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.

Richard Fry wrote:

"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.

That is true. But the statement you were responding to was made in
response to a specific example where the RF loss resistance was much
smaller than the 0.49.ohm radation resistance. And the whole
discussion arose from the suggestion that short antennas are
*necessarily* inefficient because they cannot radiate without loss.
Your example is a good one of a system with a large loss resistance
which needs a higher radiation resistance monopole to feed the
combination efficiently in series. It is a perfectly good example, but
shows nothing about the intriinsic radiation efficiency of a short
antenna, just about its practical usefulness in a certain situations.


--

Roger Hayter

In rec.radio.amateur.antenna Richard Fry wrote:
"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.

And the poor ground is not part of the antenna system?



--
Jim Pennino

"Richard Fry" wrote in message ...

"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.

Duly noted, but the technical point I addressed was a bit different from the
antenna system you describe.

There has previously on the newsgroup been a claim that shortness makes
inefficiency.
To that I say that if for example, 100 watts is fed to a resonant HF dipole,
and 100 watts is fed to a 1 foot long dipole, both radiate 100 watts.
Different patterns, but the power radiated is the same, if you manage to
successfully get the power to the antenna.

"Wayne" wrote in message
...

There has previously on the newsgroup been a claim that shortness makes
inefficiency.
To that I say that if for example, 100 watts is fed to a resonant HF
dipole, and 100 watts is fed to a 1 foot long dipole, both radiate 100
watts.
Different patterns, but the power radiated is the same, if you manage to
successfully get the power to the antenna.

The ratio of radiation resistance to ohmic resistance will give the lie to
your claim.

"gareth G4SDW GQRP #3339" wrote in message
...

"Wayne" wrote in message
...

There has previously on the newsgroup been a claim that shortness makes
inefficiency.
To that I say that if for example, 100 watts is fed to a resonant HF
dipole, and 100 watts is fed to a 1 foot long dipole, both radiate 100
watts.
Different patterns, but the power radiated is the same, if you manage to
successfully get the power to the antenna.

The ratio of radiation resistance to ohmic resistance will give the lie to
your claim.

In my claim, equal power arrives at the long or short antenna AFTER the
ohmic resistances have already occurred.

Doesn't matter if you need 2000 watts to deliver 100 watts to the short
antenna.

My understanding is that you claim the short antenna is inefficient only
because it is short.

"Wayne" wrote:
"gareth G4SDW GQRP #3339" wrote in message ...

"Wayne" wrote in message
...

There has previously on the newsgroup been a claim that shortness makes inefficiency.
To that I say that if for example, 100 watts is fed to a resonant HF
dipole, and 100 watts is fed to a 1 foot long dipole, both radiate 100 watts.
Different patterns, but the power radiated is the same, if you manage
to successfully get the power to the antenna.

The ratio of radiation resistance to ohmic resistance will give the lie to your claim.

In my claim, equal power arrives at the long or short antenna AFTER the
ohmic resistances have already occurred.

Doesn't matter if you need 2000 watts to deliver 100 watts to the short antenna.

My understanding is that you claim the short antenna is inefficient only
because it is short.

Wayne, you're wasting your breath. You'll never get Gareth to see sense on
this. He's been banging this drum for years now.


--
STC // M0TEY // twitter.com/ukradioamateur

"Wayne" wrote in message
...
"gareth G4SDW GQRP #3339" wrote in message
...
"Wayne" wrote in message
...
There has previously on the newsgroup been a claim that shortness makes
inefficiency.
To that I say that if for example, 100 watts is fed to a resonant HF
dipole, and 100 watts is fed to a 1 foot long dipole, both radiate 100
watts.
Different patterns, but the power radiated is the same, if you manage to
successfully get the power to the antenna.

The ratio of radiation resistance to ohmic resistance will give the lie to
your claim.

In my claim, equal power arrives at the long or short antenna AFTER the
ohmic resistances have already occurred.

I don't know what you mean by that. The Ohmic resistances to which I
referred
were those of the antenna rod itself.