Cecil Moore wrote:

Dave wrote:

All other "definitions" are red herrings and do not contribute to the
answer.


Not if the question is: What is beam efficiency? :-)

ABSOLUTELY NOT!!!!

Efficiency is the ratio of [power input minus power losses] divided by [power
input]. PERIOD!!!!!!!!!

If it's anything else you have created a perpetual motion machine ... patent it!!!

This thread has been corrupted by confusion with directivity and gain. Neither
of which have anything to do with efficiency. Antenna patterns provide zero
information regarding efficiency.

It is possible, for this discussion, to have a Yagi with 10 dB gain, -60 dB
backlobes, and 10 dB losses and it is only a 10% efficient antenna that exhibits
a gain of 0 dBd. It is still 10% efficient.

Art, who made the original post, has to resolve his difficulties with antenna
efficiency, antenna system efficiency, path loss effects, gain and directivity.

Cecil, as an engineer, you should not slide into loose definitions of
efficiency. Doing so only further confuses the issue.

Art is using 'efficiency' incorrectly. His actual interest is in the total path
loss from transmitter to receiver and should be dealt with in that context. And
in that problem, path loss, the issues are further complicated between line of
sight, ground wave and over the horizon propagation effects. HF path losses can
have -60 dB variations, or more loss, depending on propagation, solar cycles,
and solar storms. We have all experienced QSB of up to 5 S units and also total
loss of signals due to solar effects. These effects are NOT YAGI ANTENNA EFFICIENCY.