Frank and Perry were on 85 talking about vintage receivers and their IF adjustments, bandwidth, and filter shape. One very useful tool when fooling with the old gear is a cheap SDR receiver. I have a few, I really like the sdr-iq from RF space, no longer made but around, very well made, metal case, good design. You can hook it up to the IF on a vintage receiver and SEE the filter shape. In the old days they had sweep generators or wobulators which were rare and hams used more guesswork then anything else. I have an IF tap on the homebrew receivers off the last IF, just a 3pf cap. That gives a nice scope output, plus allows me to see the IF shape. That is homebrew RX number 2, just band noise. Quite a good filter shape from the Kiwa filter after the mixer. That is the narrow filter switched in, its only 1Kc less. That is homebrew number 1, I can see it needs an adjustment of the IF cans to correct the filter tilt. Adjusting things like trimmers and the IF cans, you can SEE the filter shape and also see more or less signal strength as things are peaked. You can stagger the IF cans to broaden the response, or peak things up to be narrow. This is very fun to play with.