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Topband: Tuneable Cohen filter for 160m phasing receiver

To: topband@contesting.com
Subject: Topband: Tuneable Cohen filter for 160m phasing receiver
From: Steve Ireland <sire@iinet.net.au>
Date: Sat, 11 Oct 2003 15:25:30 +0800
List-post: <mailto:topband@contesting.com>
G'day

I have started to collect parts for a 160m phasing transceiver, using a
tuneable Cohen filter on its front end, based on the one in 'A High
Performance Receiver for 160 meters' on page 133 of 'Solid State Design for
the Radio Amateur' by Wes Hayward W7ZOI and Doug De Maw W1FB.

The book was published in 1986 (!) and James W. Miller no longer
manufacture the slug-tuned coils used in the design.  These are:

J.W. Miller 43A685CBI (2 required), which is 38 to 68uH, with a Qu of 175
at 1.8MHz and is slug-tuned and in a shielded can

J.W. Miller 43A154CBI (2 required), which is 95 to 187uH, with a Qu of 175
at 1.8MHz and is slug-tuned and in a shielded can.

J.W Miller 9054 (1 required), which is 42uH, with a Qu of 50 at 1.8MHz.

Owing to the configuration of a Cohen filter, this means that the
slug-tuned cores can't easily be replaced with toroidal cored coils.

Does anyone know of any stockist that still has a supply of the old J.W
Miller coils, or have any ideas about similar high-Q slug tuned coils that
could be substituted for them?

ANY help would be gratefully appreciated.

Vy 73

Steve, VK6VZ



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