefits of DV but the rancour of the 1950’s is unlikely to recur!


One advantage of HF digital voice in the form of CODEC-2 powered FreeDV is that it uses half the bandwidth of SSB and as such we can get twice as many stations in the same space. A relevant point given the WRC15 5MHz 15KHz allocation.

Other VHF type digital modes - D-Star, DMR, Fusion, APCO-25 etc. are not suitble for use on HF as they require more bandwidth than SSB.

FreeDV still requires development however, so I don’t see the death of SSB happening for some time.

73 Ed.

I shall watch the development of FreeDV with interest but am not ready to order an SM1000 yet!


Hi Brian - agreed. The SM1000 is a great way to add FreeDV to an existing SSB transciever but is a little large and (IMHO) too expensive. I run FreeDV from a PC using the same interface required as RTTY PSK31 etc.

Of course those with Flex systems already have it in the software on those rigs.


Except you can’t understand what any of them are saying because, to date, ALL low bite rate voice codecs sound mince.

I have heard D-Star simplex at worse quality than good quality FreeDV/CODEC-2 but that is definitely the challenge to keep bandwidth down which increasing the quality of the audio. In my experience using a good microphone (not any old PC mic.) with FreeDV makes a major difference in the quality of the received signal.

73 Ed.

Hi Andrew,
Ed is right, I was thinking of FreeDV as I did not think there was enough uptake of the Motorola system to qualify a peak. DMR is a good mode no doubt, for some purposes. I am not adverse to a new mode if it does something for me. I ask not what I can do for DMR but what DMR can do for me.

For example I adopted SSB because it had a 9 dB gain over AM and I really wanted to work some of that 2 m dx with gear that I could afford and could build. I have gone back to CW because I really want to work some of those weak SOTA stations. (another 10 db?)

I have used FSK441 to work some more dx on 2 m. I use JT65HF on HF to get DX contacts when band conditions are poor - as they are now. It is painfully slow but brilliant with very weak signals that are below the CW threshold.

I have tried FreeDV on HF. Unimpressed. In it’s present form it can’t handle selective fading.

I use FM when mobile and for occasional local contacts. It is a chatter mode IMO, not that there is anything wrong with that.

I have DStar capable radios and have had a contact by that mode. It has techy bits but it doesn’t offer any improvement for what I’m currently doing.

I have been to a lecture and demo of DMR. Excellent technology but I could not see why I would get anything for my investment. I was hoping as a SOTA user you might have a different angle.

For commercial operations DMR has a use; the ease of interfacing with internet and other digital based systems and the reduced bandwidth all make sense in a commercial environment. The number of repeater channels and simplex channels can be effectively doubled by switching the technology. If our amateur population were increasing then that might be the pressure point, but not now.

The power drain is apparently less than for FM but it will still be more than a CW rig and maybe the same as an SSB rig. Any informed comments (but not conjecture) will be appreciated.

Some amateur radio history.
AM, FM and SSB were all invented about 100 years ago. AM offered voice operation at a price that amateurs could afford from the 1930’s on. A bit of drift in the carrier frequency was acceptable. FM only got going when decent VHF tubes became available, the HF band was too crowded for that stuff! SSB had to wait until very stable VFO’s were developed some 65 years ago. SSB was first used commercially in bulk to put multiple voice circuits over a pair of telephone lines. See if you can find an old telephone technician to explain Groups and Super Groups. The point is that historically a technology has only been adopted in general use when it offers a solution to a problem.

DMR seems to offer me a solution for a problem that I don’t have yet or am unaware of having.

Please don’t take my lack of personal enthusiasm to take up Motorola’s system as criticism for anyone wanting to experiment with it. If it really takes on you will be an early adopter. If not well you’ve had a go.at something new.


Great, Andrew! Good to hear, that there’re some other activations being done with digital voice modes. I’m always carrying various digital HT’s with me (DMR, TETRA, APCO P25, Fusion, D-STAR), also during SOTA activations.

But it’s always difficult to find somebody for a simplex contact. Until yet, I worked chasers on TETRA, DMR and D-STAR from two or three SOTA summits in simplex on UHF, e.g. DC5CC in TETRA and DMR from DL/MF-079, Wendelstein (SOTA Database).

