Tag: bitx qrp

Adding CW to bitx

Bitx Cw module
Bitx Cw module

I was playing with  my bitx build yesterday. Specifically, I tried to add CW  to the rig.   Original bitx20 is a SSB rig.  I my mod was inspired from PY2OHH bitx40.  I  wired  up a 10mhz crystal oscillator as shown below.

bitx20 CW module

The idea is to inject 10mhz ( approximately) at the  beginning of transmitter IF amplifier. This will in turn produce 14 mhz sine wave at the output.  The receiver part is unmodified.  See the diagram below.  Connect  the point marked X to the point x .

Bitx 20 modified for cw
Bitx 20 modified for cw

Adjust the  10Mhz oscillator to  around 700khz above the  BFO frequency. I added a small inductor (10 micro henry) in series with the crystal to adjust the frequency near BFO,.It is not shown on the figure above.