I don’t always play radio with a laptop. Still, when I do, I love my Elecraft KX3 and micro KEYER III from microHAM for running a portable amateur radio station in the field or from the comfort of the house. It’s a fantastic setup and makes it a joy to operate. But I am not fond of its DB37 jack and the octopus cable you must build to connect it to the KX3. Even with a rig supported by microHAM with a custom cable, you still need to spend another 100 Euros. Also, it’s a complicated setup to build and a pain to modify or repair when something is off in the cable. And last weekend, I set out to fix this. Given that this is meant to be moved and used, I don’t want bespoke things if I can avoid them.

Last weekend, I fired up KiCad and whipped out this adapter board below. It is compact (~70mm x 31mm; and for you in North America, it’s 2 3/4 bananas wide and just a little more than a banana deep) and uses standard 3.5mm jacks with run-of-the-mill male-to-male cables to connect to the KX3, PX3, and KXPA100 (depending on the day’s setup’s needs). And it’s shallow enough that CI-V, PS/2, iLINK, and PADDLES jacks are not obscured above the DB37 or any of the connectors on either side.

I’ve published the design on GitHub for anyone to go and look at eCAD files. You can order the board (well, three) from OSH Park for $17.50. All parts are passive and through-hole and trivial to solder.

Here is the complete BOM:

ManufacturerDescriptionMPNQuantityUnit PriceExt Price
TEDB37 female5747847-61$9.01$9.01
Phoenix ContactTwo-position, spring connector19897481$0.40$0.40
Tensility3.5mm TRS jack54-002995$1.17$5.85
Tensility3.5mm TRRS jack54-001761$0.91$0.91
BOM pricing from Digi-Key as of February 27, 2023

All you need to do is add your shielded 3.5mm TRS (5) and TRRS (1) cables to the mix, and you’re done.

Four cables go to the KX3 (ACC1, KEY, MIC, PHONES), and two cables are for an external PTT switch (hand or foot switch) and a set of headphones.

You can plug this board directly into the micro KEYER III or use a standard, straight-through male-to-male D-Sub DB37 cable to give yourself more room and pot the board and connectors into a chassis. If you want to go panel mount, skip the Tensility jacks, buy whatever you want, and solder the cables to the board.

Leave a comment below on what you think about this. Hopefully, this is helpful for somebody else. Why hasn’t anyone else done this before?

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