On Sat, 11 Oct 2014 11:47:22 -0500, John S
wrote:

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

Sounds about right except that it doesn't include any losses
introduced by the necessary matching network and real ground losses at
HF frequencies. Expanding my table to include radiation efficiency:

http://802.11junk.com/jeffl/antennas/Monopole/index.html
Length Gain Radiation
wl dBi Efficiency
0.050 4.75 99.09%
0.125 4.85 99.66%
0.250 5.19 99.93%
0.500 6.96 99.97%
0.625 8.01 99.93%
In other words, there's nothing inherent in the length of the radiator
that would affect radiation efficiency. If there is a drop in
radiation efficiency, then it's mostly due to ground losses, material
losses I2R, and matching losses).

I invite discussion in any case.

NEC: Power Efficiency vs. Radiation Efficiency
L. B. Cebik, W4RNL
http://www.antennex.com/w4rnl/col0504/amod75.html
Lots of examples of how "efficiency" calculations work, and how
various common antenna configurations affect the results. (I need to
re-read the article as there's plenty about this which I don't
understand very well). Test cases 5 and 6 are short monopoles, which
should have something to do with short dipoles. From the bottom of
the page:
"Unlike the vertical monopole, the horizontal dipole shows much
more regular changes of radiation efficiency with changes of
soil type, ranging from 80.01% over very good soil to 65.93%
over very poor soil."

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558