BITX20 Update #10

It works ! Well, as much as I have tested anyway.

I finished placing the 0.1uF ceramic capacitors and added a reverse polarity protection diode and a 12 Volt power cable. The protection diode is just in case I make a mistake and get my wires crossed.

I wound the inductor, L4, on the spare dumbbell former that Sunil had included with the kit. I am not sure how many turns I put on it but, like the transformers, I was using 0.3mm diameter wire. I think there is 20 turns, 10 up and 10 back.

I connected my Altronics frequency counter to the emitter of Q6 via a 0.1uF ceramic and turned the power on. Nothing. No signal at all.

I grabbed for the multimeter and measured the DC coming into the board. Nothing. I checked the in-line fuse. Nothing. That was the problem. No fuse.

I put a fuse in and then I got about 4.6 MHz signal from the VFO. I added the 60 Р160 pF tuning  capacitor and got a tuning range from about 4.03 MHz to 4.55 MHz. The frequency was moving around as the circuit warmed up but after about 15 minutes it seemed to stabilise quite a bit. I listened to the oscillator on my FTDX100 and it sounded clean but the drift was noticeable.

Hopefully once I box the board up the drift will be less as it seemed to really matter where I put my hands and body.

Tomorrow night I will wind the L5 inductor for the crystal BFO oscillator and get that going as well. After that I will connect RX and TX power and then tune the 14 MHz filters and, all going well, everything else should work.


This entry was posted in BITX20. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *