[TenTec] Re: DC blocking caps for crystal filters - question

Clark Savage Turner WA3JPG turner@safety.ics.uci.edu
Tue, 30 Jun 1998 19:26:51 -0700

Thanks to all for suggestions and answers.  It was, of course
easy to alculate the impedance of the caps at the IF
frequency of 6.3 MHz, and the 0.1 comes out ahead at .25 ohms,
where the 0.01 would come out at 2.5 ohms.  Not much of a difference,
but what the heck, I had both values lying around, so I went with
the lower loss 0.1 alternative.  

Notice that some filters have matching transformers at the input 
and output (INRAD filters do this) and get a DC path through them, 
wreaking havoc on the little switching diodes on either end.  This
made the blocking caps necessary, and they worked fine.  The INRAD
8 pole CW filters work very well in my Corsair I now, and I will
put them into my OMNI VI and probably let go of my 6 pole (ten tec) 
Network Sciences filters now.

Fun with filters.  Few things finer.


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