Topband: Boradband noise on 160 meters tracked down to apartmentcomplex
wd8dsb at gmail.com
Mon Dec 15 11:01:24 EST 2014
Thanks, and my statement was too broad. In my case I am unable to meet the
conditions you mentioned (my sense antenna would not be much closer to the
noise, and it would not pick up the noise much better than the listening
antenna which is pointed in the direction of the noise source).
Thanks as always,
On Mon, Dec 15, 2014 at 10:08 AM, Tom W8JI <w8ji at w8ji.com> wrote:
> Mfj Nuller will not work because the signal is in the same direction of my
>> 300 deg pointing pennant.
> There are a lot of popular misconceptions about this. The noise does
> always not have to be a different direction, or even just one source.
> The MFJ nuller and other similar systems will remove noise when:
> 1.) The sense antenna is much closer to the noise, or picks up the noise
> much better compared to signals than the listening antenna does. This is
> true no matter what the desired signal direction. In this case you are
> eliminating a source by having a sense antenna hear the noise much stronger
> than the sense antenna hears desired signals.
> 2.) The noise is one or multiple sources from the same direction and the
> sense antenna is reasonably close to the RX antenna and the correct
> direction from the RX antenna. The noise has to be a significantly
> different direction than the RX direction. You are just eliminating the
> general noise direction in this case.
> 3.) The noise can be from multiple sources radiating from the same point.
> A long power line with multiple insulators arcing that is passing by close,
> and conducting emissions to that point, might be an example. You are
> nulling the point of coupling, rather than the noise generator's location.
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