[TenTec] Orion 2 HW Noise Blanker

[Dr. Gerald N. Johnson]

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