wrote:
I have searched quite a bit for evidence that states that performance
of antennas can be rated by it's size. Formulas do not refere to
radiator size or volume
and aparture is referenced to gain. I understand that sort of thinking
based on Yagi design
but the idea that all small radiators are inefficient is rather
ludicrouse. My work, based on
the sciences of the masters, show that a efficient radiator can be any
size,shape and
configuration as long as it
is in equilibrium . Period
No where can I find reference to "size" in what the masters state
Regards
Art

The work by Chu (Journal of Applied Physics, p1163, v19, Dec 1948) and
subsequently by Harrington (IEEE Trans Ant & Prop, V18#6, Nov 1965,
p896) , Thiele (IEEE Trans on Ant and Prop, v51, #6, June 2003, p1263)
and later others, discusses fundamental limits on performance. Watch
out, though, for the assumptions in the constraints (e.g. whether the
device attached to the feedpoint is reciprocal), and, of course, where
the boundary of the system is.

Watch out also for the definition of "Q", which in this context is the
ratio of stored to disspated/radiated energy, not the ratio of center
frequency/bandwidth.


In short, there is a tradeoff between Q, directivity, and size. And,
because high Q implies high stored energy, for physically realizable
antennas with loss, efficiency is in the mix too.





Googling "chu harrington limit" often turns up useful stuff.

On Mar 7, 11:46 am, Jim Lux wrote:
wrote:
I have searched quite a bit for evidence that states that performance
of antennas can be rated by it's size. Formulas do not refere to
radiator size or volume
and aparture is referenced to gain. I understand that sort of thinking
based on Yagi design
but the idea that all small radiators are inefficient is rather
ludicrouse. My work, based on
the sciences of the masters, show that a efficient radiator can be any
size,shape and
configuration as long as it
is in equilibrium . Period
No where can I find reference to "size" in what the masters state
Regards
Art

The work by Chu (Journal of Applied Physics, p1163, v19, Dec 1948) and
subsequently by Harrington (IEEE Trans Ant & Prop, V18#6, Nov 1965,
p896) , Thiele (IEEE Trans on Ant and Prop, v51, #6, June 2003, p1263)
and later others, discusses fundamental limits on performance. Watch
out, though, for the assumptions in the constraints (e.g. whether the
device attached to the feedpoint is reciprocal), and, of course, where
the boundary of the system is.

Watch out also for the definition of "Q", which in this context is the
ratio of stored to disspated/radiated energy, not the ratio of center
frequency/bandwidth.

In short, there is a tradeoff between Q, directivity, and size. And,
because high Q implies high stored energy, for physically realizable
antennas with loss, efficiency is in the mix too.

Googling "chu harrington limit" often turns up useful stuff.

Googled Chu harrington and find that his work is basically empirical
around known arrangements.
When he brought the question of Q into the picture he made the
statement that small antennas
are usually of a low impedance which is correct empirically with
respect to existing designs but it is not exclusive
when dealing with all radiators that can be made that comply with
Maxwells laws. As I have said before it is implicite in Maxwells laws
that a efficient radiator can be any size shape or configuration as
long as it complies with Maxwells law.
In my case my small antenna can have any impedance value for
equilibrium and it is quite easy to have a resistive impedance in the
hundreds of ohms as well as minuit impedances. I conform to 50 ohms
purely because of component availability. As another aside my small
antennas
have a much wider bandwidth than any other available! As far as gain
or energy transmitted that all depends on what frequencies get thru
the bandpass filter and in no way directs out of pass energy to be be
redirected to band pass status and augment energy transmitted. Stored
energy has no relationship to Q in my mind since it goes around or
circulates as with a tank circuit energy that lies within the pass
bandof the tank circuit filter.
To summate, my antenna design is considered small yet complies with
Maxwells laws and yet does not have a narrow bandwidth or low
impedance thus Chu's comments cannot be inclusive of all radiators.
Best regards
Art

On Mar 7, 7:29 pm, Art Unwin wrote:

When he brought the question of Q into the picture he made the
statement that small antennas
are usually of a low impedance which is correct empirically with
respect to existing designs but it is not exclusive
when dealing with all radiators that can be made that comply with
Maxwells laws.

I take it your version is gifted and suffers not from a low Q... :/

As I have said before it is implicite in Maxwells laws
that a efficient radiator can be any size shape or configuration as
long as it complies with Maxwells law.

