[R-390] Q IF And Audio Module Tube Optimizing

[Tisha Hayes]

With the bandwidth switch set to 2 KHz someone may want to explore how
linear the frequency response is. It would be interesting to see a curve at
1000 Hz in addition to the 400 Hz test.

In fact, we may want to add a test step to go through and peak the trimmer
capacitors on the mechanical filters (if they are there). I did not check
all of the steps in the multiple postings but if we have not do a test of
individual filter performance we should add steps for that as well.

It is disconcerting to me to be trying to dial into a signal and when I
rotate the bandwidth switch I hit spots where the signal just completely
disappears. I have some examples were it was not just related to the S/N
ratio and a wider bandwidth resulting in an AGC action that drives the
desired signal down through the floor.

I have seen this issue appear in some very high end receivers where there
are no means of trimming a newly installed filter. Some of us know about the
trimmer caps that were added as a later mod on the R-390A. Do you know that
a receiver like the RF-590 from Harris does not have the ability for you to
trim that capacitance if you add or move filters around?
-- 
Ms. Tisha Hayes/ AA4HA
-
Optimist: *The glass is half full.*
Pessimist: *The glass is half empty.*
Engineer: *The glass is not sized correctly AND we need a backup system.*