On Sat, 11 Oct 2014 21:49:11 -0000, wrote:

Jeff Liebermann wrote:
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:

There is no feed because it is the ANTENNA that is being analyzed, not
an antenna SYSTEM.

And while I don't know if the simulation included it, NEC can include
the ground losses for the ANTENNA.

I used a perfect ground for the monopoles. The NEC deck is shown
below the charts on each page. For example:
http://802.11junk.com/jeffl/antennas/Monopole/monopole_0_050/slides/monopole_0_050.html
http://802.11junk.com/jeffl/antennas/Monopole/monopole_0_125/slides/monopole_0_125.html
http://802.11junk.com/jeffl/antennas/Monopole/monopole_0_250/slides/monopole_0_250.html
etc. Only the length of the monopole changes.

Ground and I^2R losses of the antenna are shown by NEC.
Matching losses are NOT part of the antenna.

Agreed. I used a perfect ground and ideal conductors in my very
simplistic models. The idea was to demonstrate that there is nothing
inherent in the length of the antenna that would have a major effect
on the gain. I threw in the other losses because I wanted to offer
reasons for why short antennas are not particularly popular. It's not
the antenna that's the problem. It's all the stuff that goes around
the antenna (matching loss, balun loss, combiner loss, tuner loses,
resistive losses, height above ground, counterpoise/ground losses,
mounting structures, feed line losses, feed line radiation, etc).

Yep, and once the issue of size versus efficieny is put to rest, it would
not be a bad idea to look at the real effects of ground, both in terms
of height in wavelengths and soil quality.

Yep. I threw those into the discussion without providing anything in
the model to demonstrate their effects. I could/should do that, but
I'm busy/lazy this weekend.


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