But, if the "wonder antenna" is small enough to be enclosed (mostly) in
something transparent to the RF but not to the thermal thats generated by
any I^2* R losses, wouldnt the temperture rise inside the enclosure give a
decent indication of efficiency?



No need for that really, too cumbersome. If you measure R you can calculate
losses due to dissipation in heat.

Again, real comparison of efficiency of shortened antenna is to compare against
the same pattern producing full (electrical) length antenna, everything is
included in what you would measure. Much simpler too. I can build quarter wave
vertical faster than styrofoam igloo. :-)

Basic rules are, best inductive loading is about 2/3 up the radiator, coil is
better than loading stub, top hat is the best. Anything else is jocker's
attempt at perpetuum mobile.

Yuri

Yuri

I sure disagree about being able to determine an antenna's efficiency by
either resistance measurements or by measuring received signa;l strength at
any one point in space. But, you are certainly a much smarter fuy than I
ever was. So, I am not equipped to get into a news group contest.
It is my contention that the antenna under test's complete radiation
pattern and field strength would have to be measured and integrated if
field strength is used to determine it's efficiency. That could get
coplicated.
It would have seemed to me that the loss in any "R" is dependent on the
current flowing in it. And, I'd be concerned that any resonances could have
higher circulating currents at the operating frequency.

If you can point out the errors in my convictions, I'd like to read about
where I'm wrong.

Jerry




"Yuri Blanarovich" wrote in message
...
But, if the "wonder antenna" is small enough to be enclosed (mostly) in
something transparent to the RF but not to the thermal thats generated by
any I^2* R losses, wouldnt the temperture rise inside the enclosure give
a
decent indication of efficiency?



No need for that really, too cumbersome. If you measure R you can
calculate
losses due to dissipation in heat.

Again, real comparison of efficiency of shortened antenna is to compare
against
the same pattern producing full (electrical) length antenna, everything is
included in what you would measure. Much simpler too. I can build quarter
wave
vertical faster than styrofoam igloo. :-)

Basic rules are, best inductive loading is about 2/3 up the radiator, coil
is
better than loading stub, top hat is the best. Anything else is jocker's
attempt at perpetuum mobile.

Yuri

I sure disagree about being able to determine an antenna's efficiency by
either resistance measurements or by measuring received signa;l strength at
any one point in space.

From practical, engineer's point of view, and we are looking at shortened
(loaded) antennas, you (or at least I) want to know how efficient the loaded
antenna is vs. equivalent (same pattern producing) antenna. You want to compare
oranges with oranges. The ultimate indicator is how much is one better (worst)
than the other producing more (less) transmit (or receive) signal. That is the
ultimate parameter that we are looking for, that's what you want to measure and
compare. We have dB as a unit for that. 3dB means you gain (lose) double
(power) signal. If you lose 50% in the heat, you will see corresponding loss in
signal strength. So forget the igloo!


But, you are certainly a much smarter fuy than I
ever was. So, I am not equipped to get into a news group contest.

How did you arrive at that without putting me in the styrofoam igloo, or that I
am Fuy? :-)

It is my contention that the antenna under test's complete radiation
pattern and field strength would have to be measured and integrated if
field strength is used to determine it's efficiency. That could get
coplicated.

NOT! That's why you want to use the same pattern producing antennas for
comparison (apples to apples) i.e. quarter wave (electrical) shortened (loaded)
vertical vs. full size quarter wave vertical made of same material (tubing).
You can make measurements at the same point (properly chosen) and compare
signal levels while swapping the antennas at the same test site.

It would have seemed to me that the loss in any "R" is dependent on the
current flowing in it. And, I'd be concerned that any resonances could have
higher circulating currents at the operating frequency.


Circulating in what?

If you can point out the errors in my convictions, I'd like to read about
where I'm wrong.


You can be "convicted" in anything you like. But you have to look at the
problems and see what are you trying to achieve. I always try to make antenna
to produce the maximum signal in the desired direction, pattern. That's what
you try to measure, evaluate. Anything else is just contributing factor that
gets included in the final parameter - signal strength. You can fart with heat,
resistances, etc., I do not use antennas for heating, I use them for producing
or extracting signals and that's what I am interested in and want to quantify.
You need proper "standard" and use proper parameters to compare your "miracle"
against.

If Mr. Vincent "discovers" that his shortened antenna is more broadband than
full size (same electrical length) radiator, than he has some serious resistors
"broadening" the response. My dummy load is perfect broadband "antenna" and
almost 100% "efficient" - turns almost 100% of power into a heat, but radiates
almost nothing.

