Saturday, February 04, 2023

My terrible build of the Soldersmoke DC receiver

Bill Meara of the wonderful Soldersmoke blog and podcast, recently published a nice design for a direct conversion receiver. He was looking for people to build it as described to check that the design was reproducible. I'm sorry to say I diverged in a few ways:

  • Used a TUF-1 mixer
  • Used an LM386 audio amplifier
I've done all sorts of things wrong, leads are too long, I didn't have any temperature stable (NPO) capacitors so the VFO drifts terribly.

My lame excuse is a poorly stocked junk box.

It needs to be boxed up and shielded but it is now working and with care I can listen to stations on 40m sideband quite nicely.

This morning I watched Bill's video of his version and spotted a ground strap to the nut in the PTO. I thought that might have solved all my problems! I think it helps but it's certainly a good idea to reduce the effect on tuning of a hand being near by.

Not good but it's satisfying to build something and use it to do ham radio. This is just a start. I can certainly recommend a direct conversion receiver project for anyone who longs for the joy of oscillation.


I didn't have a 9.1V zener so had substituted a 6V three terminal regulator with two diodes on the earth pin. There was oscillation which I had reduced with bypass capacitors but still the waveform was a bit fuzzy on the peaks. Today some Zeners arrived so the regulator is gone. The VFO signal now looks excellent.

Temperature stability is poor and my hand affects the frequency. Paul, VK3HN, kind of predicted this. Still a fun project.

1 comment:

Bill Meara said...

Excellent Peter! A great start! Now, just build the AF amp and the diode ring and you will officially be inducted into the SS DC RX Builders Club! Seriously, I think is already sounds pretty good. 73 Bill