Sure it can. Common knowledge. It's also common knowledge
that the trick with building a small efficient antenna is not really
the size of the radiator itself, it's actually getting power to that
small radiator.


In my case my small antenna can have any impedance value for
equilibrium and it is quite easy to have a resistive impedance in the
hundreds of ohms as well as minuit impedances. I conform to 50 ohms
purely because of component availability. As another aside my small
antennas
have a much wider bandwidth than any other available!

As previously noted, you have reinvented the air cooled dummy
load. Your performance specs sure seem to mimic one anyway.. :/

As far as gain
or energy transmitted that all depends on what frequencies get thru
the bandpass filter and in no way directs out of pass energy to be be
redirected to band pass status and augment energy transmitted. Stored
energy has no relationship to Q in my mind since it goes around or
circulates as with a tank circuit energy that lies within the pass
bandof the tank circuit filter.
To summate, my antenna design is considered small yet complies with
Maxwells laws and yet does not have a narrow bandwidth or low
impedance thus Chu's comments cannot be inclusive of all radiators.
Best regards
Art

As far as the rest, my cat has mittens.. :/
BTW, you need to define "equilibrium".
After several months you still are lagging at this task.
MK

Art Unwin wrote:
On Mar 7, 11:46 am, Jim Lux wrote:

wrote:

I have searched quite a bit for evidence that states that performance
of antennas can be rated by it's size. Formulas do not refere to
radiator size or volume
and aparture is referenced to gain. I understand that sort of thinking
based on Yagi design
but the idea that all small radiators are inefficient is rather
ludicrouse. My work, based on
the sciences of the masters, show that a efficient radiator can be any
size,shape and
configuration as long as it
is in equilibrium . Period
No where can I find reference to "size" in what the masters state
Regards
Art

The work by Chu (Journal of Applied Physics, p1163, v19, Dec 1948) and
subsequently by Harrington (IEEE Trans Ant & Prop, V18#6, Nov 1965,
p896) , Thiele (IEEE Trans on Ant and Prop, v51, #6, June 2003, p1263)
and later others, discusses fundamental limits on performance. Watch
out, though, for the assumptions in the constraints (e.g. whether the
device attached to the feedpoint is reciprocal), and, of course, where
the boundary of the system is.

Watch out also for the definition of "Q", which in this context is the
ratio of stored to disspated/radiated energy, not the ratio of center
frequency/bandwidth.

In short, there is a tradeoff between Q, directivity, and size. And,
because high Q implies high stored energy, for physically realizable
antennas with loss, efficiency is in the mix too.

Googling "chu harrington limit" often turns up useful stuff.


Googled Chu harrington and find that his work is basically empirical
around known arrangements.
When he brought the question of Q into the picture he made the
statement that small antennas
are usually of a low impedance which is correct empirically with
respect to existing designs but it is not exclusive

To summate, my antenna design is considered small yet complies with
Maxwells laws and yet does not have a narrow bandwidth or low
impedance thus Chu's comments cannot be inclusive of all radiators.
Best regards
Art

which is why I mentioned:
"Watch out, though, for the assumptions in the constraints"

However, I believe it is incorrect to characterize his analysis as
empiricism (i.e. getting experimental data and fitting curves). His
analysis (and that of Harrington and Thiele) is entirely theoretical,
and actually doesn't deal with loss in the antenna, per se. Indeed,
Chu's analysis is based on a simple case (a dipole), but that's more
because it's a good first example (and he could use the previous work of
Schelkunoff as a starting point). I believe the analysis is generally
valid, regardless of what the actual antenna is.

On Mar 10, 11:19 am, Jim Lux wrote:
Art Unwin wrote:
On Mar 7, 11:46 am, Jim Lux wrote:

wrote:

I have searched quite a bit for evidence that states that performance
of antennas can be rated by it's size. Formulas do not refere to
radiator size or volume
and aparture is referenced to gain. I understand that sort of thinking
based on Yagi design
but the idea that all small radiators are inefficient is rather
ludicrouse. My work, based on
the sciences of the masters, show that a efficient radiator can be any
size,shape and
configuration as long as it
is in equilibrium . Period
No where can I find reference to "size" in what the masters state
Regards
Art

The work by Chu (Journal of Applied Physics, p1163, v19, Dec 1948) and
subsequently by Harrington (IEEE Trans Ant & Prop, V18#6, Nov 1965,
p896) , Thiele (IEEE Trans on Ant and Prop, v51, #6, June 2003, p1263)
and later others, discusses fundamental limits on performance. Watch
out, though, for the assumptions in the constraints (e.g. whether the
device attached to the feedpoint is reciprocal), and, of course, where
the boundary of the system is.

