September was a bit of a slow month due to our regular vacation to Gatlinburg, TN and a business trip to South San Francisco. However even with losing two weeks out of the month I still found some time for experimentation.
DMR, or Digital Mobile Radio, is a new mode that seems to be growing like wild fire. Others may recognize MotoTrbo which is Motorola’s take on DMR. While stlll maintaining basic compatibility with non-Moto gear, there are features that may not work when using non-Moto radios with Moto repeaters. However, I have yet to find any such incompatibilities.
Indianapolis got it’s first DMR repeater online while I was on vacation. It’s a UHF machine on 441.200+ (Color Code 1) and has fairly good coverage. As this repeater participates in the DMR-MARC network, it is a Motorola Repeater. The DMR-MARC Network currently only allows Motorola repeaters (XPR8300, XPR8400, etc.) to join because other manufacturers (Hytera for example) do not have a compatible version of their IP Site Connect. Additionally the MARC stands for Motorola Amateur Radio Club, so even if a Hytera repeater were compatible, I’m not sure the politic would allow it to join, but there are talks of trying to do just that.
The interesting thing about DMR is that it takes a standard repeater frequency pair and splits it to two time slots via TDMA. So a stand alone repeater is capable of carrying two simultaneous voice/data channels at one time. Those times slots can be further split up into talk groups, although only on given talk group can be active at a given time. The standard offering here in Indiana looks like this:
TS1:
TG1 – Worldwide
TG3 – North Amertica
TG13 – Worldwide English
TG310 – TAC-310
TS2:
TG2: Local
TG719: Eastern Indiana
TG3118: Indiana Statewide
TG3169: Midwest Regional
For this who are carefully playing at home, you’re probably wondering how two time slots and eight talk groups work. The answer is as you suspect, only one talk group can be active on a time slot at any given time. So while tie model is a based a bit on over subscription, what I see happening is that the broad contacts are made on TS1 and perhaps then transitioned to TS2. I’ve been playing with DMR for the last two weeks and have found it enjoyable and rarely have I been “bonked” when trying to use the system.
I’m currently working with several radios including:
Motorola XPR6550 Handheld
Motorola XPR4550 Mobile
Connect Systems CS700 Handheld (Available to licensed amateurs for $180)
Hytera PD362 Mini Handheld
Hytera MD782G Mobile
Hytera PD782G Handheld (still on it’s way)
Kirisun DP770 Handheld (still on it’s way)
My experience has shown the mode to offer very reliable and good quality voice with great range. I’ve done a lot of ops from an HT with a stubby duck inside of a car miles from a repeater with great results.
For those of you who might be experimenting, I’m usually monitoring the Local TG2 on the W9AMT repeater. And in the spirit of things, if you have any questions regarding the mode or specifically any of the radios I’ve worked with, please feel free to let me know. I’m happy to share what I’ve learned. I’m also updating my website on a regular basis with my findings.
Let’s hope by this time next month we’d not putting down the HT’s and picking up the snow shovels!
