[R-390] 4kc filter repair?

Tue, 13 Apr 2004 03:02:22 -0400

Curry has filter products already for the 390a.
http://www.r390a.com/html/Curry.html

----- Original Message ----- 
From: <[email protected]>
To: <[email protected]>
Sent: Monday, April 12, 2004 9:22 PM
Subject: Re: [R-390] 4kc filter repair?

> A good subject on ways to rebuild or re-work the mechanical filters used
in
> the R-390A. My current thinking is to look into the new Rockwell/Collins
> mechanical torsional filters and adapt them for use in the R-390A, along
the lines
> of what Curry Longwave Products are doing. The new Rockwell/Collins
mechanical
> filters are small enough to fit inside a 3/4" diameter metal tube that
could
> be cut to similar dimensions of  the original filters for mounting inside
the
> filter box cover. They currently list symmetrical filters in 3.80KHz
bandwidth
> that would be close to the original 4KHz wide units. The newer filters
have a
> much lower input and output Z of 2K ohms so a matching network will need
to be
> mounted on the input and output sides for step-down and step-up to the
HI-Z
> used in the R-390A circuits. The whole thing could be mounted on a circuit
card
> small enough to slip inside a 3/4" diameter metal tube with end plugs. I
> wonder if anybody has looked inside one of the Curry filters to see what
kind of
> matching network was used? Might be a fun project to try to produce a line
of
> replacement filters for the R-390A. 73 Todd Roberts WD4NGG.
>
>
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