Radios with the same integrated circuit but with different FM selectivity

Ylli said:

[This should have posted yesterday but obviously I forgot to click on the "Post Reply" button. ]

AFC tends to lock a receiver on a strong signal and hold it there even as you tune slightly off of frequency. So it is quite possible the AFC is holding your receiver on the stronger signal as you tune over the weaker one.

There is a slight difference between the two receivers in the AFC implementation. One couples the AFC tuning diode to the FM oscillator tank with a 1 pF cap, and the other couples it to the tank with a 2 pF cap. Could be enough to make the difference you are seeing.

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