The point is, you can measure other things like heat generated by the loses,
but you are neglecting other parameters that come to play, leading you astray,
while neglecting the most important parameter - the result you are (or I am)
after - the signal strength!
Does that "convict" you? Otherwise I rest my case.
Jerry


Yuri, K3BU.us

Yuri

I realize you are a smart and important guy who knows alot about
electronucs. But, when you enter in a thread at this time with statements
about defining "3 DB" I wonder if you think everyone else is supid except
you. Whats the point of defining "3DB??
I used to work with some very good engineers who happened to think
measuring measuring antenna heating was a fairly decent way of getting
"loss" data on an antenna. I happen to think it is a good way to get some
preliminary info on antenna loss.
So, when you tell me to "forget the igloo", you seem to have placed
yourself in a position where you think you know how to evaluate antenna
efficiency and that I dont. I dont think you are *that* smart.

Jerry


"Yuri Blanarovich" wrote in message
...

I sure disagree about being able to determine an antenna's efficiency
by
either resistance measurements or by measuring received signa;l strength
at
any one point in space.

From practical, engineer's point of view, and we are looking at shortened
(loaded) antennas, you (or at least I) want to know how efficient the
loaded
antenna is vs. equivalent (same pattern producing) antenna. You want to
compare
oranges with oranges. The ultimate indicator is how much is one better
(worst)
than the other producing more (less) transmit (or receive) signal. That is
the
ultimate parameter that we are looking for, that's what you want to
measure and
compare. We have dB as a unit for that. 3dB means you gain (lose) double
(power) signal. If you lose 50% in the heat, you will see corresponding
loss in
signal strength. So forget the igloo!


But, you are certainly a much smarter fuy than I
ever was. So, I am not equipped to get into a news group contest.

How did you arrive at that without putting me in the styrofoam igloo, or
that I
am Fuy? :-)

It is my contention that the antenna under test's complete radiation
pattern and field strength would have to be measured and integrated if
field strength is used to determine it's efficiency. That could get
coplicated.

NOT! That's why you want to use the same pattern producing antennas for
comparison (apples to apples) i.e. quarter wave (electrical) shortened
(loaded)
vertical vs. full size quarter wave vertical made of same material
(tubing).
You can make measurements at the same point (properly chosen) and compare
signal levels while swapping the antennas at the same test site.

It would have seemed to me that the loss in any "R" is dependent on the
current flowing in it. And, I'd be concerned that any resonances could
have
higher circulating currents at the operating frequency.


Circulating in what?

If you can point out the errors in my convictions, I'd like to read
about
where I'm wrong.


You can be "convicted" in anything you like. But you have to look at the
problems and see what are you trying to achieve. I always try to make
antenna
to produce the maximum signal in the desired direction, pattern. That's
what
you try to measure, evaluate. Anything else is just contributing factor
that
gets included in the final parameter - signal strength. You can fart with
heat,
resistances, etc., I do not use antennas for heating, I use them for
producing
or extracting signals and that's what I am interested in and want to
quantify.
You need proper "standard" and use proper parameters to compare your
"miracle"
against.

If Mr. Vincent "discovers" that his shortened antenna is more broadband
than
full size (same electrical length) radiator, than he has some serious
resistors
"broadening" the response. My dummy load is perfect broadband "antenna"
and
almost 100% "efficient" - turns almost 100% of power into a heat, but
radiates
almost nothing.

The point is, you can measure other things like heat generated by the
loses,
but you are neglecting other parameters that come to play, leading you
astray,
while neglecting the most important parameter - the result you are (or I
am)
after - the signal strength!
Does that "convict" you? Otherwise I rest my case.
Jerry


Yuri, K3BU.us

So, when you tell me to "forget the igloo", you seem to have placed
yourself in a position where you think you know how to evaluate antenna
efficiency and that I dont. I dont think you are *that* smart.

Jerry


You win, I ain't so smart as I thought. :-)
I thought that antenna is supposed to radiate RF in the direction and with
pattern one desires. That's what I want to measure, how effective radiator it
is, how much RF it produces at the point of interest.
If you want to know how well it works as a heater, more power to you.
I am not in a ****ing contest who is "smarter", I was trying to convey some
practicality and what I do and what I am interested in.
Over and out!

Back to DR1 (www.computeradio.us)

Yuri, K3BU

On 17 Aug 2004 11:12:46 GMT, oUsama (Yuri Blanarovich)
wrote:

I thought that antenna is supposed to radiate RF in the direction and with
pattern one desires. That's what I want to measure, how effective radiator it
is, how much RF it produces at the point of interest.

Of course that is what everyone would want to measure, but unless you
are working in the millimeter bands in a non-echoic chamber,
determining the true (absolute) radiation pattern can be quite
problematic.

