[Radioroslyn]

Agreed with previous posts. And if you've dittled with the IF trimmers that will do it too. Always use a generator to adjust the IF stages. You don't need wobbulator. You been reading some old dusty books again. Most of us would know it as a sweep generator. The sets you have been working on only have a single IF amp. You are unable to change the coupling between the coils in side the IF cans( physical spacing) so the bandwidth general is going to stay same. What you can change is the frequency that the IF amp operates. Both IF transformers must be tuned to the same frequency for best performance. The Philco 37-116 and several of the top of the line sets have a knob that moves the coils in the IF cans that change the actual selectivity. Also it has a pot to control the gain of the IF stages so the volume doesn't change as the change the selectivity. Gosh they think of everything!!!!
Terry