Setting aside the mistaken belief that even licensees of several years'
standing
have that a short antenna will radiate all the power that is fed to it, even
long
antennae do not do that!

Consider the terminated and very-directional Rhombic with legs that are
several
wavelengths long; the reason for the termination is to absorb the power that
does not
get radiated and to prevent it being reflected and so making the Rhombic
bi-directional
instead of uni-directional..

Also, consider the following, if shorter (than the Rhombic) antennae radiate
all the
power fed to them, there would be no advantage to extending the length of
any antenna
because the shorter bit would have radiated all the power, and there'd be
nothing left
for the longer bit to radiate.

As it is short (and unterminated) antennae only radiate a small proportion
of the power that
is fed to them, and that which is not radiated is refelcted back to the feed
point considerably
out-of-phase with the incident power and so presenting a very reactive
impedance. (Yes, OK,
on the way back from the reflection, a bit more might get radiated, but I
suspect that the
out-of-phase wave affects the EM fields thereby reducing the radiative
capability)

On 10/26/2014 7:22 AM, gareth wrote:
Setting aside the mistaken belief that even licensees of several
years' standing have that a short antenna will radiate all the power
that is fed to it, even long antennae do not do that!

You are correct. Antennas have some loss as do all things.

Consider the terminated and very-directional Rhombic with legs that
are several wavelengths long; the reason for the termination is to
absorb the power that does not get radiated and to prevent it being
reflected and so making the Rhombic bi-directional instead of
uni-directional..

A rhombic antenna is not a short antenna. It is terminated because it is
designed to be a traveling-wave antenna and not to be a standing-wave
antenna. Please do not compare apples and airplanes.

Also, consider the following, if shorter (than the Rhombic) antennae
radiate all the power fed to them, there would be no advantage to
extending the length of any antenna because the shorter bit would
have radiated all the power, and there'd be nothing left for the
longer bit to radiate.

See my statement above. A rhombic might not radiate all the power fed to
it. As you say, it might be terminated by a resistance. However the
current in the rhombic will cause radiation from the wires with great
efficiency. The purpose of the rhombic is directionality, not efficiency.

As it is short (and unterminated) antennae only radiate a small
proportion of the power that is fed to them, and that which is not
radiated is refelcted back to the feed point considerably
out-of-phase with the incident power and so presenting a very
reactive impedance. (Yes, OK, on the way back from the reflection, a
bit more might get radiated, but I suspect that the out-of-phase wave
affects the EM fields thereby reducing the radiative capability)

The hallmark of a rhombic is that is long compared to the wavelength of
operation in order to achieve directionality (that is, gain in a
particular direction).

If you wish to discuss the difference between standing-wave antennas and
traveling-wave antennas, I would first suggest you learn the difference
between the two so that you can carry on an intelligent dialog.

Was my response to you abusive?

gareth wrote:
Setting aside the mistaken belief that even licensees of several years'
standing
have that a short antenna will radiate all the power that is fed to it, even
long
antennae do not do that!

Ignoring the nonsense about licensees and looking at what physicists have
to say about antennas, we find that all antennas radiate all the power
applied to them minus any resistive loss.

Consider the terminated and very-directional Rhombic with legs that are
several
wavelengths long; the reason for the termination is to absorb the power that
does not
get radiated and to prevent it being reflected and so making the Rhombic
bi-directional
instead of uni-directional..

Also, consider the following, if shorter (than the Rhombic) antennae radiate
all the
power fed to them, there would be no advantage to extending the length of
any antenna
because the shorter bit would have radiated all the power, and there'd be
nothing left
for the longer bit to radiate.

A ridiculous conclusiong that totally ignores both antenna pattern and
the practical issues involved in feeding very short antennas.

As it is short (and unterminated) antennae only radiate a small proportion
of the power that
is fed to them, and that which is not radiated is refelcted back to the feed
point considerably
out-of-phase with the incident power and so presenting a very reactive
impedance. (Yes, OK,
on the way back from the reflection, a bit more might get radiated, but I
suspect that the
out-of-phase wave affects the EM fields thereby reducing the radiative
capability)

All a giant pile of babbling, confused nonsense that shows a total lack
of understanding of how antennas work.



--
Jim Pennino

John S wrote in :

The hallmark of a rhombic is that is long compared to the wavelength of
operation in order to achieve directionality (that is, gain in a
particular direction).