Watch out also for the definition of "Q", which in this context is the
ratio of stored to disspated/radiated energy, not the ratio of center
frequency/bandwidth.

In short, there is a tradeoff between Q, directivity, and size. And,
because high Q implies high stored energy, for physically realizable
antennas with loss, efficiency is in the mix too.

Googling "chu harrington limit" often turns up useful stuff.

Googled Chu harrington and find that his work is basically empirical
around known arrangements.
When he brought the question of Q into the picture he made the
statement that small antennas
are usually of a low impedance which is correct empirically with
respect to existing designs but it is not exclusive
To summate, my antenna design is considered small yet complies with
Maxwells laws and yet does not have a narrow bandwidth or low
impedance thus Chu's comments cannot be inclusive of all radiators.
Best regards
Art

which is why I mentioned:
"Watch out, though, for the assumptions in the constraints"

However, I believe it is incorrect to characterize his analysis as
empiricism (i.e. getting experimental data and fitting curves). His
analysis (and that of Harrington and Thiele) is entirely theoretical,
and actually doesn't deal with loss in the antenna, per se. Indeed,
Chu's analysis is based on a simple case (a dipole), but that's more
because it's a good first example (and he could use the previous work of
Schelkunoff as a starting point). I believe the analysis is generally
valid, regardless of what the actual antenna is.

You may well be correct. I cannot enter the IEEE papers that you
allude to
to study it furthur. The fact that my impedences are high and the
bandwith is large
is really putting me in a unknown area and I have a lot to learn about
it
Regards
Art

You can pretty much sum up the characteristics of small antennas as:

Small - Broadband - Efficient: Pick any two.

Roy Lewallen, W7EL

On Mar 10, 1:56 pm, Roy Lewallen wrote:
You can pretty much sum up the characteristics of small antennas as:

Small - Broadband - Efficient: Pick any two.

Roy Lewallen, W7EL

Who knows what "efficiency" represents in the electrical world?
It is the word "small" that confuses everybody when the word
should be" fractional wavelength".
Small and large are meaningles in the antenna world.
No I diddn't overlook the sniping.

Art Unwin wrote:
On Mar 10, 1:56 pm, Roy Lewallen wrote:

You can pretty much sum up the characteristics of small antennas as:

Small - Broadband - Efficient: Pick any two.

Roy Lewallen, W7EL


Who knows what "efficiency" represents in the electrical world?

I think the conventional meaning would be power radiated vs power into
the system.

If you define "power radiated" to mean "power radiated in a particular
direction" then you're adding directivity into the mix.

If you define "power into the system" to be 120V Wall power that's
different than RF power at the feedpoint of the antenna which is
different than RF power out at the output of the transmitter.

So, you have to define the appropriate reference plane. The antenna
literature tends to draw the boundary at the feedpoint of the antenna,
because the rest is "circuit theory".

The ham world tends to draw the boundary at the output of the
transmitter (so we include loss in feedlines and matching networks),
because the FCC power limit is usually measured at that point. (although
nothing in the rules says you can't measure after the matching network)

In the commercial broadcast world, there's a sort of hybrid, because
there's an RF power limit AND a requirement to have a particular field
strength in the far field at a particular distance.



It is the word "small" that confuses everybody when the word
should be" fractional wavelength".


Nope.. small in an absolute sense. An antenna that is 10 times bigger
will have more directivity or other figure of merit. Applies pretty
much whether you're comparing an antenna that is 0.01 wavelength to 0.1
or comparing one that is 10 wavelengths to one that is 100 wavelengths.

What you can't say is that the amount of change from 0.01 to 0.1 is the
same as from 10 to 100.

Small and large are meaningles in the antenna world.

They have meaning as far as relative. large is better than small.
And, "directive" antennas that are small relative to a wavelength tend
to have high Q (in the stored vs radiated energy sense, which may or may
not imply narrow bandwidth)


It's probably worth finding a library that can get you copies of the
papers, rather than relying on interpretations and summaries. The most
common misinterpretation is to conceptually equate antenna Q to antenna
bandwidth.

No I diddn't overlook the sniping.