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) <[email protected]> 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 _________________ Topband Reflector Archives - http://www.contesting.com/_topband
