Topband: RFI Sense antenna or preamp needed ?

[Charlie]

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 at charter.net
> Date: Sat, 31 Oct 2015 18:46:59 -0400
> To: Topband at 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
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband