Hi all,?
I found a simple fix for my receive noise. I used an antenna tuner!
Thanks for all the good suggestions from the group.
As well as changing my Bitx40 enclosure, I had changed my antenna. I went from a 40m dipole (with a balun and coax feeder) to a ZS6BKW with parallel feedline, a balun and coax into the Bitx40.
I presume the feeder picked up more noise and my Bitx40 front end was being swamped. I guess the MFJ-901b tuner has improved attentuation of the out-of-band signals.
Now receive is good and I¡¯m getting about 4 watts out from 12v and 10w out from 20v (measured on a Daiwa CN-801HP).
73s
John, VK2VOL
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Hi all,
I moved my Bitx40 board to a smaller enclosure and somewhere along the line I ended up with massive breakthrough from AM stations.
This happened even with the VFO unplugged from the board.
The breakthrough stopped (surprisingly) when I grounded the centre contact of the antenna input. 7mhz ?SSB signals came through fine!
I experimented with a couple of capacitors across the antenna input instead of the grounding, and finally used a 100pf capacitor.
Now the receive is great, no AM breakthrough at all and a reduction in noise. Signals still getting through fine.
Transmit seems ok (on a nearby receiver), but I haven¡¯t tested power output.
I¡¯m not sure how that all worked. I have Peter parker¡¯s improved audio transmit mod. Also?removed the 1uf capacitor between pins 1 and 8 of the LM386
and replaced with resistor/capacitor.
Any thoughts?
John
VK2VOL
