W8EMV - Whiskey Eight Echo Mike Victor

Tuning an MMDVM hotspot to minimize BER for multiple radios

My RD-5R gives about 0.4% BER when talking to my MMDVM hotspot, but my GD-77 with the same configuration gives nearly 1.0% BER. Audio quality is still good, but of course it's worthwhile to tune things to minimum error rates regardless.

Some notes on tuning the TX level on the radio:

• N6AMD, How to tune your MMDVM repeater with an SDR for low BER. Focuses on getting your audio levels correct; "If the raw audio is either too quiet or too loud, subscriber radios will not decode the digital signal properly." Uses pistar-mmdvmcal and an SDR to calibrate audio levels (TXlevel).

• F5UII, Install MMDVMHost on Raspberry Pi and tuning MMDVM for DMR digital mode . N6AMD's article is derived from this one, which uses both SDR and oscilloscopes for tuning. "The goal is simply that the audio levels are not too strong and do not saturate the analog input of the arduino".

Some notes on tuning the RX offset on the hotspot

• Ailunce, How to set RX TX offset. "Also every DMR radios may get a different BER when using the same hotspot. If you can't find a good balance for the BER between the different modes, it may be better to use different hotspots for each different mode."

Thanks to Christopher M0YNG on Feditalk to help me with some tuning ideas.

2020 software defined baseball season

Previously: 2019 and 2018.

The goal is to enjoy as much of the pandemic-shortened 2020 baseball season as I can via listening to far-away AM stations through SDR receivers.

I'm continuing to use the baseball section of my commonplace book to keep track of who's broadcasting where, and where you can listen to KiwiSDR or WebSDR receivers to tune in those broadcasts.

Two big changes in my listening since last year.

For East Coast stations, I'm more and more relying on listening through the WebSDR at K3FEF in Northeast Pennsylvania. WebSDR's can readily handle 50 or more simultaneous listeners, so there's less chance of congestion. This particular listening post will pick up stations from Connecticut to Washington DC.

In the KiwiSDR world, there are more and more Kiwi's that are using advanced technology to squeeze out more listening channels than the typical 4 channel setup. N6GN in Fort Collins runs a Beaglebone AI KiwiSDR setup that offers 14 simultaneous users. The usual tradeoff is that you get less of a spectrum waterfall display and more audio channels.

Some teams are easier to follow than others. I don't have a good way to copy Padres games, except via their Spanish language station. Phillies daytime games can be picked up via a station in Scranton, but 2000 watt WEJL drops down to 32 watts at night, not much of a powerhouse. Receivers do wink in and out from time to time, so any given listening suggestion is not a guarantee.

It's weird to listen to games, knowing that the crowd noise is synthetic, and knowing that some teams like the Marlins have had a piece of their season wiped out due to COVID-19. But it's still baseball - a weird, slightly mutant baseball, with seven inning doubleheader games and men on base to start extra innings.

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.

Operating notes: new net protocol for Washtenaw ARPSC net

Our ARPSC (Skywarn) net switched to a new check-in protocol on the Sunday night net. Rather than giving your entire info all in one go, you check in with just a call sign, and then net control calls a roster.

This makes the net more of a directed net, and spends less time on calls that double. It also means that net control has more than one opportunity to correct a missed call sign.

Never one to miss an opportunity to innovate, I'm going to try this approach on a big zoom call, one where it's always uncertain who goes next.

See https://mastodon.radio/@w8emv/104703215788181316 for discussion.

Fine business! Moving to Twitter handle @W8EMV

I'm switching around my Twitter setup so that my main account is now @W8EMV. The goal is for everything in that stream to be on topic, with two acceptable topics of radio (ham radio, shortwave and AM DX listening, SDRs, whatever) and work (open source ecosystem development at Packet, an Equinix company).

With any luck the narrowing of focus will result in a more manageable stream. Every post should include the word "radio" or "open source" in some measure, or reference the same.

My old account still exists but it's protected. As the Green Bay Packers once said, "Fresh Start with Bart". It was too much work to even comprehend how to deal with 60,000+ tweets.

Twitter is problematic for many reasons, so I'm trying to only reopen a narrow channel to it.