[R-390] Mechanical filter Alignment

[Roger Ruszkowski]

Gordon,
 
In the beginning there was no adjustment.
Some nice values were engineered and the
best cap values were installed.

The first production runs from Collins did not 
have trim caps. A fixed value was used.

If you have one of these early decks be happy.
You have one of the  original early IF deck modules.

Look on the IF deck side of your receiver frame.
Do you have a set of 4 holes in the side that lets you 
look at the IF deck where the trim caps under the
IF deck could be adjusted? 

You hope not. So you also know if you 
have an old early frame (not holes) or
a later production frame with holes.

A lot of adjustable IF decks went into frames
with no side holes. You tilted the deck out to do 
the trim cap adjustment. Then late model frames
had holes added. Look out for hand drilled frames.
Not a problem but you know its a post production change.
 
Some one though service people did not have enough
to do and decided that caps to diddle were needed.
So trim caps were added. 
 
If your IF deck does not have them, then be blessed
and leave it alone. It is good as it gets. 
 
You just can not add them in.
They are not needed.
 
Besides the caps do not align the filters at all.
They just get a bit better or not better impedance
match in and out of the filter for more of less
signal level passed through the filter.
 
The Idea was not to align the filter.
The idea was to adjust the four filters for the
same relative power level. And this was not
necessarily the maximum power through any of
the filters.
 
Roger AI4NI