Winston Lawrence

KD2WLL - Amateur Radio Notes

RT73 HowTo:
A Minimalist DMR Codeplug design.

Retevis RT73 Configuration and Firmware at the time this was written..

 Name Description
 Model Number DR300UV
 Firmware Version 109E.D4.EARSAB.007
 Version Date Nov 27 2020
 Firmware ID DRS-300UV

Now that we have a way to dynamically key up a talkgroup and place the radio into promiscuous mode we can put these two things together and drastically reduce the size and complexity of our codeplugs going forward. This isn't necessarily a new idea. I found out about it while watching Jason Johnstone, callsign KC5HWB, producer of Ham Radio 2.0 [ episode 528: How to write a DMR codeplug in 2021] where he discussed doing this very thing albeit with an Anytone radio. Thanks Jason, I'm paying it forward - (or maybe that's backwards?)!.

Anyway, I wanted to give it a try. I've only had my tech license a few months but have already acquired three DMR radios all of which have different CPS requirements and since the number of contacts (read talkgroups) across the three DMR radios, two hotspots and 4 local repeaters was becoming unwieldy this approach looked good.

I have about 130 talkgroups that look "interesting" on the Brandmeister network and about 80 that look interesting on the TGIF network. Add in 3 or 4 local talkgroups on each of the four repeaters that I have programmed and then factor in two (or more) duplicated talkgroup numbers (i.e different networks/repeaters may have the same talkgroup number assigned to completely different groups) you can see that setting up a codeplug to cover even a subset of the talkgroups can be challenging. You can look at Jason's video where he explains it better. The idea of creating one spreadsheet based cheat sheet with ALL of the talkgroups defined along with useful notes like net events and times or a note saying AVOID this talkgoup was very attractive.

GCL Name Contains Contact entries
HSALPHA:   LCL-01; LCL-09; TGIF-31665
HSBETA:   LCL-01; LCL-09; B93-NAmer
RPT1-GSBRC:   LCL-09; B93-NAmer; B3136-NY;
RPT2-GSBRC:   LCL-09; B93-NAmer; B3136-NY;
RPT1-LMRC:   LCL-09; B93-NAmer;
RPT2-LMRC:   LCL-09; B93-NAmer;

You need to put the radio into promiscuous mode as already noted. The talkgroups noted above are not generally busy so they work out fine in this mode and when you are on the HSALPHA hotspot and want to connect to the admin channel on the TGIF network (31665) you just key that in and you're done.
If you look closely at the above you will notice that the repeaters are duplicated while the hotspots are not. The hotspots are simplex and have only one timeslot available. The repeaters are duplex and have both timeslots (TS1 and TS2) available. The Retevis RT73 has dual watch and dual receive capability so we define BOTH timeslots and on the radio we can put TS1 on top and TS2 on the bottom and when we enter promiscuous mode we are listening to everything that is coming in on the repeater on both timeslots. This also means that we dont have to code for and remember on which timeslot a particular talkgroup is available on a given repeater - if TS1 does not work then try TS2.
Wrapping this up
The actual contact list on the radio only contains about a dozen entries. There is no need to define a Group Control list but you could define one and just put all the contacts into it. Is there a downside to this approach? That's still to be determined. I don't use the scanning and roaming between repeaters so these functions may not work well, or at all, with this scheme. As they say, "Your mileage may vary".

'73 KD2WLL