[Collins] wider audio for 51J4?

[kirklandb at sympatico.ca]

j-4 still has 2 stages of IF selectivity after the mechanical
filter. the j-4 is a j-3 with the 1st IF transformer replaced
with the mechanical filter kit.

Several folks have indicated that lab based j-4's didn't use a
6 KHz mechanical filter, they used some form of capacitor coupled
network. I don't have a schematic for this but would greatly
appreciate one.  Conceivably one could make up their own
tuned circuit to use in place of the 6 KHz filter.  Anyone
know the terminating impedances for the mechanical filters??

If you want to open up the BW even more then you would need
to change the coupling caps in the IF transformers as well.
This was done in certain j-2's.

You are not the first to ask for dead mechanical filters.
I've asked previouly to no avail.

Bill, Ve3jhu

> 
> From: "Eugene Hertz" <ehertz at tcaf.org>
> Date: 2006/06/13 Tue AM 10:25:32 EST
> To: collins at mailman.qth.net
> Subject: [Collins] wider audio for 51J4?
> 
> Hello all,
> 
> In a discussion with a friend, we were talking about the narrow 6kc filter of the 51J4 and we were wondering can this be replaced with some simple rc filter (or otherwise) for better AM audio bandwidth?  Can 12kc be attained? Whats the most (at the sacrifice of selectivity)?
> 
> Anyone have (or can point me to) a circuit diagram for a nice wide output?
> 
> thanks!
> Eugene
> PS Someone out there in collins land must have some bad J4 filters,no?
> 
> 
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