Everything you want to know about antennae ....
 

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

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

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

Everything you want to know about antennae ....
 

"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 :-)

Everything you want to know about antennae ....
 

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

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

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

Everything you want to know about antennae ....
 

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

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

In rec.radio.amateur.antenna gareth G4SDW GQRP #3339 wrote:
"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.

I make all my short antennas out of superconductors so they do not have
ohmic resistance.

--
Jim Pennino

Everything you want to know about antennae ....
 

"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

Everything you want to know about antennae ....
 

"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.

Everything you want to know about antennae ....
 

On 02/24/2016 12:19 AM, 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 all depends on the length of the antenna against the operating
frequency .
A half wave vertical has a high RF voltage at its "bottom" but a low RF
current at that point ,hence less ground loss ,meaning that not all that
many radials are required compared with a quarter wave vertical .
Of course an impedance transformer is required .
A well known transformer is an inductor of 14 windings between ground
and vertical antenna and over it one of 2 windings connected to the
feeder and hence transmitter ,resulting in a 1:7 voltage transformation
,hence a 1: 49 (say 50) impedance transformation . Across the 14
windings is a HV variable capacitor to adjust for minimal SWR.

A well known matching circuit (tuner if you wish) used for low power HF
ARDF transmitters is the L-circuit by G3ZOI
Here the low impedance of the transmitter's output is in series with a
variable capacitor the other side connected to the(high impedance) short
wire antenna and to a grounded inductor . With 2 diodes in series with a
LED in de output to the antenna the LED is adjusted for max RF current
(max LED brightness). For 1-5 W transmitters the variable capacitor can
be a polyvarcon type from a portable MW receiver ....works very well !

Frank GM0CSZ / KN6WH in IO87AT

Everything you want to know about antennae ....
 

On 2/29/2016 1:42 PM, gareth G4SDW GQRP #3339 wrote:
"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.

All practical antenna have ohmic resistance. None are perfectly
efficient. You can design any antenna to have any efficiency you wish
by using suitable materials even if you have to use superconductors.

--

Rick

Everything you want to know about antennae ....
 

"rickman" wrote in message ...

On 2/29/2016 1:42 PM, gareth G4SDW GQRP #3339 wrote:
"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.

# All practical antenna have ohmic resistance. None are perfectly
# efficient. You can design any antenna to have any efficiency you wish
# by using suitable materials even if you have to use superconductors.

I gave up. If we are talking about theoretical antennas, they are lossless.

Everything you want to know about antennae ....
 

In rec.radio.amateur.antenna Wayne wrote:


"rickman" wrote in message ...

On 2/29/2016 1:42 PM, gareth G4SDW GQRP #3339 wrote:
"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.

# All practical antenna have ohmic resistance. None are perfectly
# efficient. You can design any antenna to have any efficiency you wish
# by using suitable materials even if you have to use superconductors.

I gave up. If we are talking about theoretical antennas, they are lossless.

Theoretical antennas have whatever loss you assign to them.


--
Jim Pennino

Everything you want to know about antennae ....
 

wrote in message ...

In rec.radio.amateur.antenna Wayne wrote:


"rickman" wrote in message ...

On 2/29/2016 1:42 PM, gareth G4SDW GQRP #3339 wrote:
"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.

# All practical antenna have ohmic resistance. None are perfectly
# efficient. You can design any antenna to have any efficiency you wish
# by using suitable materials even if you have to use superconductors.

I gave up. If we are talking about theoretical antennas, they are
lossless.

# Theoretical antennas have whatever loss you assign to them.

And lossless is a good way to get down to basics.