Topband: Looking for 160m narrow beam RX advice - an interesting combination of ideas

[Lloyd Berg - N9LB]

Thanks for the input.

Yes, utilities are underground, located by the road - north side of
property.
This is adjacent to the proposed RX receiving area.
I can detect no noise coming from these underground lines.

South side of the property (adjacent to my backyard transmit towers) is idle
farm land - no nearby noise sources.
I can't put antennas on the farm property because of heavy snowmobile use in
the winter.
Residents of my rural subdivision must cross the farm to get to the
extensive snowmobile trail system.


-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com]On Behalf Of Tom
W8JI
Sent: Tuesday, January 06, 2015 5:58 PM
To: Lloyd Berg N9LB; topband at contesting.com
Subject: Re: Topband: Looking for 160m narrow beam RX advice -
aninteresting combination of ideas


> Finding a single RX antenna system that nulls the neighbor noise sources
> at 90 and 270 degrees is proving to be a challenge.

If the noise sources are really at 90 and 270, and you have 30 feet or more
for spacing at right angles to that, it should be fairly simple. Use a 180
degree out-of-phase array of two close spaced elements.  If you want to make
it directional in the main response, it would take two cells.

You could just use two small loops in line with the nulls oriented at 90 and
270, and phase them for a unidirectional pattern.


> I could place a "noise antenna" next to each neighbor, mix the
> equal-length feed lines together ( in phase ) for the noise source null,
> and then place the actual receive antenna (in-line verticals, loops, K9AY
> or Shared Apex ) right in the very center of my yard (
> centered/equidistant from the noise antennas ).

It would not be that simple.  You would have to match the levels, and have a
proper main antenna.  You could do that with a "fader" at the combiner and
the correct main antenna, but it would be much more simple to build a
directive antenna with deep nulls to the sides.

> Has anyone used multiple noise antennas feeding a single noise canceling
> device?

I haven't. The odds of that working without independent phase shift and
level control from each noise antenna is somewhat low, because it is
unlikely the levels from sense antennas will independently have equal phase
and level relationships to the main RX antenna you are trying to remove
noise from.

You are assuming the relationship of noise at common for sense antennas is
the same phase and level relationship, allowing for some rotation that can
be compensated out, as to the main.

I don't think that is likely without some way to adjust each noise sense
antenna independently.

Far less complex would be using cells that null the sides where the noise is
(easy since they are 180 degrees apart).

If the individual cells do not hear the noise, they will not hear it when
combined.


> Has anyone cascaded/combined a noise canceling device such as the NCC-1 or
> MFJ-1026 with a traditional short RX vertical(s) array or loop(s) or K9AY
> or Shared Apex?

I have and I'm sure many others have, also. The problem is you have noise
from two directions and two sources. The blessing is they are 180 degrees
apart. If I were you, I would use a few small loops in an array. Real small
loops with deep axis nulls, not loops that are configured to act as end fire
verticals (K9AY, flag, pennant, etc), would null 180 apart very deep.

This of course assumes the noise sources radiate from the directions you
indicated. That might not be where they really radiate from, that just might
be where the houses are. They might be radiating from multiple places spread
over a large area, like back-feeding power lines with noise.

Are the utilities underground?

73 Tom

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