Quote:
Originally Posted by crackle
I was wondering if someone could please explain more about changing the value of R2. Is this recommended change to reduce the extra output from Q1 or is it to help boost the level from Q1, I didn't quite understand it.
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I was wondering if anyone could please make any comments to help me understand why this was changed to 2.2k.
I substituted a trimmer in place of R2 and found the best performance was when it was set to 5k.
I can also confirm that my issue with frequency drift (it was over 2kHz) was caused by the RF inductors supplied by Spectrum communications some time, they must have supplied me from a duff batch.
I have reverted back to using an inductor taken from an old transistor radio, (yellow colour ferrite, full width, not the tiny slug type.)
To assist in setting the frequency I have added a very tiny trimmer, probably less than 20pf. This gives a finer adjustment. With this combination the frequency drift, over a 2 hour period, is now less than 400 Hz either side of the set frequency.
Mike