We should remember that historically, loops were developed for direction
finding. In that application sharp, deep nulls were important. In addition
symmetrical patterns were desired that did not change as the antenna was
rotated. Both of these depend on symmetry and the balance of the antenna in
relation to its surroundings. Shields were introduced to make balancing
easier, especially when a standard antenna was being used in a wide variety
of installations with little control over the surroundings. Initially the
Faraday shields actually enclosed the entire antenna. The shield was a cage
of horizontal loops, connected together by one conductor on the side
connected to ground. The coaxial design was just more practical.
Whether or not the RDF considerations really matter to amateur use is open
to question. With reasonable care in construction adequate balance in a
simple open loop can usually be achieved. At least for our purposes. The
only other advantage attributed to a shielded loop is that it is much better
when precipitation static is a problem.
In day-to-day operation my loop is seldom as good as my array or Beverage
but occasionally it is helpful to reject a annoying noise. One example
would be strong signals during a contest. I find that I can frequently null
out the big guy and work the little guys under foot. Rather like hunting
mice under the feet of elephants. The loop was easy to make and I put it on
a TV rotor, up in the clear.
BTW the earlier reference was King, Mimno and Wing not Young.
73, Rudy N6LF
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