You could fly around in a plane with a calibrated field strength meter
in trying to determine the true radiation pattern of the antenna.
However, the variations in ground conductivity may create a large
variations if the measurement is repeated at different places,
especially with unbalanced antennas.

Thus, it would help a lot, if the efficiency could be determined
separately from the radiation pattern, since much of the calibration
problems could be eliminated. The calorimetric method of measuring the
heat dissipated by the losses is one usable method to get the
efficiency.

If some manufacturer claims extraordinary _gain_ figures for some
LF/MF/HF antenna, you should publicly ask which plane was used for the
measurement and when were these measurements made. You can then check
the local airports, if that plain was in the air at that time.

Paul OH3LWR

OH3LWR:

Of course that is what everyone would want to measure, but unless you
are working in the millimeter bands in a non-echoic chamber,
determining the true (absolute) radiation pattern can be quite
problematic.


We are looking at shortened, loaded verticals, monopoles. So you stick the
"standard" - quarter wave radiator in the test point, measure it at proper
point, then you replace it with "miracle" antenna and do the same, feeding them
with the same power. The difference is in overall efficiency. Lets not lose
sight of what are we talking about and what the real "problem" is.
How do you build igloo for 4 square? Comon guys, this is old stuff, has been
done for 100 years already. Lets not fly off on tangents.
Is anyone out there who "calorimetered" the antenna?

Yuri, K3BU

"Yuri Blanarovich" wrote in message
...
So, when you tell me to "forget the igloo", you seem to have placed
yourself in a position where you think you know how to evaluate antenna
efficiency and that I dont. I dont think you are *that* smart.

Jerry


You win, I ain't so smart as I thought. :-)
I thought that antenna is supposed to radiate RF in the direction and with
pattern one desires. That's what I want to measure, how effective radiator
it
is, how much RF it produces at the point of interest.
If you want to know how well it works as a heater, more power to you.
I am not in a ****ing contest who is "smarter", I was trying to convey
some
practicality and what I do and what I am interested in.
Over and out!

Back to DR1 (www.computeradio.us)

Yuri, K3BU

I was under the impression that radiation efficency was pretty much a"
no-brainer".If the antenna is built of quality materials with good
workmanship the antenna would be an efficent radiator with little ohmic or
dielectric losses. The exception to this of course would be antennas that
use an earth ground. I just found I was losing at least 3 db to heating up
the ground.

Jimmie

I was under the impression that radiation efficency was pretty much a"
no-brainer".If the antenna is built of quality materials with good
workmanship the antenna would be an efficent radiator with little ohmic or
dielectric losses. The exception to this of course would be antennas that
use an earth ground. I just found I was losing at least 3 db to heating up
the ground.

Jimmie




Keep digging, you will find more lost dBs. Things get aggravated in loaded
antennas when you start inserting coils, loading elements, folding them back,
etc. Efficiency is roughly proportional to the area under the current
distribution curve along the radiator. That can be affected by any of the
shortening "miraculous" gizmos, like Vincent DLM antenna. It is not just heat
loses in resistances. You can't have "perfectly" conducting piece of 1 ft
copper tubing be as effcient as 130 ft full size radiator on 160m.
Getting smarter, Eh ? :-)

Yuri, K3BU

On Mon, 23 Aug 2004 03:01:53 GMT, "Jimmie"
wrote:

I was under the impression that radiation efficency was pretty much a"
no-brainer".If the antenna is built of quality materials with good
workmanship the antenna would be an efficent radiator with little ohmic or
dielectric losses. The exception to this of course would be antennas that
use an earth ground. I just found I was losing at least 3 db to heating up
the ground.

Hi Jimmie,

3dB heating up the ground with an antenna that has 5dBi gain in the
preferred direction and launch angle compared to an antenna that has
no ground and 0dBi gain in the same preferred direction and launch
angle may give you pause and allow the worms some comfort on a cold
day.

Workmanship and quality materials tests those reputations vastly more
for smaller antennas than standard sized ones. Those 1 meter loops
used for HF are not rated for the lower bands for very good reasons,
and they claim (and I believe them) high standards for their product.
However, if you could resonate them in the 160M band, you'd be lucky
to see 1% efficiency.

Small antennas carry a lot of baggage, and any claims of efficiency
superior to the standard antennas they replace are suspect. When they
qualify that efficiency in creative terms like "more efficient per
unit length" you would do well to skip that and ask for field
strengths out 10 miles. A model called the eh had an FCC style site
survey performed to which they crowed it proved their design was equal
or better to a full size antenna. The data revealed results 10 and 20
miles out were 15-17dB down below that same standard they were so much
more efficient than.

73's
Richard Clark, KB7QHC