It's totally new to me. I just looked at Google images for a few minutes.
Nice looking constructions. The thing that struck me most was your
description of directionality, non-resonance (at lest, not standing wave),
long compared to wavelength, and termination by a resistance. All these
things can be said of a Bevarage too, but they're obviously very different
too. I don't know what the relation is.

Lostgallifreyan wrote:
John S wrote in :

The hallmark of a rhombic is that is long compared to the wavelength of
operation in order to achieve directionality (that is, gain in a
particular direction).


It's totally new to me. I just looked at Google images for a few minutes.
Nice looking constructions. The thing that struck me most was your
description of directionality, non-resonance (at lest, not standing wave),
long compared to wavelength, and termination by a resistance. All these
things can be said of a Bevarage too, but they're obviously very different
too. I don't know what the relation is.

http://en.wikipedia.org/wiki/Rhombic_antenna

http://www.w8ji.com/rhombic_antennas.htm

A fair antenna is you have a bunch of telephone poles and a huge piece
of empty ground.

Otherwise people these days use log-periodics for better performance
and a lot smaller footprint.


--
Jim Pennino

On 26/10/14 17:44, wrote:
gareth wrote:
Setting aside the mistaken belief that even licensees of several years'
standing
have that a short antenna will radiate all the power that is fed to it, even
long
antennae do not do that!

Ignoring the nonsense about licensees and looking at what physicists have
to say about antennas, we find that all antennas radiate all the power
applied to them minus any resistive loss.

Which is exactly what was posted by those who posted correct inputs said.

As usual, Evans is posting malicious nonsense.


Consider the terminated and very-directional Rhombic with legs that are
several
wavelengths long; the reason for the termination is to absorb the power that
does not
get radiated and to prevent it being reflected and so making the Rhombic
bi-directional
instead of uni-directional..

Also, consider the following, if shorter (than the Rhombic) antennae radiate
all the
power fed to them, there would be no advantage to extending the length of
any antenna
because the shorter bit would have radiated all the power, and there'd be
nothing left
for the longer bit to radiate.

A ridiculous conclusiong that totally ignores both antenna pattern and
the practical issues involved in feeding very short antennas.

He lacks even a grasp of the most basic antenna theory.


As it is short (and unterminated) antennae only radiate a small proportion
of the power that
is fed to them, and that which is not radiated is refelcted back to the feed
point considerably
out-of-phase with the incident power and so presenting a very reactive
impedance. (Yes, OK,
on the way back from the reflection, a bit more might get radiated, but I
suspect that the
out-of-phase wave affects the EM fields thereby reducing the radiative
capability)

All a giant pile of babbling, confused nonsense that shows a total lack
of understanding of how antennas work.


One of his standard ploys is to utter a load of such techno-nonsense.
Another is to hurl abuse. He has less pleasant ploys which, hopefully,
you will be spared.

In article ,
Lostgallifreyan wrote:

It's totally new to me. I just looked at Google images for a few minutes.
Nice looking constructions. The thing that struck me most was your
description of directionality, non-resonance (at lest, not standing wave),
long compared to wavelength, and termination by a resistance. All these
things can be said of a Bevarage too, but they're obviously very different
too. I don't know what the relation is.

There's a nice discussion of various traveling-wave antennas in
Laporte's classic "Radio Antenna Engineering" text.

http://snulbug.mtview.ca.us/books/Ra...naEngineering/

"Brian Reay" wrote in message
...
As usual, Evans is posting malicious nonsense.

Once again, you post gratuitous abuse but without venturing a technical
contribution yourself


He lacks even a grasp of the most basic antenna theory.

Once again, you post gratuitous abuse

One of his standard ploys is to utter a load of such techno-nonsense.
Another is to hurl abuse. He has less pleasant ploys which, hopefully, you
will be spared.

Once again, you post gratuitous abuse

So, M3OSN, are you having a hard time this weekend which has resulted in you
lashing out in all directions in every NG that you frequent?

"Brian Reay" wrote in message
...

He has less pleasant ploys which, hopefully, you will be spared.

Are you, perhaps, referring to the precedent that you set in 2005 to
threaten
the liberties and livelihoods of those who did no more than to openly
disagree with you
on Usenet by sending for them to be arrested by the ploddery?

Did it not occur to you that your victims could end up getting the sack from
their jobs when you did that?

En el artículo , John S
escribió:

Was my response to you abusive?

He won't have liked it, ergo, yes.

--
(\_/)
(='.'=)
(")_(")