Topband: New 160M high performance receiving antenna at W3LPL

[Tom W8JI]

>I have been wondering if the antenna element in phased arrays could be a 
>loop rather than a vertical. My thinking is that the loop has some level of 
>directivity so phasing two of them should result in better side lobe 
>suppression compared to a vertical. Is there any merit to this thought? 
>Specifically, will I see better RDF numbers if I were to use loop elements 
>in any of the active 8 and 4 circle systems (e.g., DX Engineering, Hi-Z 
>Antennas, etc.)?
>

Hi Rudy,

A loop can work in a fixed array, or bi-directional array. My first antenna 
allowing me to work JA's through LORAN from Ohio was a long array of loops, 
although these were elongated loops. I also had long end-fire arrays of 
small inverted delta loops in Cleveland in the 80's, and small active 
verticals.

Small loops do not work well when used in things like four squares or 8 
circle arrays. A multiple direction array, like a four square or 8-circle, 
requires a uniform pattern of uniform phase from each element or cell.

With a small loop, phase flips 180-degrees immediately after crossing the 
null. Also, the directivity is generally poor because the small loop has two 
very sharp null points though the loop axis, but a broad response everywhere 
else. Both of these things actually hurt performance of arrays with loops 
that depend on phasing to eliminate side nulls.

Elongated loops are a different story, because (we probably all know) 
elongated loops are not really loops in function. They are really phased 
verticals, and the horizontal part or component of the conductors is simply 
a phasing line. K9AY's, Flags, Pennants, EWE's, and other forms of elongated 
loops are really all just phased verticals in function. They have a wider 
null and no sudden phase shift at the null, and no null cone at the side or 
"loop axis".

The best element for a traditional 8-circle or four square will always be a 
simple vertical, and even in a broadside array we would want to avoid small 
loops with deep axis nulls. They are OK as cells in an end-fire array, but 
not particularly advantageous for pattern unless elongated. I used small 
loops as a matter of "construction convenience" as deltas in a long endfire 
array, but the deep side null in that array was really created by 
out-of-phase cells of deltas and not the sharp null pattern of the 
individual delta. It could have just as well been verticals with no loss of 
pattern.

73 Tom