Jeff,
I have sometimes had the same experience. It seems to me that when
you use a very narrow filter in noisy conditions, and assuming the filter is
not ringing, making things worse, what you end up hearing is a narrow band
of frequencies with your intended signal mixed in there somewhere. Even
though it's no stronger against the noise when the passband is wider, your
ear has an easier time picking out that single frequency when everything
else around it doesn't sound like almost the same frequency.
By the way, there is one TT (Network Science) filter that I have
noticed in the Omni VI/+, as others have on the reflector, that is like a
miracle in noise, and that's the 6.3 MHz 250 Hz CW filter. Wow, the job it
would do to help pull a signal out of the noise really surprised me. Most
other company's narrow filters ring like crazy, but the TT ladder filters
really got it right.
73, Duane
Duane Calvin, AC5AA
Austin, Texas
www.ac5aa.com
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Jeff Frank
Sent: Saturday, June 16, 2007 8:19 AM
To: TenTec@contesting.com
Subject: [TenTec] WIDER FILTER FOR WEAK CW DXING?
I have an Omni 6 opt 1, which I like very much, but on weak cw signals, my
experience with the filters seems counter-intuitive. I almost always have
easier and clearer copy on weak cw signals when I use the 1.8 khz filter vs.
the .5 or .25 khz filters in my 6.3 mhz IF. I've got nothing in the N1
position. Is this the way it's suppposed to be? I always thought narrowing
the filter bandwidth is supposed to cut down on noise but it seems opposite.
Has it got something to do with receivers that are optimized for adjacent
signal rejection vs. signal to noise ratio? I think I read that somewhere.
Can anyone explain this to me? Thanks.
Jeff Frank
(KX2P)
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