In article
,
Art Unwin wrote:

On Aug 3, 5:24*am, Richard Fry wrote:
On Aug 2, 3:01*pm, Art Unwin wrote:

An end fed antenna cannot be of a fractional wavelength...

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? ?

Art, note that the vertical monopoles used by MW broadcast stations
are ALL fractional-wavelength radiators, and probably 99% of them are
end fed.

I regard a radiator with a counterpoise as being center fed of a
given impedance to connect to regardles whether the counterpoise is
above ground or not. If a radiator is of a closed cuircuit form it may
be fed at any point in physical terms. Other peoples definitions may
vary. The poster I understood to be at the position of the end of a
transmission line with two wires in hand and wanted advice from that
point to procede. If his advisers are going to quibble then he needs
to go elsewhere for advise or settle for a poll.

All this discussion of "counterpoise" should be centered around Single
Frequency Antenna Systems Design, and is NOT relative to multi-Band, or
Wider than 10% of Frequency, Bandwidth, End Feed Antenna Designs. These
latter Antenna Systems are not using a Counterpoise, as such, but REQUIRE
a LOW Impedance BroadBand RF Ground, which in most cases needs to be
built, on site, and engineered to provide that Low Impedance, Wide Band
RF Characteristics for the specific Radio System. Having spent a career
designing, installing, and operating LF/MF/HF Communications Stations,
all over the world, it isn't a trivial undertaking, should one actually
want the best Antenna System, possible, for any one location. There are
MANY factors to consider, with Ground Conductivity, Water Depth, changes
of these during the passing seasons, and Frequencies and Bands chosen
for communication links. In many cases an End Feed Vertical, just isn't
the best Antenna System for the location. In other cases, they can be
designed for really good efficiency and great propagation. On of the
best Systems I ever installed was a 70' insolated Tower, with a SEA-330
AutoTuner tied to the center of a 100 Sq Ft Galvinized Screen built in
the center of a One Sq. Mile Salt Marsh, that flooded every 12 hours on
High Tide. Rf Impedance was below 5 Ohms from 200 Khz, clear up thru 22
Mhz.

--
Bruce in alaska
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