DMR, TETRA and APCO P25 radios have to be programmed in advance using a CPS with the right frequencies and talkgroups, timeslots, ColorCodes etc. It’s important to program the national CoA frequencies for simplex in advance. (Germany+Austria: DMR (TS1 TG1/TG9 CC1) and C4FM: 433.450 MHz, TETRA (MCC:901 MNC:16383 GSSI:1): 430.4125 MHz). Keep that in mind.

I’m really looking forward to more DMR, TETRA, APCO P25, Fusion, D-STAR chasers! :slight_smile:


@MM0FMF I’ve logged all my simplex digital QSO’s from a SOTA summit whether PSK31 on HF or DMR, TETRA, APCO P25 and D-STAR on UHF as DATA. From my point of view, there is no need to add other modes to the database. Otherwise you would have to add hundreds of different digital modes on HF, VHF, UHF and SHF.


Thanks for the comment Jakob. The reason to have DV (digital voice) section is to distinguish them from pure data operations. There is a “Tower Of Babel” of digital modes and I don’t intend to have PSK31, PSK127, MFSK8 et. al. We have a variety of voice modes (SSB, FM, AM) so it seems reasonable to add DV for all specific digital voice modes (DStar, DMR, System Fusion, TOC-H, UTCAA etc.). Then we can distinguish use of digital voices compared againt digital ‘RTTY’ type modes.

I think, I haven’t checked yet, it is a few lines of C# to change. So it isn’t a huge change or amount of work and can neatly be smuggled in with some other changes that I will be doing soon.

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Thanks Andy, it would be nice to be able to differentiate between digital data and digital voice - I have previously entered DMR contacs as “OTHER”, but it would be nice to be able to put them in as voice contacts,

If there is to be a generic term for digital voice modes, I am a little uncertain if we should describe them as DV (even if that is technically accurate) as I thought that the DV codec was comonly referred to as DV, potentially leading to confusion

Agree that having all the modes both voice and data would make it harder for you - but conversly, if we are to move towards other file formats for log submissions (like ADIF), wouldn’t it make it easier if all commonly accepted modes under the ADI format logs were also accepted in the SOTA database? I freely admit that I have no programming background, so not speaking from a position of knowledge here!


The log parsing code looks for things it knows and puts them in the right place so USB or LSB become SSB and RTTY becomes DATA. FM, AM and CW are handled. If it finds something it doesn’t know, such DSTAR, then it puts it under OTHER. I was going to add (for the sake of argument) a DV category on the drop down and then tweak the parser (used for log uploads) to lump a variety of digital voice modes under DV. So DSTAR, DMR, P25 & UTCAA would be dumped into DV.

Now some people may wish to differentiate between the DV modes but at present they make up such a minuscule proportion of the contacts that it’s not worth it. You could argue AM is minuscule and has its own group and you’d be right and I’d agree. That’s just how things are and I wont be changing it. So we will be able to see how the relative use of the different voice modes (SSB, FM, AM & DV) changes as DV modes get more popular. My own gut (and it’s a big gut!) feeling is that the overwhelming majority of DV modes use some kind of repeater/linking and simplex use is low. That doesn’t make this not worth doing. And I’m sure the people playing with DV can do all sorts of experiments showing how DV vs FM works in real world simplex conditions.

That kind of analysis may show DV handhelds are much better than FM. Or not. However, I still maintain that most of the time it sounds like Aquaphibian…


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Hi Andy,

One could of course group SSB under AM, after all it is AM just with the carrier and one sideband removed. Then CW could also go under DATA with RTTY as it is a digital data mode. That would then just leave FM(including phase modulation modes) and Digital Voice DV.

Realistically adding DV to the existing mode groups that you already have should be sufficient and is then similar to what was done a few years back when the logging EDI standards were extended to include Digital Voice.


P.S. I’ve have FreeDV simplex QSOs from here to Austria, Spain and Poland and was heard fine i Holland and the UK.

Where is Aquphibia - perhaps we can have a “cross-mode” contact?

It borders Elbonia.