[RFI] Ideas for ANC4 sense antenna to cancel out local noise

[Kenneth G. Gordon]

On 1 Nov 2015 at 7:01, Goldtr8 (KD8NNU) wrote:

> I have an intermittent RFI issue that comes from a subdivision about a 1/4 mile
> away.   To combat the noise I have been trying to use my ANC4 and I built a
> sense antenna out of an 80m hamstick that I put 20 feet in the air yesterday for
> a trial to cancel the noise on 80m (cheap and easy experiment).

According to a recent article in Electric Radio Magazine on "Noise Reduction 
by Phasing" by Mike Murphy WU2D, in many cases the only properly 
effective sense-antenna for such a phasing device is an exact copy of your 
regular receiving antenna. This is impossible in most cases, but does give 
one a "clue".

The ANC-4 does contain a pre-amp, as does the MFJ model, but those 
cannot possibly cope with the signal levels you are experiencing.

Secondly, in my experience, the hamstick is not a particularly efficient 
antenna for normal use, therefore I would think it would also not be 
particularly effective as a sense-antenna either.

Thirdly, loops have been used for years as particularly effective 
"noise-nuller". Therefore, in my opinion, your experiences with your loop 
should be discounted in this case. The result from your dipole, however, 
seems more meaningful to me, but it must be interpreted accurately.

Suggestions by Sigi appear to me to be very good, and I would suggest 
following his advice with regard to your radials, if possible.

Lastly, and again in my opinion, use of the ANC-4 in this case is a "stop-gap" 
measure, and the really only truly effective solution is to track the garbage 
down and eliminate it. This usually is a rather big and time-consuming job, 
but will result in the best solution.

The ANC-4, by the way, is a very good unit, and when used properly will 
provide very noticable and effective noise reduction.

Good luck. I might add that one of my pet peeves is unnecessary RFI and 
noise, and it is getting worse all the time.

Ken W7EKB