Tune frequency of an oscillator

[Aleks]

HI all.

I'm building an SSB transceiver with an IF of 9MHz. I have the crystal filter centered on 9MHz with a bandwidth of 2.7kHz. The BFO has a crystal of 8998.5 kHz but it oscillates on 8996.4 kHz and the sound is distorted when I receive a signal. The BFO frequency needs to be 8998.5 kHz constant in order for the crystal filter to give the USB signal only.

My question is, how can I fine tune the BFO in the magnitude of several kHz in order to get 8998.5 kHz output.

Here is the circuit that I'm using for the BFO :

**broken link removed**

 

[MikeMl]

Depends on the rated capacitance of X1. Most crystals build for parallel-mode oscillator (which this is) are designed for a load capacitance of 32pF. Your oscillator loads the crystal with about 80pF, which lowers the frequency by about 2kHz. Replace the 150pF capacitors with about 75pF and try it again. You can make the lower capacitor a 10 to 50pF trimmer to tweak it on...

 

[Aleks]

Thank you MikeMl, I will try that

 

[flat5]

Good luck with your project!
If you would like to show us your progress from time to time (in the project sub-forum) I would be interested.

 

[Aleks]

Good luck with your project!
If you would like to show us your progress from time to time (in the project sub-forum) I would be interested.

Sure, no problem, I will try to make a post later today

All the best

 

[Diver300]

You could try leaving the existing capacitors alone and adding a trimmer capacitor in series with the crystal.