[R-390] Staggertuned IF Question

[Flowertime01 at wmconnect.com]

 seem to remember that the first run of R-390A (the ones WITHOUT the 
trimmers on the top of the mechanical IF Filters. The Mechanical filter 
cover does not have a dimple at the mounting screw) was straght tuned. 
When Collins did the mod to add the trimmers, they also changed the 
circuits on the IF Transformers to stagger-tune them. At least that is 
what I remember from the R-390A classes.

---------------------------
Mark,

I think you are right on the Collins Radios.

Then later non Collins manufactures went back to the straight 455 tuned IF 
strips.
The transformer and cap values in the cans were changed to get enough 
bandwidth and can so that a straight tune was wider than the mechanical filters.

As most of the receivers were not Collins receivers most of the R390/A are 
straight tuned.

We tuned every thing straight. Remember I was tuning for a bunch of CW 
operators and they could have cared less about any thing more than 2K wide.

If you are trying to tune the IF for some good Short Wave AM reception, then 
getting the sweep generator out and doing the adjustment with a visual pattern 
on the scope is the way to go.

Try stagger tuning your IF deck and it will not take you long to determine if 
it is a stagger tuned deck or not. 

More bandwidth is more fidelity. It is also more noise in the band pass. If 
you are doing DX SW a narrow bandpass may still be a better option. You can get 
a lot more fidelity by recapping the AF deck up to a good 16KHz audio than 
you realize by opening up the IF bandpass. Until you get the Audio deck to 
respond to 16KHz there is little point in trying to tune an IF deck out to that 
response width.

Roger. AI4NI