Forgiving their ignorant use of the wrong plural, "antennas", this is a
brilliant site, at first sight ...

http://antenna-theory.com/


In particular, the following sub-page may teach the Yank rednecks
who abuse this NG a thing or two ...


http://www.antenna-theory.com/antennas/shortdipole.php

"gareth" wrote in message ...

Forgiving their ignorant use of the wrong plural, "antennas", this is a
brilliant site, at first sight ...

http://antenna-theory.com/


In particular, the following sub-page may teach the Yank rednecks
who abuse this NG a thing or two ...


http://www.antenna-theory.com/antennas/shortdipole.php

Good references, but I see nothing new in the second reference with regard
to short dipoles.

If you can get 100 watts into a one foot long HF dipole, it will be just as
efficient as a half wave dipole that also has 100 watts into it.

Wayne wrote:

"gareth" wrote in message ...

Forgiving their ignorant use of the wrong plural, "antennas", this is a
brilliant site, at first sight ...

http://antenna-theory.com/


In particular, the following sub-page may teach the Yank rednecks
who abuse this NG a thing or two ...


http://www.antenna-theory.com/antennas/shortdipole.php

Good references, but I see nothing new in the second reference with regard
to short dipoles.

If you can get 100 watts into a one foot long HF dipole, it will be just as
efficient as a half wave dipole that also has 100 watts into it.

Agreed. It is a good summary. It confirms what many of us have said,
that there is nothing special about a small antenna that makes it
inefficient except that it has an inconvenient reactive impedance and a
low radiation resistance. Given a theoretical lossless matching network
(which would be impossible to realise in practice) the one in the
example could be 99% efficient, as the loss resistance of the actual
antenna is only about 1% of the radiation restistance.

If Gareth now agrees with this analysis we are now in the happy position
of all agreeing.

--

Roger Hayter

"Wayne" wrote in message
...
If you can get 100 watts into a one foot long HF dipole, it will be just
as efficient as a half wave dipole that also has 100 watts into it.

But only on the very narrow band that your lossless matching covers.
If you want the bandwidth of an halfwave dipole you will need
a lot of one foot ones plus a lossless distribution filter.
Very far form "as efficient" IMHO
And on receive the things get worse :-)

bilou wrote:

"Wayne" wrote in message
...
If you can get 100 watts into a one foot long HF dipole, it will be just
as efficient as a half wave dipole that also has 100 watts into it.

But only on the very narrow band that your lossless matching covers.
If you want the bandwidth of an halfwave dipole you will need
a lot of one foot ones plus a lossless distribution filter.
Very far form "as efficient" IMHO
And on receive the things get worse :-)

I don't think anyone disputes that it would be a hopeless antenna
*system*. The point being that the antenna itself is not particularly
inefficient in the technical sense, just very inconvenient to feed. And
that was the original point in dispute.



--

Roger Hayter

"Roger Hayter" wrote in message
...

bilou wrote:

"Wayne" wrote in message
...
If you can get 100 watts into a one foot long HF dipole, it will be just
as efficient as a half wave dipole that also has 100 watts into it.

But only on the very narrow band that your lossless matching covers.
If you want the bandwidth of an halfwave dipole you will need
a lot of one foot ones plus a lossless distribution filter.
Very far form "as efficient" IMHO
And on receive the things get worse :-)

# I don't think anyone disputes that it would be a hopeless antenna
# *system*. The point being that the antenna itself is not particularly
# inefficient in the technical sense, just very inconvenient to feed. And
# that was the original point in dispute.

Dead on explanation. Some have insisted that inefficiencies result from
antenna size and not from matching challenges.

"Wayne" wrote

Dead on explanation. Some have insisted that inefficiencies
result from antenna size and not from matching challenges.
_______

Kindly note that the radiation efficiency of an antenna _system_ is related
to its radiation resistance compared to other resistive losses present in
that antenna system.

It is possible to perfectly match the impedance at the feedpoint of an
antenna system to the impedance of the transmission line connected there.
But that antenna system still can have very poor radiation efficiency at
that frequency.

An example of this is a Z-matched, but electrically short vertical monopole
driven against a poor r-f ground connection such as a few buried ground
rods. Most of the available transmitter power is dissipated in the r-f
ground resistance, rather than being usefully radiated as e-m waves.