BITX20 Update #12

I got some more time to keep looking over the receiver of my BITX20 on Tuesday. I fitted a 15 uH RF choke in place of L5 and now I was able to receive USB. I added 15 pF to the trimcap on the 10.000 MHz crystal and got a USB signal that sounded pretty good.

Being now able to understand my voice keyer on my FTDX100 I noticed that no matter where I tuned the three 14 MHz transformers the received audio always seemed weak.

I connected the RF input to my DDS oscillator and, using a home brew RF probe, I measured the output of the 14 MHz RF filter. From here I could see that the 14MHz filter was not tuning to a peak.

I replaced the 47 pF capacitors that I had installed across the filters with 3 X 12 pF in parallel and this enabled me to peak the filer at 14.2 MHz. I have now got some new 33 pF capacitors that I will replace the parallel capacitors with and re-tune the filters.

Now the receiver sounded much louder.

I connected an antenna and listened across the 20m band. I didn’t hear any ham stations but the noise that I hear on my FTDX100 was also heard on my BITX20.

Hopefully this weekend I will get a chance to hear some hams on the 20m band.

Now the receiver is OK I will move on to the transmit section and then the linear amplifier.


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