Dave wrote:
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!!!!

From "Antennas For All Applications", 3rd edition by
John D. Kraus and Ronald J. Marhefka, page 665:

"Turning now to the *beam efficiency E(m)*, or the
ratio of the solid angle of the main beam Omega(m)
to the total beam solid angle Omega(a), we have ..."

All emphasis is the book author's, not w5dxp's.

From "Antenna Theory, Analysis and Design", 2nd edition,
by Constantin A. Balanis, page 63:

begin quote:
2.10 BEAM EFFICIENCY

Another parameter that is frequently used to judge the
quality of transmitting and receiving antennas is the
*beam efficiency*. For an antenna with its major lobe
directed along the z-axis (Theta = 0), as shown in
Figure 2.4(a), the beam efficiency (BE) is defined by

power transmitted(received) within cone angle Theta(1)
BE = ------------------------------------------------------
power transmitted(received) by the antenna

end quote:

In trying to figure out what definition Art is using,
this definition seems to me to be the closest.
--
73, Cecil http://www.w5dxp.com