[Collins] testing 51J4 filters?

jeremy-ca km1h at jeremy.mv.com
Wed Nov 14 21:34:03 EST 2007


Mechanical filters are usually 5K input and output impedence. A 50 Ohm 
generator will load the input down possibly to the point of no or extremely 
low signal transfer. Raising the generator level too high can ruin the 
filter elements.

One way around it is to wind 2 toroid baluns to do the step up in 2 stages. 
The same for the output if the scope is also 50 Ohms, just hook them in 
reverse. If the scope is high impedence than terminate the filter in 5K.
The center frequency is 500 KHz and I believe they are bi directional but 
not positive; Ive never needed to test my J4.

Insertion loss is around 10-12 dB.

Carl
KM1H






----- Original Message ----- 
From: <eugene at hertzmail.com>
To: <collins at mailman.qth.net>
Sent: Wednesday, November 14, 2007 8:41 PM
Subject: [Collins] testing 51J4 filters?


Hello all,

Finally found a 6.0kHz mech filter for my 51J4 (also got a 1.4 too).
Problem is, my 51J4 is inoperative presently. I was wondering if there
are some simple tests I could perform on these filters that might tell
me either they work, or are likely to work? Or perhaps that they are
dead? Test equipment available includes rf generator, scope, hp410B
meter. Are there some simple tests I could perform?

Thanks
Eugene w2hx

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