On Fri, 10 Oct 2014 20:08:51 -0000, wrote:
(...)

This group is the only one that I read where topic drift ocurrs almost
immediately, often on the first or second followup posting. In other
groups, it usually takes 5 to 7 messages in a thread to produce the
same result. The problem is that everyone (including me) tends to
post about things that they are familiar with, know something about,
or are passionate about the topic (even if they know nothing about
it). If the initial question or request for comments does not fit
these criteria, many people will simply warp the discussion until it
does. For example, I know something about the mecahanics of antennas,
something about using NEC models, and have a fair collection of
anecdotes and photos from my days in the 2way radio biz. However,
this thread is allegedly about antenna theory, where I am seriously
lacking. Since I don't want to twist the topic away from theory and
into reality, I haven't said anything worth reading (including this
rant).

On the contrary, I think it is quite a worthwile effort especially if
you summarize and publish the results for the benefit of all the arm
wavers saying things like "short antennas are poor radiators".

Good idea. I'm curious, but not curious enough to dig through several
hundred off topic comments to excavate relevent information.

Then you can discuss real data instead of arguing about what some naif
pulled out of his ass.

"Data is free. Information must be fought for"
(Former statistics instructor in college about 1968).

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html
It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

I also did a study of monopoles of various lengths above a ground.
There are a few that are less than 1/4 wave long which should help
with some short antenna phenomenon.
http://802.11junk.com/jeffl/antennas/Monopole/index.html
Length Gain
wl dBi
0.050 4.75
0.125 4.85
0.250 5.19
0.500 6.96
0.625 8.01
Notice that the gain doesn't really drop very much when the monopole
is shorter than 1/4 wavelength long. A 1/2 wave dipole exhibits a
similar lack of gain loss for short antennas. So, why are short
antennas generally frowned upon? Lots of reasons but the big one are
losses in the matching networks. the 0.050 wavelength antenna looks
like about 700 ohms impedance. The 0.125 antenna is about


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