RadioBanter - View Single Post - Dipole with inherent directional capabilities?

John Smith · December 3rd 06, 04:30 AM posted to rec.radio.amateur.antenna

wrote:
Art,

I want to know about this concept. Can you tell me how to build one?
By what means might it change the very simple calculation of efficiency
given in the long and rambling thread which I am trying to avoid.

Take an antenna, any antenna you can dream up, measure the power
radiated in each direction. Add it all up. Compare that to the power
fed to the antenna.

A 100% efficient antenna radiates all the power it's fed.

A 50% efficent antenna radiates half the power it's fed.

A 150% efficent antenna radiates half again as much power as it's fed.

Why is an inherently directional "dipole" different from a yagi in this
respect?

Dan

Dan:

I am not Art. However, the questions look so ridiculous, let me provide
some possible answers.

A 100% efficient antenna radiates all the power it's fed.
ANSWER: Impossible. Well, outside of a superconducting physics lab anyway
!

A 150% efficent antenna radiates half again as much power as it's fed.
ANSWER: Again, impossible at this time, maybe in the future? Perhaps
aliens know how to do that?

Why is an inherently directional "dipole" different from a yagi in
this respect?
ANSWER: A dipole has "inherently directional properties", perhaps given
it by its creator? God? The laws of physics? Aliens? Well, it just
has them! And, you ask, why are they different than a yagi's? Geezh,
does a darn dipole even look like a darn yagi? I mean, come on, give me
some room here! Ok, let me give you a clue, there is more metal and
dielectric material in the yagi, that is why! grin

I think the top, very top efficiency of a silver plated-glass insulated
antenna in earths atmosphere, and with ample surface area to less "skin
effect" (probably space too, but there is
moisture/oxygen/nitrogen/carbon dioxide/etc. factor to atmosphere) is
~98%. When we finally understand the ether's relationship to an
antenna, it would NOT surprise me if we can bring that close to
99.99999999999999, not a great improvement--but hey, it gives me
something to think about.

Regards,
JS