u94

A stereo/binaural tactical headset

One thing I hate doing when I’m taking down notes at a radio comms event is juggling a hand-microphone and pen/paper/tablet/computer simultaneously. So I tend to prefer a headset for my radios rather than a hand-microphone. Some models (especially Kenwood) have lots of selections available, but some are very much restricted. In particular, I prefer a binaural headset as I find it more difficult to hear a voice on one side than via both sides — particularly in noisy conditions. The only options I could find for Yaesu/Alinco sets were big chunky earmuff headsets — great in those noisy situations, but not so great if you need situational awareness.

The plan thus is to cobble together my own binaural tactical headset. Stereo using my standard headset connection, so I can re-use it elsewhere.

I did have a Kenwood TH-D72A — a good solid performer… but sadly no longer manufactured (neither is its successor, not that Kenwood ever sold that here), and my particular specimen now refuses to have anything to do with the internal battery. I bought an Alinco DJ-G7T as a back-up hand-held for pure voice comms, and more recently a Yaesu FT5DR. I had made my own Kenwood headset adaptor to use with my headsets, but I had nothing equivalent for the Alinco or Yaesu sets.

As it happens, the headset pin-out of the Alinco is nearly identical to that of the earlier Yaesu VX-6/VX-7: 3.5mm threaded TRRS. Both radios put the speaker on the tip, microphone+PTT (in series) on the sleeve-most ring and 0V on the sleeve. Alinco use the tip-most ring for a 3.3V rail, whereas Yaesu use this same ring for a data/clone connection. Maybe it’s a UART which “idles” at 3.3V on Yaesu rigs, but I wouldn’t bet on all Yaesu accessories working on Alinco and vice-versa — however headsets rarely need a 3.3V rail. (Maybe the VOX ones do… not sure.)

The FT5DR is actually compatible with the earlier VX-6/VX-7, however the connector is on the side of the radio, and while the threaded 3.5mm connectors fit, they stick out the side like a sore thumb: a right-angled 3.5mm TRRS is a better “fit”.

Luckily, Amazon have quite a few options that convert these radios to a U94 “Nexus” military-style connector. I managed to pick up a U94 adaptor that works quite well with the Alinco, and does work with the Yaesu (although is mechanically not optimal due to the “straight” style of the plug and side-mounting of the socket).

Tactical headsets come in a few varieties:

  • ear-tube covert-style headsets
  • D-loop style
  • throat-mic headsets
  • “bowman”-style headband headsets
  • earmuff-style headsets
  • motorcycle headsets

The only ones of this list that are binaural out-of-the-box are the earmuff headsets and the motorcycle headsets. I figured I’d pick up a couple of cheap “bowman”-style ones and see if I can cobble two mono headsets into one stereo set. I looked around, and bought two of these.

The adaptor turned up a week or so ago, and the headsets turned up today. There’s two different varieties of pin-out for the U94 connector — the “NATO” standard interleaves the speaker and microphone pins, whereas the “civilian” standard puts the speaker on the sleeve/sleeve-most ring and microphone on the tip-most ring/tip. Both adaptor and headset turned out to be “civilian” standard, so the first hurdle was cleared.

I tested both headsets and confirmed they both worked. I tried the headsets both with voice comms, then tried tuning to a local FM broadcast station to assess audio quality. They work, but audio quality is not what I’d call wonderful. Very tinny, fine for voice comms, but maybe telephone quality at best. Ookay, so using these as a stereo headset can be done — but if I wanted to use them for anything but straight voice comms, I’d want to swap the speakers out for something decent. Tear-down time!

I picked a “victim” and attempted to disassemble it. These units appear to be glued together, so you wind up partially destroying them to get at the speaker:

The speaker is a conventional 8ohm 500mW jobbie, nothing remarkable… and a frequency response that’s truly awful for anything other than voice comms. Fine for the intended task, but as I say, not really sufficient for what I was after.

I’ll see if I can swap this speaker out with one liberated from some headphones and see about replacing the strip of plastic I had to unceremoniously and destructively rip out — this shouldn’t be a difficult job. The other thing that might help is some sound-damping material behind the speaker, which might account for some tinniness.

If I get this headset working acceptably, I’ll do the same mod to the other, then can look at wiring the two together into a stereo set using a DIN-5 matching my other headsets. I can then re-purpose the U94 plug to make an adaptor to convert my other headsets to use with the U94 adaptors.