I recently volunteered doing Amateur Radio support at the Boston Marathon, and was trying to figure out what gear I should bring given that it was going to be my first time and I wanted it to work well. My considerations before the race were mostly around water resistance (or low enough cost where I can take the risk), battery life (ideally charging via USB-C), and fatigue from loud audio in my ear. I also bought a radio harness that was helpful for carrying stuff around all day.

Radio Harnesses

I was a bit skeptical about this one. There’s a survival guide that recommended the “abcGoodefg” one on Amazon, but it was too small. I ultimately ended up getting a used True North Dual Universal Radio Hardness, which was comfortable and had plenty of space.

If I wanted something less expensive and more lightweight I think that a fire radio strap, such as the one made by X-FIRE would work just fine, and I saw a few folks sporting fancier versions of these.

Headsets, Microphones, and Earpieces

I originally thought that I’d probably end up spending most of the time using a Heil Handie Talkie Headset (HTH), but the microphone stopped working about an hour into volunteering. My BTech QHM22 speaker mic saved the day as a microphone, and I used a cheap RLN4941A-type earpiece to be able to hear. It did get loud at times as advertised.

Powering Radios

It was mentioned at the symposium a few weeks before the race that it’s a good idea to make sure you have plenty of battery power on hand. These days, you can get a cheap Baofeng radio and an inexpensive 28Wh battery that you can power via USB-C. That alone is a nice reason to bring one as a backup radio.

Baofeng GT-5R squelch & pop

Next I focused a bit on loud audio. The cheapest radios, such as the Baofeng GT-5R (the compliant version of the UV-5R) don’t protect against surge current when their power amplifiers turn on and off (See Baofeng UV-5: Squelch Pop Suppression), which is annoying at the end of a transmission with a headset, particularly a loud one. I built a cable with some inexpensive diodes to suppress the pop, but it still had an open squelch at the end that was loud.

Squelch Tail Elimination

There are a number of standard ways that you can eliminate squelch tail on an analog transition, with common ones being to use DCS (possibly the best option), CTCSS (PL tone) with reverse burst, and the Chinese radio 55 Hz (or less commonly, such as Anytone, 259.1 Hz) tone. Some amateur radios will turn off the PL tones before they end the transmission as well. There’s some history of CTCSS and some other methods over at Repeater Builder.

I noticed that the repeater for my radio assignment emitted a -180° reverse-burst tone, and this seemed like a good place to start.

Unfortunately, working with reverse burst CTCSS tones isn’t exactly a standard amateur radio feature. My Wouxun radio apparently does honor one at 120°, but doesn’t document this, and I needed -180°. This does seem to be a feature in some DMR radios, including my COTRE CO01D, but I certainly wasn’t going to use a $10 2W toy radio with a fixed antenna and 5.5W battery. My BTech 6X2 and Baofeng GT-5R only work with the fixed tones at the end.

Lucky for me, my TYT MD-390 does work with the right reverse burst, and I was also able to get a large 23Wh battery that charged via USB-C. I used perhaps a third of that battery on race day, and was told I had clear transmissions. But I still had an issue where some transmissions were much louder than others, and I was fiddling with the volume potentiometer a lot of the time. I think what I really wanted was automatic gain control for the audio.

Maybe I should have just bought a Motorola?

Something I did notice was that pretty much every radio in use that wasn’t used by an Amateur, including those that the B.A.A. rented, and the one used by the segment coordinator were made by Motorola. Looking on eBay, the older MotoTRBO radios such as the XPR6550 can be found for pretty reasonable prices, some of them less than $100. I’ve never used Motorola radios before, but figured it would be worth a try for the next time around.

I’ve since bought some, but the process is kind of involved compared to any other radio I’ve had in the past. I talk about it over at Using Motorola TRBO Radios for Amateur Radio.