Topband: 160m & 80m RFI issues requesting ideas for ANC4 sense antenna to cancell out local noise

[Mark Schoonover]

I did a lot of experimenting with this vary problem. I have S9+ noise
leverl on 160-30m. I used the MFJ version because I like the ability to
control the gain on both sense and main antennas. I tried a 102" whip with
the same results as you. I then tried a 25' horizontal antenna and that was
less effective than the whip. What I ended up doing was taking a 10' crappy
fishing pole and helically winding about 50' of wire starting at the top
all the way to about 5" from the bottom of the pole. From there, a single
wire goes through the antenna patch panel to the back of the MFJ. I live in
a typical suburban area with neighbors about 20' away. I also have a 60KV
power transfer station about 100 yards from my home.

It took me awhile to get things nulled out. My main antenna for 160/80 is a
ladder-line fed 40m loop where I short the feedline together and run it
against a bunch of ground radials. Once I got things all worked out, I've
run several contests and from the San Diego area, I've been able to work
D4C on 160 & 80. I could hear Navassa on 80m but couldn't work them because
I didn't know my feedline had broke at 25' long! I've been totally amazed
with this noise reduction setup. I can usually get the noise level down to
S2 on 160/80/40 and can work everyone that I can hear.

My tuning process is to set the sense antenna gain at about S4, then make a
note of the setting. I then use the main antenna gain to bring the noise up
to S4. I return the sense antenna gain to the written down setting and
start using the null until I hear a distinct decrease in noise. I then keep
edging up both gains until the noise from the main antenna starts to
overcome the sense antenna. I back things down a tad and that's it. Once
the MFJ is set, I can move about the band pretty good. Might have to touch
up main antenna gain slightly.

Anyway, hope this helps! 73


4NEC2 The Definitive Guide: https://leanpub.com/4nec2definitiveguide
Website: http://www.ka6wke.net
Resume: http://cv.ka6wke.net

On Sun, Nov 1, 2015 at 4:01 AM, Goldtr8 (KD8NNU) <goldtr8 at charter.net>
wrote:

> HI Guys,
>
> 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).   The location of the sense antenna is at the corner of my lot
> as close to the subdivision that I can get.  The design is the hamstick as
> a vertical element and two 102 inch whips as elevated radials.
>
> The noise is s9 on my 1/4 wave 80m vertical and 160m inverted L.  This is
> a multi band vertical with wires for 40m, 80m & 160m.   I also have other
> antennas such as a 160m 2wl long loop and a trapped dipole.  What is
> interesting is that the noise is significantly less on the loop and the
> dipole.   I attribute this to the noise being vertically polarized based on
> my research on the internet.  Also this sense antenna is roughly 150ft away
> from the vertical antenna.
>
> The issue is the level of the sense antenna noise is significantly less
> than the vertical and I am not able to find a null point that makes a
> difference.   I can however use the loop antenna and I have enough signal
> with the hamstick experiment to get a null as the received level of noise
> on the loop is significantly less.  So I believe I need more receive gain
> on the sense antenna.
>
> So with the above in mind, is there a low cost pre-amp that I could use on
> the sense antenna to boost the signal?   Or what other ideas are there for
> a sense antenna.   I don’t want to put up another 1/4 wave antenna for
> sensing.   I have read where folks suggest putting 50 ft leg dipole at 5 ft
> above the ground for 80m & 40m but I think the noise is vertically
> polarized and this wont do much but I could be wrong and have been wrong
> before.
>
> I have room to try stuff on the property for antenna ideas so that’s not
> an issue.  However, I need the sense signal level close to the interference
> level or I have no chance to get a cancellation of the noise.
>
> Again any and all ideas is greatly appreciated.
>
> ~73
> Don
> KD8NNU
> 2014 3905CC Top Gun :-)
> -.- -.. ---.. -. -. ..-
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband