Topband: Loop-family antenna notes

[Tom Rauch]

Hi Larry,

> After reading Gary's comments on the loop family antennas, I realized that
> I had left out one bit of information regarding the "Delta" performance.
> It seems that most of the delta performance degradation was caused by the
> 80 and 160 elevated radials and by the wire fence around the property.
> Horizontal stuff! While the degradation caused by the towers was still
> more that what was experienced with the flag and pennant, the horizontal
> stuff were the real killers.

Remember what a loop is. Near the loop it has response to 
anything that runs in almost any direction. The only place it has 
zero response is if the external conductor crosses the loops 
conductors at right angles, and only then if the electric field is 
balanced....

Even in the far field, these loops antennas have horizontal 
component for any direction except straight off the ends of the loop.

The far field pattern you are after with the terminated loop is 
because the vertical or partially vertical ends act like two small 
phased verticals. Unfortunately the horizontal or near-horizontal 
wires that act like "phasing lines" for the verticals also radiate.

Elevated radials certainly can make a situation worse, since the 
radials ALWAYS radiate and will couple to anything conductive at 
least within 1/2 wl or more around them.
73, Tom W8JI
w8ji@contesting.com


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