Elevated radials need not be tuned (whatever matching network is used
should resolve the tuning, BUT if the radials are to be effective in
cancelling the horizontally polarized radiation, pairs must be arranged
180 degrees apart. Yes, they can bend, but will be most effective if
the bends are symetrical and opposite. Remember the "ground plane"
antenna that was quite popular some time ago - the 4 radials were
arranged at 90 degrees to each other. Yes, those were tuned to
resonance as was the monopole, and they were sloped downward to produce
closer to a 50 ohm match. Those were elevated radials.
With a proper matching network a vertical having the vertical element
and the radial with equal lengths will match in a similar manner to a
center fed dipole, If the radials and the vertical element are not the
same length, then the feed will be similar to an off-center-fed dipole.
(the radial pairs should be of the same length to cancel the horizontal
radiation).
Normally elevated radials are used with resonant vertical sections, and
in that case should be tuned for resonance one at a time with the
vertical section.
73,
Don W3FPR
.
On 7/1/2013 3:49 PM, Ignacy wrote:
Mike WA8BXN wrote
I think elevated radials need to be tuned, that is a particular length for
a
given band. If you will be operating multiple bands, a set is needed for
each band.
If elevated radials are not tuned and not quarter wave, the efficiency may
be even higher than with quarter wave radials but the feed point is likely
to be at a very high voltage. This requires either very high impedance
chokes or transformers. No radial verticals are case in point.
There is a 160m vertical with innovative elevated radial
(http://www.w0uce.net/K2AVantennas.html). It is equivalent to two elevated
radials and coil. There is an anecdotal information that this vertical works
much better than a vertical with many short ground radials.
Ignacy, NO9E
--
View this message in context:
http://elecraft.365791.n2.nabble.com/OT-Radials-for-Vertical-Antenna-tp7576089p7576111.html
Sent from the Elecraft mailing list archive at Nabble.com.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
