Re: BITX in Texas

Allison Parent <kb1gmx@...>


Some comments inserted in line.

--- In BITX20@..., "Dave WardenDurkee" <dwarden2@c...> wrote:

Hi Jim,
I live in Leander, Texas.
I've built one BITX 20 (20 Meter band) so far using all through hole
I used a PCB and I never finished the transmitter because of a spur
in the output that is at 12Mhz.
One of the things to watch for is tuning to the third harmonic of the
VFO or the mixer having bad balance(excessive VFO feedthrough). Insure
the bandpass filter is really tuned to 14mhz as it's easy to tune
low and get excessive 12mhz output. I found making the Mixer doubly
balanced and matching the diodes for forward voltage at 2ma gave
improvement. Also watch the L-C ratio of the bandpass filter if you
deveate from the published values excessively the filter will have
very wide skirts and the output will have too much 12mhz and possibly
10mhz. Like all filters layout is important.


I redesigned some of the circuits and a new PCB using about half surface
mount parts. I hope to get a cleaner signal with my second BITX.

How far are you into building the BITX?


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