Carl, that's true, they do take a bit of time to fine tune, but once
tuned, you usually don't have to retune much.
So you may lose a QSO or two, but afterwards you can operate.
I have never used the MFJ so I cannot comment on it.
I can only say that I rarely saw my two units because the boys here in
the Bavarian Contest Club were always loaning them out for contest
expeditions.
73
Rick
Carl Moreschi wrote:
I had an MFJ 1026 noise cancelor for a while. I found it quite effective at
removing various noise sources but there were problems with it. I had an
outside noise antenna for it. The noise antenna did not hear the noise as
well as my normal antenna. So I typically had to reduce the signal from the
normal antenna to match the strength from the noise antenna. Then I would
have to adjust the phase to get the noise to cancel. This usually took
about a minute to get everything adjusted properly and all the noise
removed. At that point the signal I was trying to hear usually left and was
gone! I sold my noise cancelor a few months ago.
Carl Moreschi N4PY
121 Little Bell Drive
Bell Mountain
Hays, NC 28635
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
To: <tentec@contesting.com>
Sent: Monday, January 29, 2007 4:56 PM
Subject: Re: [TenTec] Orion 2 HW Noise Blanker
On Mon, 2007-01-29 at 16:26 -0500, joel hallas wrote:
Jerry,
That not quite what Toby's talking about.
The old noise blankers used a noise sample in a wideband receiver to
perform a short (not extended by selective filters) duration receive
mute, much like current noise blankers operate except they pull a sample
at the operating frequency from early in the receiver.
The noise cancelers work in a different way. Instead of shutting off
the receiver they have a phase and amplitude adjustment that allows the
noise reduction signal to cancel the input from the regular antenna.
This allows removal of even CW signals, or in band QRM if the directions
are different. See Aug 06 QST, p 45 for more, if you like.
73, Joel Hallas, W1ZR
Yah, I saw "noise xxxxxer" with separate antenna and thought noise
blanker with 40 MHz noise input.
Noise cancelers at the antenna work on the noise antenna capturing full
strength noise but not much for signal which to me seems more than a
little serendipitous, especially with more than one noise source. Using
elevated directive antennas for both leads me to believe that the
"noise" antenna wouldn't get the noise the same strength as the main
antenna but would often acquire unwanted signals on the same frequency
from the direction the noise antenna was aimed. Might as well listen
with a vertical, "equally noisy in all direction." Seems to me the
directive antenna (admittedly its inconvenient to get directivity on 160
meters on a city lot with anything larger than a 2 meter diameter multi
turn loop) may be a better investment in S/N unless the noise source is
extremely local and then it might be most profitable to cure that noise
on the ham's own premises.
I could envision three towers with identical beams all pointed the same
direct (that of the desired signal and some DSP processing with three
front ends to determine the direction of the unwanted and then to do
some directional enhancement, but I question whether it would do better
than just phasing the extra beams for better horizontal and vertical
directivity.
E.g. I think the MFJ device (which they did NOT invent) will fail to
make an improvement more often that it makes an improvement. And one in
the receiver would do no better.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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