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Hi Bob,
The manual for the Admiral 20A1 was very helpful. In the description of the RF section there is mention of a trap for "adjacent channel picture rejection." There are also several caps for alignment and setting a bandwidth. You are right. The tuner bandwidth is adjusted for one channel. The full skirt of the tuner RF response curve in Figure 32 (page 15) is over 10 MHz wide, but the tuner 3 db down points are about 6 MHz apart. The station channels are 6 MHz apart. This is all designed tighter than I thought.
I saw the tuner alignment test point(labeled W). This is the grid leak circuit you mentioned. Why isn't this RF, instead of the passband response voltage shown? This point must be detected to get the response curve, no?
Steve
W is near the middle of the picture.
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