Topband: Re: [160m] low noise ants

[Tom Rauch]

> and a full 1/4 wave virtical for 40m has anyone got any plans for a
> low noise ant i could use on 160/80m woulb a snake ant be anygood or
> how about a large mag loop useing rg58 and dk9sq mast with cross
> members to make a dimond shape any help welcom chris g0wfh

Chris and others,

This question comes up frequently, and a brief summary might be 
useful.

Magnetic loops can offer improvement in S/N if you have local noise 
from one primary direction. For skywave noises or QRM, they are 
somewhat useless. The "shield" is meaningless, except a properly 
implemented "shield" can sometimes improve balance of the loop. They 
are really NOT magnetic antennas, except immediately next to the 
antenna. At a distance of about 1/10th wavelength or so a small 
"magnetic" loop's response is primarily electric, and at about a half-
wave or further they are no different than any other antenna type you 
might use. In a location free of noise or interference coming from 
well-defined one direction in the loop's null they will not improve 
S/N ratio. 

K9AY Loops, Flags, Pennants and EWE's all work on the same 
principles, since they are all small terminated loops. They behave 
like small two-element vertical arrays, with an internal phasing 
system. The termination insures each "vertical" element has equal 
current, phase is inherent in the design and comes from the 
horizontal component of the wires.  They are primarily useful when 
noise or QRM is directly off or near the rearward direction.

These loop antennas (even the single unterminated loop) are all 
moderately low-impedance antennas, and despite rumors you CAN use a 
metallic mast with any of them as long as the mast is isolated from 
the element, not much taller than the antenna, and non-
resonant.

Snake Antennas are really just a "random luck" antenna. There isn't 
any science, reliability, or planning to successful installations. 
Sometimes you'll find a wire or antenna that helps under some 
conditions. It might be an antenna for another band (like an 80-meter 
dipole) that just happens by random chance to work, or it might be a 
wire strung out on the ground like a snake.

One thing all these antennas (like most smaller 160 receiving antenna 
system) have in common is results will vary greatly with each 
individual application.73, Tom W8JI
W8JI@contesting.com