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Re: [TowerTalk] Narrow Band Filters

To: "Michael Tope" <W4EF@dellroy.com>,"Jim Lux" <jimlux@earthlink.net>,"Jim Brown" <jim@audiosystemsgroup.com>,"Tower Talk List" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Narrow Band Filters
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Mon, 5 Jul 2004 12:07:15 -0400
List-post: <mailto:towertalk@contesting.com>
> A phasing unit like the MFJ will work and have plenty of
dynamic range,
> but it would require a bit of work to get it setup and
adjusted. It might be
> practical for a really serious Field Day effort, but my
guess is that you
> would need one guy who did nothing else but handle the
phasing unit
> design, installation, troublshooting, and adjustment. Our
Field Day usually
> doesn't have enough workforce to make that practical.

The MFJ unit has totally inadequate dynamic range for this
application, and it is the best of all the units I have
tested.

The idea of an HF filter for in-band rejection of different
modes is useless, unless very expensive. Even helical
resonators would have inadequate Q.

Even on 160 meters deep rejection at 40kHz requires very
good components. I had to use multiple Q~500 inductors in my
BPBR filters on 160.

73 Tom


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