75S-1 CW Filter Suggestions

John Kolb jlkolb at JLKOLB.CTS.COM
Thu Sep 20 01:03:16 EDT 2007

At 10:38 AM 9/19/2007, Glen Zook wrote:
>--- Steve <stever2k at MCHSI.COM> wrote:
>Does anyone know what CW filters will work in a
>Collins 75S-1?  Will any Mechanical Filter designed
>for 455 KHZ work  as long as it can be mounted? Is the
>center freq of the filter exactly 455 Khz?  I picked
>up a very nice 75S-1 and it has no CW filter in and I
>miss not having one and thought I might try and find
>something suitable that will work..
>Does the filter have to be a Mechanical filter in
>order to have the right input and output impedances or
>could I possibly use a crystal filter with the right
>matching network?

No, not every mechanical filter will work.  The older filters
have a 100K impedance to work with vacuum tubes.
The newer mechanical filters before the torsion bar filters
are lower impedances, suitable for use with solid state
circuitry, typically 2K, but sometimes higher or lower.


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