W8EMV - Whiskey Eight Echo Mike Victor

A reminder to set your password on your MMDVM hotspot

My DMR hotspot was silent for some time because I had neglected to update it with a newly required password.

The Brandmeister network article on hotspot security has the detail that you need to carry this out. You'll want the "hotspot security" section of the "SelfCare" setting at Brandmeister, and on the MMDVM side the menu option is under "Configuration" / "Hotspot Security".

It took but a moment and now all is well again.

Listening to DMR on OpenWebRX

My notes such as they are say that I had OpenWebRX running last year around this time, but the 2019 experience was not accompanied by blogging and I have forgotten what I learned.

This year's install was very simple, using the Debian install instructions and then systemd to start and stop and reload the system.

The 2020 OpenWebRX setup has a lot more digital modes supported, and I was able to successfully decode a transmission from Ralph AA8RK this morning. I was listening on 443.5 (the output frequency of the W8RP DMR repeater) with my setup, which includes a Nooelec RTL-SDR tuner and a 8 GB Raspberry Pi 4. Miraculously, the DMR decoder picked up not just Ralph's voice but also decoded his call sign and channel number.

One funny thing about this repeater setup is that from time to time it will send out a short burst of traffic that OpenWebRX can't decode, see below for that.

New radio notes: Radioddity GD-77

I got two new Radioddity GD-77 radios the other day - one for new ham KE8PFB, and one for myself.

Programming the radio from the keypad is awkward but not impossible, and we got one analog channel up and running to reach the ARROW repeater. That was plenty to confirm that it was working.

We'll tackle DMR next. I have a DMR hotspot, so it should be possible to share it.

The included instructions were in German and in English, and the "how to get a DMR ID" instructions were for Europe. This led to a support ticket - the USA instructions are at RadioID.net.

The GD-77 is supported by dmrconfig, and I was able to convert my RD-5R configuration to it without too much trouble. The GD-77 only has two squelch settings, so the RD-5R's configuration needs to be edited - other than that, surprisingly easy.

The GD-77 user interface is nearly identical to the RD-5R. A few of the key bindings are a little different, but it's otherwise effectively the same radio as far as capabilities and controls. I guess that's OK, but I sort of wanted to get a completely different rig from what I already had. The tradeoff of course is that it was completely familiar.

What is the effective coverage of my DMR hotspot?

My new MMDVM DMR hotspot shipped with a little SMA antenna, and has a power output measured in milliwatts. I wanted to figure out just what kind of effective range I had for it, so that I could get away from my desk while connected to it.

My radio is a DM-5R with low power at 1 watt and high power at 5 watts. At about a block away from home, transmitting on low power, I can get a clear echo reply to my hotspot with Parrot. At four blocks away, the low power TX doesn't get into the hotspot, but my RD-5R still picks up some fraction of activity on an active channel.

The next test was to change to high power (5 watts) on the radio, and to get a better antenna setup for the hotspot. I have a 2 meter ladder line antenna that also works on 440, so I connected that up to the SMA port to see how it would work. My best distance was about 137 meters, as measured by GPS, from my house to the bus stop. That's almost line of sight with just one building in the way using high power (5 watts) on the RD-5R into the hotspot, and Parrot to verify transmissions.

Some other DMR range experiments from Youtube:

• K0LWC measured 0.7 miles (1100 meters) with an Anytone 878 into a 10 milliwatt hotspot, with clear line of sight across a park and no buildings obstructing his view.
• KG4VDZ hooked up a SharkRF OpenSpot 20 milliwatt hotspot to a 50 watt amplifier, and claims a DMR range of 15 miles using a vertical antenna on top of a tower.

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 @witchy@mastodon.radio 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

MichiganONE DMR net

First time on MichiganONE DMR net. Some impressions:

• just because it's digital doesn't mean it's perfect
• state-wide nets get a lot more people! (19)
• some discussion of switch to different time

Thanks to Dustin N8RMA for being net control!

new radio, who dis? DMR day one on a Baofeng/Radioddity RD-5R

Day one on a new DMR radio.

First impressions: when the sound quality is good, it's just fine. No noise, but you do get dropouts. I'm sure that's the quality of the DMR voice encoder/decoder and not specific to my radio.

I have a Baofeng / Radioddity RD-5R, purchased on sale for less than $60. Build quality is fine out of the box.

Programming the radio was the first task. I had previously obtained a DMR ID from RadioID.net so that step was taken care of. The programming software is from Radioddity and runs on Windows only. Helpfully I acquired a little old laptop running Windows 7 so I was able to run it. The code plug I'm using is from W8XM and is distributed via the ARROW club at the Arrow group on groups.io.

Some mysteries to address while they are still mysterious.

Every so often the radio light turns green, presumably because there's a call on the repeater, but I don't hear anything. I'm told there is a "monitor" mode where you open up the radio to listen to this traffic, but I haven't found it yet.

The code plug is programmed for a "Parrot" server, a sort of echo test that lets you check levels and hear the sound of your own voice.

There should be a way to tune in to an arbitrary channel, and this code plug has a slot for "TS2 Custom" which looks like where I'd do that. I haven't sorted out how yet.

I've had conversations on the W8RP.local channel (to W8XM) and on the statewide Michigan channel (to several folks who were helpful in radio testing). In addition I've listened to the TAC310 group which is a bit random but evidently useful.

The radio also supports analog UHF/VHF repeaters in the area and has a broadcast FM receiver just like the Baofeng UV-5R. So you can listen to your favorite broadcast station and then have the radio cut in with traffic.