Super VXo for 3.5 MHz

Every year the QRP-CONTEST-COMMUNITY (qrpcc) institutes the Q R P - M I N I M A L A R T - S E S S I O N (qrp-mas) and  this is the reason I investigated the possibility of a super VXO for 80 m .

These are my resuslt for now.

I used just one BJT as oscillator-vxo/mixer with two different kind of quartz crystals:

- the first one is at 37.850 kHz  3rd overtone (so fundamental frequency is 12.616 kHz)

- the second one is at 27.075 kHz  3rd overtone (so fundamental frequency is 9.025 kHz)

Mixing product should be = 12.616 - 9.025 = 3.591 kHz, but the actual frequency of the output signal is  3.581 kHz (better for me!)

I shifted the two 37 MHz crystal in a "superVXO manner", and obtained a final VXO-frequency-range of: 3.581-3.561 kHz very good for CW portion of 80 m band!

                              The schematic is here (clik to enlarge):        

Frequency stabilty is enough for CW operations. I measured at the top and bottom band edge using Spectran software to monitor the

signal from  an FT817 trough the sound card;

 these are the results (the program was at QRSS setup):

                          3.561 kHz measure                                                                               3.581 kHz measure

Yes, I know it's not a really minimal schematic, but for me it was the reason to use the solder doing a new little toy for my

 hobby!...   :)