John Smith wrote:
Cecil Moore wrote:
Jerry Martes wrote:
How does Art define Efficiency for evaluating Yagi antennas?

I don't know - I just joined this thread in the middle.

Cecil:

I think caution is best used. Reminds me of the three blind men who
went to see the elephant, one grabbed the trunk, one a leg, the other a
tail... and you know how the story goes from there.

I think there is confusion between the radiated power, only allowing for
resistance/dielectric losses; as opposed to why it is desirable to allow
some loss introduced by other elements because the net gain of
"focusing" the antenna is a benefit to you is the major crux of this
whole discussion. But then, I am not even sure of that, completely!

I suppose the most "efficient" antenna, with only taking into
consideration the power delivered to the antenna though the feed line
and actually arriving at the feed point to the antenna as the "antennas
input power" in relation to the actual "power radiated" (or delivered to
the ether) is what Art is looking at. And, in this one regard, I would
suppose a full wave dipole with large dia conductors (to allow for skin
effect), silver coated conductors and glass insulators would be the most
"efficient antenna" (and allowing for a "perfect match" setup being
installed.)

But, where is that power going into the lobes may not make it the most
desirable antenna!

In the yagi, because the reflector and director are so close to the de
in terms of wavelength do introduce some trivial? (depends again on
perspective) losses here.

And, here comes the fairies and the pinhead.

JS

Of course, I always think of the parabolic reflector antenna as the
"most efficient!"

I have never seen one constructed for 160m (strange huh?); but when you
get into ghz, why would you ever use anything else? (well, unless you
wanted to chat off to someone on the side or back.)

JS