Stefan Wolfe wrote:

I stated it improperly. I agree that total radiation efficieny in all
directions does not increase but I believe efficiency as a vertical radiator
(ie in the horizontal plane) does increase with G5RV at some frequencies due
to the ladder line. See http://www.roadkill.com/~unwin/G5RV.html

Oh, no, you've been reading Art's postings! He uses the term
"efficiency" in creative and inscrutable ways.

When used with respect to antennas (and a lot of other things),
"efficiency" has a universally understood, precise definition. The
efficiency of an antenna is the ratio of the power radiated to the power
applied. What you meant was effectiveness, not efficiency. If you do
find it necessary to use "efficiency" to mean anything other than what
it's universally understood to mean, you'll need to carefully point this
out at the time, or people are bound to misinterpret what you've said --
as I did.

If you prevent the
feedline from radiating, the power it would have radiated ends up being
radiated by the antenna instead.

Of course, this is correct. However, when you're cramped for space and are
trying to get as much RF as possible in the horizontal plane (rather than
warmimg clouds directly overhead :-)), it is advantageous to intentionally
use the vertical ladder line as a radiator when possible. At least, that is
the theory of one who has always had to use attic antennas. Fortunately I
will retire soon and will be moving to a place where I can put up a 160m
horizontal dipole if I wish.

So what you're doing is intentionally making or allowing the feedline to
radiate in order to get some vertically polarized radiation so you can
get more radiation at lower angles from a low antenna. That's a method
some of us would avoid, but in circumstances like yours it's very likely
one of the best solutions available.

Roy Lewallen, W7EL