µBITX v3 Audio Pop Fix

One of the items on my to-do list with my version 3 µBITX is to reduce the pop when starting transmitting and then again when going back to receive.  Thanks to a ubitx.net page describing a fix to the audio pop issue, my radio can transition from TX to RX without a loud, obnoxious POP.  It turns out that this modification was implemented in the next version of the µBITX (V4).  It basically mutes the audio when the transmit logic line goes high but still allows CW sidetone.

What I like about this solution is that it uses a header mounted on the main board and then a perf board has the updated circuit.  I had a few 8-pin headers so I used two pins to make the anchor to ground which I think will make it more mechanically secure.  I did not have the 1µF capacitor so I used two .47µF in parallel.

I drilled the holes by hand which was surprisingly easy.  The challenging (and aggravating) part was building the circuit paths on the perf board with bits of wire and globs of solder.  But, after a few deep breaths and some muttering, it worked out.

Now all I hear on the transmitter transitions is a couple of relay clicks -- nice and quiet.