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last updated 18 Mar 2006

DMR 446 - D-PMR - Digital PMR446

On the 28th October 2005 the ERO released decision ECC/DEC/(05)12 detailing a new 100kHz block of frequencies (446.1-446.2) for a digital variant of PMR 446 to work alongside the existing analogue system (446.0-446.1). This will provide 8 radio channels with a 12.5kHz spaced standard, or double that number with a narrow-band system of half the bandwidth (see the frequencies page on this site for specifics).

I have seen many comments already about this being complete overkill for the purpose! The existing systems works perfectly well enough. What advantage(s) will DMR bring?

It remains to be seen what sort of equipment we end up with. Will we still manually deal with channel numbers and some new sort of privacy codes - or will things be more automatic and abstract? Perhaps we'll have text messaging, automatic free-channel selection, talk groups, each radio having an ID that allows you to manually include or exclude specific radios from your group? We will probably get full duplex (like a phone call).

If an open standard (non-proprietary) emerges that has significant advantages over analogue FM (for marginal / weak signal working) it will probably end up adopted for amateur radio too, so I'm watching this evolve with keen interest. Suppose that for a given contact FM is too noisy to be readable, but the new digital system would allow good copy - that would be a good reason to adopt it to replace FM for cheap and simple mobile use (adding a new chip and supporting circuitry to a simple radio is less fiddly in many ways to implementing SSB). In the real world though, I expect that at low signal levels the station you're trying to listen to will end up breaking up with loud clicks, weird noises, dalek effects, or 'boiling mud' syndrome if DSAT, DAB and GSM are anything to judge by. This will be so annoying that amateurs would rather stick to good old tried and trusted analogue modulations.

I remain sceptical that digital two-way radio will be acceptable at all, to be honest. Even fairly strong FM contacts have their breakups as the signal momentarily dips to nothing and back, and I'm sure this new system will cope gracefully with that.. but everyone who uses simplex two-way radio ends up making a lot of difficult contacts at the limit of the range - it's unavoidable. We're all used to noisy signals and moving about to get a better signal - we can judge the quality by the amount of noise. With digital though we don't have any clues what's happening - it's either fully there or it's going badly wrong, with no way of telling when it's about to happen or how to judge whether it's possible to improve matters or just give up. I suspect a lot of people are going to find digital two-way radio too annoying to use. They will be expecting it to JUST WORK and will be very frustrated when it all breaks up and appears to be broken and unreliable. This is a digital solution FOR THE SAKE OF IT - an answer to a problem that doesn't really exist. The industry has had reasonable success with GSM and TETRA where the mobile units are working within clearly defined areas well served with a good signal level from base stations, but I remain to be convinced about the viability of handheld-to-handheld digital radio. Not unless the system generates some noise to simulate fading reception - to give the user some idea that the signal levels are getting too poor to EXPECT good results. I hope my doubts turn out to be wrong, but I've too much weary experience of so many other good analogue things being replaced by disappointingly mismanaged digital replacements.

"ETSI has developed ETSI Technical Specification TS 102 361-1 for digital PMR 446 equipment with 12.5 kHz channel spacing and TS 102 490 for digital PMR 446 equipment with 6.25 kHz channel spacing, both FDMA systems using either a 12.5 kHz bandwidth according to ETSI TR 102 335 1 V1.1.2 (2004-10), or using 6.25 kHz bandwidth according to ETSI TR 102 433. In the future there may possibly be other systems covering digital PMR 446 applications. ETSI has already developed the harmonised European standards EN 300 113 2 (12.5 kHz bandwidth) and EN 301 166 2 (6.25 kHz bandwidth) for radio conformance purposes.

That the preferred date for implementation of this decision shall be 1st February 2006 (France may delay their implementation until 01.01.2011).

ETSI TR 102 335-1 V1.1.1 (2004-06) http://webapp.etsi.org/action/PU/20040629/tr_10233501v010101p.pdf

Mentioned http://www.ero.dk/9E8335C2-0CD2-41C9-8B44-2C15D8BFDAB4.W5Doc

Icom on the case http://www.icomamerica.com/press/?id=20050406
- Icom and Kenwood have jointly developed a very narrowband 6.25kHz digital communications technology using an FDMA 4-level FSK modulation method.

Discuss : groups.yahoo.com/group/DIGITAL2WAYRADIO/


Licence-Free Digital

Either 446.1MHz D-PMR or other.. 2.45GHz..

ICOM

F4029SDR EXTERNAL PIC (OR LOCAL)
First DPMR (mar 2006) - 16 digital (4FSK/FDMA with 254 "common ID" codes) and 8 analogue ch (+50 CTCSS/ 84 DTCS). 400 euros price level.
280g inc batts, 53x195x32.5mm inc antenna, aluminum die-cast chassis, mic socket 3-pin connector / 2.2 KOhm, spkr socket: 3-conductor 3.5 mm / 8 Ohm.
Batts: Li-Ion 7.2V pack (6AAA pack BP-240 available)

see http://www.marcucci.it/english/prodotti/schede/scheda.asp?ID=13410
and http://www.446user.co.uk/forum_topic_2995.html


Motorola

DTR2430 / DTR2450 EXTERNAL PIC (OR LOCAL)
(announced in March 2006) Frequency Hopping Spread Spectrum radio that works on the licence-free 2.45GHz band, with 100mW. "The two radios are similar in features, but the DTR2450 is ideal for managers and decision makers as it offers the ability to monitor, manage and programme their teams radios". " changes frequency 11 times per second and sends each data packet 3 times"

see http://www.446user.co.uk/forum_topic_2986.html

DTR 410 to DTR 650
A range of similar radios working on the US ISM band at 902-928MHz (UK has 886-906MHz for ISM). 1W. 50 'FHSS groups'.