GPS + Audio Interface for ICOM Z-1A HT

You’ve seen bits & pieces of this in the previous weeks and months: now it’s up and running!

Admittedly, this is brassboard hardware; I must now build three final versions for our bikes incorporating all the tweaks & adjustments. But it’s time to write this stuff down so I can find it again … and perhaps you can use some chunks, too.

What it does:

• adapts the mic & earbud in our bicycle helmets to the mic and speaker jacks on an amateur radio VHF-band HT
• provides a handlebar-mounted push-to-talk button
• transmits the AFSK data burst from a TinyTrak3 GPS interface through the audio stream for APRS tracking
• powers the HT and circuitry from an external battery

Why we need it:

• voice intercom for our family rides: we talk without shouting at each other
• safety communication for public service events supported by the local amateur radio club
• GPS-based APRS position reporting for those events
• trip monitoring on our long solo rides
• it’s a neat tech hack with lots of Quality Shop Time

Major sub-projects (some already partially written up):

• somewhat modified TinyTrak3 board
• circuit board combining voice audio + TT3 + PTT + power
• slide-in enclosure replacing standard HT battery pack
• helmet mic and earbud mounting
• external battery pack
• antenna mount (an easier version) for a standard mobile whip antenna

I don’t have an instruction manual to go along with this, nor is there a parts kit available. You’ll certainly want to modify everything for your own purposes; the circuit board and case certainly won’t fit whatever HT you’re using!

Over the next several days, I’ll be describing & documenting the tricky parts… in no particular order, because I’m not going to sort my notes & photos ahead of time.