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.

73

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