Dueling 612s  - New Board Crystal Filter Update
Channel: Dave VE3OOI
Date: 2019-05-03

The Dueling 612s new board uses a 12 Mhz crystal filter that was used in the Bitx40.   My prior video shows the bandwidth (as designed for the Bitx) is around 3.5 Khz.

Peter VE3POA found that that changing some of the capacitors in Crystal Filter the bandwidth could be reduced.  

I wrote a program in Java (on my github account) to analyze a 4-pole crystal filter and plot the performance (bode plot).  After a few iterations of changing capacitor values, Peter and I were able to come up with a design that was just over 2 Khz with no more that about 2 or 3 dB of ripple in the passband.   

This video analyzes the performance of the new filter and once again shows how to identify the BFO for USB and LSB.