[RFI] Noise Cancellers - RFI Survival Guide

Christopher Brown cbrown at woods.net
Sat Nov 11 18:07:26 EST 2017

Exactly, on all counts.

I have one of the MFJ models.  I found it useful years back when I had a
single _strong_ source swamping things (it turned out to be a very nasty
computer PS at a nearby house).

In order to get it to work I have to place a pre-amplified small loop at
the edge of the yard closest to the source (maximize noise pickup and
minimize all else) and very carefully adjust the canceler.

Connecting to something other than a noise pickup specific antenna (like
my second HF antenna) would allow me to cancel one thing, at the expense
of bringing up other noise.

Total pain to use, but allowed be to operate untill the source could be

It has been sitting on the shelf for a number of years now,
why...Because while I do have more than a little noise, currently it is
the summ of _many_ weak sources...If the noise is raised floor from lots
of different sources a canceler is useless.

If there is a single strong noise source that you cannot eliminate,
_and_ you can manage a "noise pickup" antenna that receives that signal
strongly but not so much the desired signals, could be useful.

On 11/11/17 07:37, Hare, Ed  W1RFI wrote:
> Noise cancellers can be 30 to 50 dB effective against a single source of noise.  They work by positioning a sense antenna that will pick up more noise than signal and combining that out of phase with the signal plus noise from your main antenna.  That can be very effective. 
> They do have disadvantages, though. They don't work against multiple noise sources. They are tricky to set up and tune and if you QSY a few tens of kHz, you need to retweak the settings.  They will also change the receive pattern of your antenna, so if you are using a directional antenna, your "noise" antenna will pick up signals from all directions, perhaps degrading your front-to-back ratio.  And, no matter what, they will put a null in your receive pattern in the direction of the noise, so in that direction, you will pick up less signal, too.
> Ed, W1RFI/5
> ________________________________________
> From: RFI [rfi-bounces at contesting.com] on behalf of Tom Lewis via RFI [rfi at contesting.com]
> Sent: Saturday, November 11, 2017 8:39 AM
> To: RFI List
> Subject: [RFI] Noise Cancellers - RFI Survival Guide
> Does anyone know if this works?
> 73 Tom N4TL
> ==============================================
> Earlier this year, I published a series of articles on my web site called "Noise
> Cancellers - RFI Survival Guide". The purpose of this information was to help hams and
> shortwave listeners lower their local HF noise floor and improve reception.
> RFI from neighbors is a constant challenge.  Properly set up, noise cancellers are
> amazingly effective in cleaning up or reducing RFI. Sucesss depends on understanding what
> kind of noise you can fight, how noise cancellers work, and most important, designing and
> installing noise probe antennas around your location. This five-article series does just
> that. It also includes a detailed video demonstrating effective noise cancellation.
> Please take a moment to review these articles. If you find them to be useful, please
> consider passing these along to your members or contacts.
> You can use these articles by linking to them on your web site, Twitter feed, Facebook
> page or by e-mail. The URL is:
> http://play.fallows.ca/wp/series/noise-cancelers-rfi-survival-guide/
> Thanks for your consideration. If you have any questions or suggestions, please contact
> me.
> 73 John Fallows VE6EY
> Calgary, Alberta
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