I have periodic episodes of severe power line noise.
What works great for me is a simple short vertical (20 or 21') ground mounted
and using one of the Hi Z high impedance preamps at the feed point. Ground is
a 3 or 4' copper clad ground rod. No radials. These are the preamps that
come with their 2/3/4/8 element array, purchased separately. It is 12VDC
powered through the coax. It can usually pick up most of my power line noise
sources with enough strength to be used for nulling. I have also used a DXE
amplifier off one of their active antennas but with a 20 or 21' vertical and
this works great as well. It likely would work OK with one of the short
whips that come with the DXE antennas also.
At first we used the MFJ1026 but replaced it with a DXE NCC-1 noise
cancelling/signal enhancing unit. The MFJ was useful but this NCC-1 is one of
the best investments in an accessory ever made here. I have used it for
signal enhancement and noise nulling. It has four levels of attenuation on
each of the two antennas 0/-10/-20/-30 db plus a smooth working balance knob
which fine tunes the levels between antennas. The huge phasing knob is smooth,
plus it has toggle switches to reverse the antennas and reverse the phase on
the B antenna. This last toggle switch (B phase Norm/Rev) switches from a
null to a peak instantly, or vice versa.
I have lost track of the DX which would not be in my log without the ability to
null my power line noise. Sometimes this noise is most severe on the higher
frequencies, and the noise antenna working against the main tx antennas usually
is a very effective combo. I can sometimes go from S9 plus noise to S1 or 0
with the NCC-1. The key is that the level of the noise on the noise antenna
should be as high as the noise level received on the main antenna. Otherwise,
you have to attenuate the main antenna to get the noise levels in balance. When
you do that, you also attenuate the desired signal. This sometimes still
works OK but for best results the noise antenna should hear the noise equal or
better than the main antenna.
Hopefully some day the power company will address my issues and we can go back
to using the NCC-1 as a signal enhancer.
73 Charlie N8RR
> From: goldtr8@charter.net
> Date: Sat, 31 Oct 2015 18:46:59 -0400
> To: Topband@contesting.com
> Subject: Topband: RFI Sense antenna or preamp needed ?
>
> I have a lot of RFI at my QTH on 80 & 160m. I have an ANC4 that works if I
> can get enough signal to cancel the interference.
>
> I just put up a sense antenna 20ft high using an 80m ham stick and don't have
> enough gain to cancel the noise out.
>
> So I need some ideas for either a sense antenna with higher gain or finding a
> preamp to boost the signal to do the cancelling.
>
> Any and all ideas or comments are welcome.
>
> Thanks
> Don
> KD8NNU
> Sent from my iPad
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