Re: Starting Over

KC8WBK
 

I have 3 BITX40's.  The first one had loose toroids flopping about and it worked for a while but I tried to tighten up the toroids and it changed something and I no longer could tune the analog VFO to 40 meters, so I bought a second board with one of those newfangled Raduinos.  That board had a broken toroid wire, which I fixed.  I got that one working but did a few mods to it, changing resistors for less drift and due to poor soldering work had variable audio output.  I then ordered another board and a Raduino for the first board.

I got board 1 to work with the Raduino and installed it in a case and it seems to work well after I went through and tapped all of the solder joints that I had worked on and found one cold joint that made noise as I gently tapped the resistor.  With a little heat on the solder joint, board 1 was working well in its case.

I got board 3 to work but had intermittent problems related to my case and installation, later I found a solder blob grounding the speaker to the case, which was also grounded to the antenna.  So after removing the blob, things worked much better.   I also did the 13.8V power supply thing and was lucky enough to shut down the radio before any damage was done.  I installed a really nice PTT switch out of my junk box on the board 3 case, oops, it was a normally on button which caused me to blow the IRF510.  After installing a new PTT switch and replacing the IRF510, board 3 works great.

I built a BITX40 repair station which is a piece of wood with Raduino, pots, speaker and connectors set up to allow me to work on a board.  It has a 12V power take off so I can use it to build an AGC and experiment with 20m bandpass and lowpass filters.  It is set up so that I can take any of my boards and mount it and have easy access for testing probes, or working on the board.  I installed board 2 on the repair station and it seems to be working OK now.  I will soon be modifying it so who knows how long it will be working.

I think that if you have a good case and good solder joints on your connections, the BITX40 can be a reliable radio, as long as you don't take it apart a lot and change things.  Most of the problems that I had were related to poor building techniques, which caused me to learn how to do better. 

I really like that case, I think it will make for a much more reliable radio.  A lot of the problems I had were related to poor self-built case design, not enough clearance, forcing connectors, squeezing the Raduino in and out.  A ready made case solves a lot of problems.  I may need another radio to build one of those, it would make a nice mobile rig.

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