[TowerTalk] quad vs. yagi @ low height

[w8ji.tom]

Hi John,

> I prefer the delta loop elements as I have had better success with loops
at
> low heights compared to dipoles.  I think part of the answer is that
loops
> have a higher radiation resistance for equal height and are somewhat more
> efficient for that reason.  

If we use the IRE definition of radiation resistance (total power radiated
as EM energy divided by the square of net or effective current causing the
radiation), the quad element has slightly LOWER radiation resistance than a
simple dipole element.

As a consequence, if it has fixed loss resistance, it has less efficiency.

The explanation would be rather lengthy, but feedpoint resistance
(sometimes called "radiation resistance") has little to do with efficiency.
If you took the very same wire used in a delta loop, and made it into a
simple dipole in exactly the same environment, efficiency would be a tiny
bit better with the dipole. In either case the difference is not worth
considering.

73 Tom

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