On 8/3/2013 6:01 PM, John wrote:
I hope this does not add to the confusion too much. However...
Radials really only apply to quarter-wave verticals.
Well... er... um... not really. You want a nice
set of radials under an inverted-L antenna... and
other designs, also.
Bill Orr W6SAI (sk) says the folded unipole
requires a radial system, as does the Folded
Marconi antenna, and Extended Marconi, and
his book, and the ARRL Antenna Compendiums
have examples of various sloper antennas that
employ ground radials.
See Radio Amateur Antenna Handbook by Orr and
Cowan, Radio Publications, Inc.
A quick romp through HF Antennas for Everyone
by Read, G1MFG, published by RSGB, shows many
antenna designs that employ ground radials,
including some dipole designs, for example
the one depicted on p.43 that uses ground radials
on a dipole with window line vertical segment.
Just a few examples to illustrate ground radials
are used on many designs other than 1/4 wave
ground plane antennas.
A half-wave vertical only requires a ground.
Er... Um... there is serious disagreement on this
one, and many operators suggest a half wave
vertical can realize substantial benefit from
ground radials or a "counterpoise" - you can read
one cogent argument for this here:
http://www.w8ji.com/end-fed_1_2_wave_matching_system_end%20feed.htm
I think the gist of the argument is that it does
need some sort of counterpoise, or else the
choke balun must absorb all the return energy
or else your feed line becomes the return path
and acts as part of the antenna system. But
don't take my summary for it, W8JI does it way
better without my help ! ;-)
Although I have not
seem this, it would seem to me that for multi-band verticals, there
should be some isolation of the radials in order to maintain the desired
pattern for the upper bands.
Interesting... what do you mean by Isolation?
I am not being critical or funny here, but
don't the radials still need to be connected?
Not sure of the meaning of "isolated" in this
context.
These points illustrate why I am fascinated by ham radio- there are so
many facets, angles, and competing designs, ideas, etc., and so many
apparently contradictory elements, it seems impossible to run out of
things to research and learn about. I don't intend to be contrary, but
merely point out the complexity of it all, just using the above example
of the use of radials on many designs beyond the ground plane. There is
no end to any of this! ;-)
---------------- K8JHR -------------------
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