dPMR/Analogue Compatible Radios

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dPMR/Analogue Compatible Radios

Postby 108rt003 » Fri Aug 18, 2017 9:13 pm

Hi All,
I am contemplating trying out the dPMR digital voice mode, to be clear I am NOT referring to DMR, but to the system as standardised in Europe as DPMR using the 446Mhz frequency range, that is FDMA (frequency division multiple access) using the AMBE+2 vocoder. I do not know if there is an equivalent system in North America.
I have searched on the interweb and there are many China radios which state that they are dPMR radios, but further investigation highlights the usual Chinese manufacturers' propensity to spurious facts, errors and lies with many so-called dpmr radios turning out to be DMR (i.e. TDMA ( Time Division Multiple Access )) system radios or
if they are using the FDMA system, their vocoders are not compatible with the standard AMBE+2 adopted in Europe.
I would like to be able to program the radio with the frequencies I required (most probably the European 446PMR analogue and digital frequencies and amateur radio analogue and digital frequencies) and so the radio would need to be able to cover the 70cm amateur radio band (and 2m band if dual band) and the 446Mhz PMR frequencies and in particular to be able
to be programmed with the odd 446PMR channel frequencies with 6.25 KHz channels (for example, 446.00625MHz, 446.01875MHz, et cetra on analogue and 446.103125MHz, 446.109375MHz, 446.115625MHz et cetra on digital).

I am wondering if there is anyone out there using/hearing of such a radio?

REQUIREMENTS

Digital using FDMA (frequency division multiple access) using the AMBE+2 vocoder
Analogue FM
Capable of working on the 6.25KHz channels of the European PMR and dPMR system
Capable of working on the 70cm amateur radio band
Programmable either via computer software and a programming lead or via the radio itself it easy

The TYT DM-UVF10 radio appeared to fit the above criteria, but I believe that the channel spaces available are not compatible with the 6.25KHz PMR channels, so that the channels wouldf not be programmed correctly.

Thanks for reading and sorry for the long email, but hope someone out there might have experience of such radios?

73 and hope catch you on the bands sometime

Robert
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Re: dPMR/Analogue Compatible Radios

Postby G4RMT » Sat Aug 19, 2017 11:58 am

I have some dPMR FDMA kit - S760, mobile 10W kirisun 680 and the very cheap, 16ch anysecu 280s - all these talk to each other fine. All can cope with ham band 70cm, the usual business radio channels, and if you don't mind breaking rules, PMR446/DMR446 channels.

In real terms, this lot, plus my Kenwood NXDN and the DMR stuff all perform about the same, in terms of performance. They all sound a little weird, but you get used to this quite quickly.

I suppose it really boils down to what you wish to do with them, and who you need to talk to.

I'm convinced that the real differences are due to the bells and whistles, and not basic performance - in terms of distance or audio quality. We're really into beta vs vhf again. None of these radios would be on my DO NOT BUY MORE list. If you have no real need to share a single frequency as with dual slot based DMR using a single 12.5KHz channel, and can live with two channels side by side in the same bandwidth - there's very little difference.

I did make one very basic mistake when considering some of my first digital purchases. Repeaters. It is not made at all clear in my opinion. One repeater on DMR is two discreet channels - one antenna system - two simultaneous users. The same thing on dPMR needs two repeaters. The sales blurb often indicates fnma, says dpmr and then you see two slots - an A channel and a B channel. You know then it's TDMA. Buyer beware. The good thing is that the genuine dPMR repeaters usually auto switch between analogue and digital, although I suspect they simply repeat anything on the input, no matter what it is, and simply the receiver switches for outputting audio. Lots of these products also seem to use two hand-held radios inside, hot wired to extract discriminator audio, and LED 5V info, then just reinject this to the TX. Works fine, although because it's actually doing D-A, then A-D, the audio quality is slightly worse than a d-d path.

I've given up trying to get my usual chinese suppliers to appreciate the distinction as they really juts shift cardboard boxes without understanding what is in them.

What are you up to then? DMR, I suspect is just simpler in equipment when you use repeater networks, so it will be always better in that department. You can actually read this in some DMR/DPMR documents when it talks about the reduced equipment count, but the FDMA brigade of course ignore this important feature - their selling feature is simply very narrow band operation, but any repeater networks will cost more - either splitters and combiners and then single antenna working with reduced cabling costs, or double the antennas and cable costs and forget the splitter/combining networks. A more sophisticated proper dual channel repeater can in fact work out cheaper.

Although I believe it to be the case, I'm not actually certain that all the Chinese DMR repeaters can actually use both slots simultaneously - the repeater I was considering did not actually confirm this - one of the cheaper versions, so I wonder if this is a two portable radio type inside, and the slots are programmed in and you have pick one OR the other. Maybe somebody has one and can comment?
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Re: dPMR/Analogue Compatible Radios

Postby moj » Sat Aug 19, 2017 2:36 pm

Good explanation G4RMT , there's also the icom dpmr sets like the ic-f4029 sdr that uses the similar format to kenwood nexedge etc that were brought out as the digital pmr sets and i've played with the kirisun's and also own nexedge radios and you can see how the Chinese tried to duplicate everything then theres the cheaper ranges which are more fdma standards as you say .

I was impressed with the audio tho compared to a dmr set when I expected it to be not as good quality etc .
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Re: dPMR/Analogue Compatible Radios

Postby 108rt003 » Sat Aug 19, 2017 4:49 pm

Hi G4RMT & moj,
Thanks for your replies.
I am interested in all types of radio and have had analogue 446PMR radios in the past, on D-Star and DMR at moment.
You get a few enthusiasts on the 446PMR bands and had a few (not a lot) QSOS, so with the advent of digital, I thought I might give the dPMR part of that band a try, but don't fancy splurging out on the Icoms (and possibly Kenwoods) as there is not that much activity, but with all these Chinese digital radios now appearing which cover the amateur bands as well, they look more interesting.
My problem with them, is as you say G4MRT, they can be a little (sic) flexible with the truth when describing the abilities of their radios and many "dPMR" radios, when you look into their specs (if you can find them) turn out to either NOT be dPMR (FDMA), but DMR(TDMA) and if they are they are some Chinese vocoder reputed to be AMBE+2 but turns out to be a "Chinese copy" not compatible and are not capable of the 6.25KHz channel spacing unique to dPMR .
Okay on the rigs, G4RMT and moj, I will look up the models you listed and see if compatible with the EU dPMR on 446 AND 70cm amateur band. Plan to keep on low power, the 446PMR power level is 500mW, but obviously the higher power on 70cm. The anyescu 280s sound any idea (cheap), if they are programmable reasonably easily and have the right channel spacing and cover the 70cm band they might be what I am looking for.
I want to try out the band, see what is there, see if can get some activity, but having the amateur bands hopefully gives a backup in that I can be assured of activity (as much as current activity levels mean) and avoid the rig just being a brick.
I noticed that NXDN and Fusion as both FDMA, so I assume the difference between them and dPMR is the vocoders.
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