A couple of issues I see. It depends which direction(s) the noise and desired signal are coming from. You may null the noise and signal. Also, the loop is bi-directional.
I've been playing with a DX Engineering RF-PRO-1B at ET3AA and it works. Thanks to Tim and the gang for their support. But there is a lot of noise and not being able to null everything except the desired direction I suspect is an issue. Our noise is close in, so I have some upgrades in place using a Hi-Z 4 square and NCC-2 with a "noise" antenna as Frank mentions. Unfortunately the next thing I need to do after I send this, is to cancel my reservation for the 27th of this month. Africa looks like a pretty safe place Covid-19 wise at the moment. But one look at the long lines at immigration did me in. I don't have the patience for that. 73 Ken K4ZW On Sat, Mar 14, 2020 at 11:43 PM <donov...@starpower.net> wrote: > > > Hi Rick, > > > > A noise receiving antenna close to a noise source is used in conjunction > with a higher performance receiving antenna such as a Beverage or an > array of short verticals and a passive or active noise canceller. > > > > A small loop antenna provides a mechanically steerable null off of both > sides of the loop. Null beamwidth is just a few degrees at the 3 dB > points, otherwise a small loop is an omni-directional receiving antenna. > Simply turn the loop to minimize the interfering noise signal strength. > > > The smaller the loop, the deeper the null depth but the smaller the signal > strength of desired signals. A small loop antenna requires a low noise > high gain pre-amp directly at its feed point for optimum sensitivity. > > > A small loop antenna should be close to ground for optimum null depth. > Horizontally polarized skywave signals penetrate the nulls if a small > 160 meter loop antenna is much higher than than about ten feet above the > ground > > > On 160 meters a small loop antenna provides: > - a 30 dB null off each side of a 5 foot diameter loop. > - a 25 dB null off each side of a 10 foot diameter loop, or > - a 20 dB null off each side of a 17 foot diameter loop > > > 73 > > Frank > W3LPL > > > > > > > > > ----- Original Message ----- > > From: "Richard (Rick) Karlquist" <rich...@karlquist.com> > To: "Dave Cuthbert" <telegraph...@gmail.com>, n...@arrl.net > Cc: "Topband" <topband@contesting.com> > Sent: Saturday, March 14, 2020 10:17:59 PM > Subject: Re: Topband: Slightly OT - amplifier noise > > > I am trying to understand what these noise cancelling > schemes do that couldn't be done with a simple loop > (rotating the loop until the noise drops into one of > the null directions). You can easily prove to yourself > with a hand held AM BCB receiver equipped with a ferrite > bar antenna that even the worst power line noise can > almost always be greatly suppressed by properly rotating > the receiver. Similarly, I have had good luck with > small tuned loops (10 feet perimeter) nulling power > line noise. Smaller loops seem to have deeper nulls. > > It is critical to keep loops away from your other antennas > and power wiring. Otherwise, they will not exhibit a > good null. > > Rick N6RK > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector