W8EMV - Whiskey Eight Echo Mike Victor

Feditalk QSO (DMR, Brandmeister TG 23514) with M0YNG

Proof of work - photo courtesy Christopher M0YNG, showing his newly acquired display screen for his MMDVM hotspot.

This was unplanned! I happened to have the radio on as M0YNG was tuning up. We had a good 10 minutes chat about radios, tech in general, and how hard it can be to find the instructions to do anything technological because of the vast amounts of jargon in use across the board.

dmrconfig - a configuration utility for DMR radios

I have a Radioddity / Baofeng RD-5R DMR radio. I got it back in 2018, and have recently added an MMDVM hotspot for it to my collection.

One of the downsides of programming this particular radio is that CHIRP (which is used to program analog radios) is not available for DMR, and that the supported radio software only runs on Windows. And while Windows is fine, the rig I have to run that at home is an ancient Eee PC with a small screen that makes using the programming software awkward at best.

An alternative to the vendor software is dmrconfig, a configuration utility for DMR radios by Serge KK6ABQ. It supports a pretty good set of DMR radios including my RD-5R, and it runs on MacOS and on Linux. It lets you read and write codeplugs to the radio, and it helpfully converts your codeplug to a human readable file so that you can edit it in a text editor.

So far so good with dmrconfig - I've only used it once, but the programming looks like it took just fine. It's certainly a lot more helpful to have a format that can be backed up easily! It does however make me want to get a radio that can have more user entries in the database, the RD-5R is skimpy on that account.

Also noted but not tried yet: qdmr, which uses the same codebase as dmrconfig for radio codeplug writing but that offers a GUI for it. Worth a test another day.

Thanks to @[email protected] for the reference to dmrconfig - they are using an Anytone 878 radio with this particular setup.

Radioddity RD-5R "RX Group List" - or, why can you hear me and I can't hear you?

A programming quirk of the Radioddity RD-5R.

If you want to add a DMR talkgroup to talk on, there are really four things you need to do:

1. Add a digital contact, listing call ID and name.
2. Add a channel, listing that contact along with frequencies.
3. Add that channel to a zone, allowing you to select it on the radio.
4. Add the channel to the "Rx Group List" so that you can listen to it.

If you miss step 4, you get the following: people can hear you on a channel, but you can't hear them.

Debugging this was tricky. I had added a few extra talkgroups to my hotspot configuration, so I thought I had checked everything - and it turns out I had everything correct for transmitting. What could be different about the Feditalk group? Well, it's UK based, so I tried connecting to the UK Brandmeister server and listening to some other UK talkgroups, and that didn't work.

The AHA moment was of course an RTFM situation. Section 3 of the Radioddity DMR Quick Start Guide referenced a screen I hadn't seen before, the "RX Group List". Adding the channels to that list (and noticing that they weren't there already) fixed the problem.

Thanks to the following for helping me through this bit of troubleshooting:

• Nick W8XM for the ARROW RD-5R codeplug and some timely consulting on RX offset programming
• Patrick KC3OWU for encouragement and debug help and a first successful QSO on Feditalk, TG 23514
• Christopher M0YNG for running mastodon.radio and prompting this exercise in the first place

Having figured all this out, I'm now intrigued by OpenGD77 which is open source firmware for this RD-5R radio and for other DMR radios. Perhaps a next project!

New gear: MMDVM hotspot from Radioddity

New radio! This one is an MMDVM hotspot assembled for and sold by Radioddity. The part I got is clearly labelled "Made in China", but it was shipped promptly from the Radioddity depot in Las Vegas, Nevada. It arrived in a small cardboard box with a single page of tutorial instructions and a few extra screws.

The tutorial text is "Geek Teches THE MMDVM DMR TUTORIAL". I'm certain that it reads better in whatever language it was originally written in, and frankly the text is confusing at best. Fortunately the software and hardware is an ordinary MMDVM and Pi-Star configuration, and there's plenty of good tutorials for that.

Some useful tutorials include:

• Playing with Pi-Star, Amateur Radio Notes, Toshen KE0FHS
• Pi-Star Digital Voice Software, Pi-Star. Official docs
• Pi-Star integration with Brandmeister API, Brandmeister wiki

Nick W8XM was very helpful - I happened to catch him on the ARROW 2m FM repeater while I was putting things together, and I related the problem I had originally where people could hear me but I could not hear their return. It seems that the hardware in this kit is subject to frequency drift, and you need to tune the "RX Offset" with some trial and error (using Parrot) to get an accceptably low BER. At zero offset I had 1.3% error rate; after tuning to -200 my BER was down to 0.2%. Ailunce has a good description of what you need to get to.

I had one glitch on setup - typing in the wrong wifi SSID for our home network! - and had to manually add a new wpa_supplicant.conf file to the SD card to make it work. Fortunately, this tutorial from KE0FHS made that quick work.

The Brandmeister network does not like hear lots of short transmissions in sequence from a single station, so if you are testing things out vigorously and punching a lot of buttons in short sequence you might get a user blocked voice message from the network. This corrected itself for me by waiting an hour.

With all of that set up, I'm back on the air with DMR. There's a weekly Michigan net via Michigan One DMR, and the Brandmeister Feditalk talkgroup is one I hope to make more contacts on.

73 de Ed W8EMV