[R-390] Trim Caps Science Experiment.

[Flowertime01 at wmconnect.com]

Fellows,

I do not have a sweep generator and would like someone to conduct a science 
experiment for us using said test equipment.

Selecting an IF deck with filter trim caps. Applying the sweep generator to 
the IF at 455Khz plus and minus 16 Khz. Monitoring the output of the IF deck 
with suitable scope to go with sweep generator.

While sweeping a mechanical filter and observing the output band pass, slowly 
vary the trim caps. Repeat this procedure for each mechanical filter and 
adjust both top and bottom cap for each filter.

While a test conducted on one item is a statistic of zero value would you 
attempt to report your observations on the following.

Does the filter band skirts change in width with changes in cap setting?
Does the filter bandpass shift in center frequency with changes in cap 
setting?
Does the filter become more peaked with changes in cap setting?

If the filters do not shift frequency or bandpass width, then any other 
change in filter response from adjusting the trimmer caps can be "faked" by making 
other adjustments else where (IF gain adjust) in the receiver. Thus rendering 
the trim caps nice things to have and diddle with but not required to make the 
minimum passing receiver.

Thanks for taking on the project and reporting your results. Just what do 
them caps really do for us?

Roger AI4NI