[TenTec] Capture area (was 80 meter loops)

[Jim Reid]

Sinisa has written:

> Regarding "capture area", please note that
> it is NOT separate from directivity (loss ignored).

In fact,  for engineering use,  the term "capture area"
comes from the use of horns and parabolic reflectors
for UHF and higher frequencies.  If you have a look
at the formulas for capture area you will see that
Gain is a part of the expression.

And,  as Sinisa has said,  the wave front must be coherent
across the aperture of the antenna being viewed as having
a "capture area".  Bell Labs,  I believe,  first used the idea
of capture area for the big sartorial horns they developed
for long distance microwave signals service.  It might
also have originated at the Radar Labs from MIT in their
series of volumes put out after WW II.  Don't think the
term pre-dates 1940 or so.  Anyone know for sure?

Capture area for HF antennas is a rather useless
unless perhaps part of the design for really large 
V-beams and Rhombic antennas  and,  again,  I
am not really sure you can view the wave front
onto such types as coherent,  or truly in-phase
over the entire set of wires comprising these
antennas.  My thought now is,  that the term is
not really applicable to these sorts.  Perhaps
others will know for sure!

73,  Jim  KH7M