Changing the capacitance at C102/C103 will adjust the frequecy of the BFO, , typically at 11.998500 mhz.
Farhan found that with 47pf at C102 and with all five 12mhz crystals matched, the BFO was placed correctly with respect to the crystal filter for LSB use.
There are reports that some get better audio if the frequency of the BFO is adjusted a few hundred hz from that point.
However, the value that worked for Peter may not be the value you need on your rig.
If you wish to vary the BFO frequency for better audio, I suggest you change out C102 and add a trimmer capacitor at C103.
The 47pf Farhan settled should be within the range of C102+C103, your setting for best audio might be above or below Farhan's 47pf value.
For example, perhaps remove C102 and put a 100pf trimmer at C103.
Or put a 20pf cap at C102 and a 50pf trimmer at C103.
A better solution would be to drive the BFO from CLK0 of the Si5351 as is done on the uBitx,
then we could add code to the sketch to adjust the BFO frequency from the calibration routine.?
Jerry, KE7ER
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On Sun, Jun 11, 2017 at 02:35 pm, EA3IAV wrote:
I have noticed that when intouched with the tester probe into the the sound from the speaker become louder.
So, i decided to try this mod that Peter showed o his video
?
