Archive for June 17th, 2012
Here’s a great example of painting yourself into a corner…
Back in the day, I made a voice-only interface that adapted a helmet-mounted electret mic and earbud to an ICOM IC-Z1A HT. A pair of those let us talk companionably as we rode along.
Rule One: Never shout at your wife.
Then I made an interface that combined GPS data (from a Byonics TinyTrak3+ encoder) with the voice audio, all mounted on our Tour Easy recumbents; the interface also supported an external battery for radio power and lived inside a machined case. Eventually, we had two identical radios, interfaces, antennas, and setups on our bikes.
Along comes our daughter, with her shiny-new Technician amateur radio license. I took an early version of the Z1A interface board, force-fitted it into an early version of the machined case that lacked a top, acquired an ICOM W32A HT and another TT3+, did some tweakage, and defined the result as Good Enough. Time passes, she’s promoted to Larval Engineer, goes off to college, and leaves the bike behind (a faired Tour Easy is ill-suited to being left out in the rain and is not a dorm-room-friendly bike).
Knowing that the Z1A on my bike is failing, I get a Wouxun KG-UV3D HT and modify the Z1A interface to match. Then I build an interface PCB for the KG-UV3D, conjure up a nice case (which is why I bought a 3D printer), chop the TT3+ out of the W32A lashup, put everything together, and it’s all good.
Here’s the carcass of the W32A interface in its half-case:
Whereupon our Larval Engineer returns from college and once again needs a radio for her bike. At that point:
- The W32A interface now lacks its TT3+.
- The W32A PCB doesn’t fit in the Z1A case
- The Z1A interface that would fit the W32A radio has the KG-UV3D modifications.
- The Z1A radio has failed completely; it no longer even turns on.
- Get another KG-UV3D, build another interface PCB + case, make it work
- Transplant the TT3+ back to the W32A interface
- Undo the KG-UV3D mods from the Z1A interface, put it on the W32A
Given that she’s going to vanish in another three months, tops, Choice 1 is out. Although the transplant in Choice 2 seems straightforward, it requires tedious soldering and produces an interface in a partial case.
So Choice 3 it is…
The Z1A board with the KG-UV3D modifications started out like this:
Un-modified again and back in its machined case:
Buttoned up and ready to roll:
I put a clamp-on ferrite tumor around the GPS receiver cable to keep RF out of the TT3+, which seems quite sensitive to RFI; the poor thing locked up quite dependably on the bench with 5 W into a long rubber duck antenna, but not into a dummy load. The mobile antenna sits relatively far from the radio on the bike, but I think the TT3+ had problems in the early KG-UV3D lashup.
The TT3 audio level will probably require adjustment, as I’d cranked it up for the KG-UV3D, but that will require some on-the-air testing. Ditto for mic level.
When I get a KG-UV3D for Mary’s bike, I’ll buy two radios and build two interfaces, so as to finally have a working radio + interface on the shelf.
I’m mildly tempted by the new Yaesu VX-8GR, but that’s over $350 for a radio that also requires a new interface board design, a new case design, a new set of adapters, and other odds&ends. Not to mention that the radio’s built-in GPS antenna would live at the bottom of the seat frame beside the wheel and below my shoulder. I suppose I could conjure up an entirely new radio mount, but … the deterrents seem overwhelming.
Various versions of the schematics & PCB layouts for all those boards, plus solid models for the 3D printed case, are scattered here & there on other posts.