El 01-04-14 19:21, Channel Jumper escribió:
Radials on a elevated antenna only works if the radials are placed at or
near the bottom of the antenna and are arranged at a 45* angle.

Any other angle and you might as well not have any radials at all!

I don't support this reasoning, I see many good antennas that don't
follow this rule.



On a 10 -12 meter antenna, these radials would need to be at least 1/4
of a wavelength long - 9 feet and preferably 18 feet long to do any
good!

If you coil them up they do not work as intended, but they might help a
little.

Forget calling them a ground plane, think of them more like a mirror.

I see the ground provision just as a means to pull out the current
that goes into the radiator (as I don't want to draw this current out
of the braid). If 1 A goes into the radiator, I need to draw 1 A from
my ground/counterpoise/etc. I would like to have the resistance of the
ground provision small with respect to the real part of the radiator's
impedance.


If you shine a beam of light directly at a mirror, the light is 100%
reflected back towards the source.

I think you can't compare the light analogy with a situation where the
wavelength is no long small compared to the structure.

A ground provision can be good enough for a well-designed half-wave
end-fed antenna, but useless for a quarter wave whip. You can't
explain this with light analogy.



If most of your radiated power is located at the bottom of the antenna
and you can reflect that power up and forward - it is going to radiate
better then something that is only partially effective.

Anything that you don't reflect is adsorbed into the ground - good for
keeping the worms warm at night, but not good for radiating RF..

Only a fool would become a ham and then move into an apartment!

Sometimes you don't have another choice and then you need to get the
best out of it.


The sad truth is that most people do not understand what being a ham is
all about anymore and most people thinks that amateur radio is a right
and not a privilege.

Trying to be a ham while living in an apartment building would be like
trying to be a Ocean liner captain while living in Oklahoma...

The metal railing is much too small in rf area to be an effective
counter poise - sorry but who ever told you this should go back to
school and get a real education.

It all depends on the current you need to draw from it, given certain
power. You will certainly not get good radiation efficiency, but this
doesn't say it is useless.

Given the good conditions at the upper end of HF, you can get useful
efficiency from a small antenna.


--
Wim
PA3DJS
Please remove abc first in case of PM