Re: Tuner alignment procedure causing thermal drift


EJP
 

The problem was in the alignment of the discriminator coil T2. At 98MHz I was using the 400Hz modulated IF pattern on the o'scope to set the tuner to center frequency ...

Stop right there. You have two moving targets here, not just one. 
You should inject 10.7MHz swept +/-150KHz or more into the IF strip, or even very close to the discriminator if it's separate, and adjust the top coil to centre the S curve on 10.7, and the bottom coil for maximum height and slope, and then minimum distortion of a sine wave if you like. You're trying to pull yourself up by the bootstraps the way you're doing it.

EJP

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