Getting into DMR
A local amateur got in touch with me after spotting my callsign on the local DMR repeater logs, asking for advice on the new digital mode. I've reproduced my reply (from March 2015) here to help others considering going digital.
Hi Nick, Can you give any advice on the DMR system? Is it busy? What antennas are required? Is it worth getting? I do have D-STAR, I find the Digital radio system interesting. Hope you can help.
Yes you are correct, I recently got myself a DMR radio (Motorola DP3400) and now work the world through local repeater GB7EX.
Compared to DSTAR, the audio on DMR is a little better, but it doesn’t have some of the more advanced features that DSTAR does (like IP networking).
Being a new system, it’s still growing. Most DMR contacts happen through the DMR-MARC repeater network (400 repeaters worldwide, 37 countries, 10k operators). You can work DMR simplex, but it’s as rare as someone calling CQ on 70cms.
It’s a busy network, there are both UK and Worldwide nets at set times, and most of my calls get answered quickly. It’s nowhere near as busy as HF, but if you call, you’ll probably be answered. There’s a live view of DMR repeaters and stations — each row is a TX.
Actual operation is a lot simpler than other digital modes — there’s no need to dial in specific routes; each repeater is set up with a number of Talk Groups. For example, Local, UK Wide and Worldwide. You program these into your radio as channels. To talk UK Wide, you just tune to that channel and transmit. I’ve attached two pages from a recent demo I did at the CARS Skills Night that show the Talk Groups (TG).
As for antenna, DMR simplex and DMR repeaters are in the 70cm band. The DMR calling channel is 438.6125MHz, and GB7EX’s repeater input is 430.7125MHz and output 439.7125 MHz.
Being close to the repeater, I can work with the radio’s rubber duck, or a mini-mag aerial meant for 2m & 70cms mobile. I’ve seen others make up a Slim Jim antenna to the correct frequency. If you already have a dual or tribander at home for 70cms, you should have a reasonable match.
Personally, I enjoy DMR, but I bought a very basic radio (£130 secondhand from a security firm on eBay). It has no screen, and a selector knob on the top to switch through repeaters and talk groups. While some more complicated radios are starting to come out (CS700 from China, Vertex/Yaesu), only Motorola radios are guaranteed to work, and IMO of good enough quality. DMR is a Motorola system, built on their commercial radio repeaters, and they’ve essentially had years head start on designing/testing radios.
My best advice here is it’s early days for DMR, so to either go for a Motorola, or wait a little while for the other manufacturers to hit the market and soothe their teething troubles.
My final point on radios — the downside of a Motorola (and there are Motorola radios with displays, I picked the cheap option), is that they need to be programmed by someone who knows what they’re doing, and who has the Motorola programming software meant for commercial radio dealers. Unlike the competition, this isn’t something you can download and do yourself — the software is locked down and only provided to dealers. If you’re buying from a site like Ham DMR, they should program the radio for you, just be wary of any kit from eBay.
Anyway, appreciate that’s a long reply — hope it helps!
73, Nick, 2E0DVX
Update: Things move fast in DMR…
Another amateur got in touch (June 2015) to advise that non-Motorola kit is now working well with the DMR MARC system. If you're interested in trying a cheaper, full-featured radio, Paul (G7BHE) has a great review of the Tytera TYT MD-380 on Essex Ham.