Bill Turner wrote:
ORIGINAL MESSAGE:

Tom, W8JI wrote:
"A reflector does not reflect anything. It radiates."



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Tom could have said "it reflects by radiating".

Semantics count here.

73, Bill W6WRT

That's an interesting point. Suppose you have a two-element driven array
with the elements spaced a quarter wave apart and fed 90 degrees out of
phase. This produces a cardioid pattern, which has a deep null. Is the
element toward the direction of the null "reflecting" and the other one
"directing"? If so, what are they "reflecting" and "directing"?

Each element intercepts considerable energy from the other and
reradiates it, if that makes a difference.

Here's another one: Build a 4 square array, assuming the ground is
perfect. (The EZNEC example file 4Square.EZ or demo equivalent
d_4Square.EZ can be used to illustrate this.) If you disconnect the
feedline to the rear array element and short circuit the feedpoint (by
deleting Source 1 in the EZNEC model), you'll still have a moderately
good directional pattern with about 15 dB front-back ratio. The rear
element is now a parasitic element, which we like to call a "reflector".
You've said it "reflects by radiating". Now connect the rear element
feedline as in the original antenna. The front/back ratio improves. But
the feedpoint resistance of the rear element is negative. This isn't
particularly unusual in driven arrays -- it means that the element in
question is absorbing power from the other elements and sending down the
feedline toward the source. The element is still radiating, because
current is flowing on it. But it's absorbing more power from the
surrounding region than it's giving back in the form of a field. (Again,
the excess is being sent back along the feedline to be used by the other
elements.) So, is that element now "reflecting"? If so, is it
"reflecting by radiating"?

Roy Lewallen, W7EL