APRS over DMR with a Motorola XPR radio

     One fun part of working with commercial gear is the limited number of up to date resources on how to get the radio working with amateur radio systems. And one of those big pains for me was getting APRS to work via a Motorola radio. Motorola radios that have GPS are designed to report station location and current channel back to a central dispatch center, but some very clever hams in this hobby have made that system work through Brandmeister. Most of the guides I have come across have been relatively out of date, or would tell you thirteen different ways of doing it. By combining bits and pieces of each one, I have gotten my APRS location to successfully report via a hotspot and a Motorola HT. I am currently waiting on the results of using a mobile with a fixed repeater in town. 

    The radios I have used are a Motorola XPR 6550 DMR UHF handheld, and a XPR 4550 DMR UHF mobile. I have followed the same steps with my mobile radio, and will post an update if that was successful. However, here's how I got the HT and hotspot to play nice.

    Step 1: If using a hotspot, you will need a Duplex hotspot. There are people much smarter than me that can explain why this only works with a Duplex hotspot, but I was never able to get APRS to successfully transmit via a Simplex hotspot, nor could I get DMR texting to work. My guess is the Motorola listens for a confirmation of a sent text message or location, plus, they are designed to work with some sort of repeater system 99% of the time.

Starting with Brandmeister Self-Care, here are the settings that I used. 


Set your brand to Motorola, your APRS Interval to a preferred time, your APRS callsign (make sure to use an appropriate SSID), and you can set your APRS Text to whatever you want. The only switch I hit here was for the Compact/CSBK data. Depending on your exact model of radio, your results may vary. If this doesn't work at first, try and disable the Compact/CSBK data switch.

Next, I loaded up CPS 2.0 and made the following changes:

General Settings:
-Enable GPS/GNSS

Network:
-Set CAI network to 12
-Set CAI group to 255
-Set TX PDU size to 1500
-Set your telemetry port to 4008
-Set your ARS Radio ID to the first three digits of your Brandmeister master, followed by 999. For example, in the United States, use 310999
-Set your ARS UDP port to 4005
-Set your TMS Radio ID to the same as the ARS Radio ID
-Set your TMS UDP port to 4007
-Set your Beacon Interval to 60 seconds (I do not know if this setting will clash with the interval setting on Brandmeister Selfcare. I just left both of mine at 60 seconds.)

Zones/Channels:
Here's the fun part. You will have to edit every channel that you want to broadcast APRS through. I used the following settings for each channel (talkgroup) in my zone (repeater/hotspot)

-Enable IP Site Connect
-Enable ARS On System/Site Change (This will report your location every time you change channels. Not sure what just ARS On System will do)
-Leave Enhanced GNSS/GPS Unchecked
-Compressed UDP Data Header: None
-GNSS Revert Zone: None
-GNSS Revert: Selected
-Check TX: Data Call Confirmed

After writing the codeplug, I checked my hotspot's activity log. 310999 would call out to my radio for location information, and my radio would automatically report to 310999.



A few minutes later, I checked APRS.fi, and for the first time, I was able to see my icon on the map!


Full warning, your results may vary. I just got this working about an hour ago, and wanted to at least document my findings in hope that someone could get their MotoTRBO on DMR APRS. Every radio is different, and I certainly hope this will work out for you. I've been messing with this system on and off for months, and would be glad to help out if someone needs a hand with this. Send me an email at admin@n1of.com

Good luck and 73,
-Scott




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