[R-390] Hook up wire/filters

[Roger Ruszkowski]

Dave,
If the wire will fit and bend it should be good enough.

The original function of the trim caps was to match / set the insertion loss of each filter
so that as you switched from filter to filter the output of the signal would be the same.
We always just adjusted the caps for max on any filter to get all we could get.

You maxed the weak filter and trimmed the others back to match.
Then set the IF gain adjust as needed.

Peak them all.
Set the IF gain adjust in the bandwidth you use most. AM 8 or 16, SSB 4, CW 2.

Roger AI4NI


The #22 solid wire, I've found some silver plated copper wire, actually Silver 
Plated Copper German Bead Wire.  I wonder if that will be satisfactory or should 
I just get plain old #22 tinned soft copper wire.  The price is about the same, 
nominal, I'm only concerned that the bead wire may be brittle.  I also ordered 
some new clear teflon spaghetti.

I'm getting ready to re-install the filters in my IF module. They're all cleaned 
up, and I can't measure any resistance from the coils to ground on any of them.  
I've re-measured all the filters and it appears that the 2K has ~18 dB loss, the 
4K ~23, the 8K ~9 dB, and the 16K ~9 dB which puts them all in spec as far as IL 
goes. Some of them do not meet the variance spec, but I can't do anything about 
that. The 2K is a replacement with a plastic FA type and has about 6 dB variance 
and the 4K had the magnetostrictive wire replaced with 4.5 dB variance, and they 
were both bad/didn't work, so there was no way to know how they originally 
worked.  The 8 and 16K filters were the best with variance, at 3 and 1.8. 
Cleaning up the foam in the 8 and 16 only made a difference with the resistance 
from the coils to ground.

I wonder if I can balance the filters by detuning some with the caps, or will 
that affect the curve?  I haven't tried that on my test setup although I still 
have one hooked up.

No one has responded to my question about filter IL. Is this because it's been 
covered somewhere before, or there just isn't much information there?

Dave
N3DT
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