I believe you are correct.
If you understand the question posted over a 100 posts ago why is it
that others are stumbling.
I could not figure out how to determine the volume mathematically so I
took the model making route which confirms the poor efficiency of the
yagi. What blows my mind is the assertion that the major lobe is a
large fraction of the total volume whatever a large fraction really
means ( no hints given by the poster) plus the idea that volume outside
the main lobe is miniscule,.Seems like memorisation of required answers
is the way to go with amateur radio at the moment. Thinking from first
principles obviously not required just give an answer that you want to
give regardless what the question was and then blame the poster because
he didn't pose the correct question for which the answer was well
suited.
If you can't provide an answer then change the subject and then discuss
that
Well I am glad somebody read that first post for what it said not for
what most wanted to read. I feel a lot better now
Art






Dave wrote:
"art" wrote in message
ups.com...
I had to ask rather than assume. My inclination where it came from
which you didn't say was that since the field produced by an actual
antenna is twice as great as the field produced by the isotropic
antenna the gain RATIO is two and the power gain is 2 squared which is
4. this means that to produce the same field strength at the same
distance, four times as much power would have to be supplied to an
isotropic radiator as to the actual antenna under consideration. But as
I stated many times RATIO as you are using it has not interest to me as
it is not relevant.
What you are doing is based on a RATIO at a given plane and that RATIO
changes with the plane examined. That is why the yagi is termed a
planar array In other words a reflector is used to affect a single
plane of radiation it is not all encompassing of the total rear
radiation. On top of all that the plane chosen is along the plane of
the main lobe only and does not in anyway include the ratio of the
second lobe to the rear or any nulls that are made. The rear radiation
fields is no way a mirror image of the forward radiated field. You are
supplying a conventional answer to a convential question which revolves
around a single plane where I am speaking of the total radiation field.
You can't keep trotting out the conventional answer to the question
that you want to be posed. I am sure glad I didn't guess where you were
getting the figure 4 from otherwise the thread would have been 200
posts long plus a lot of accusations as to who said what.Get back to
basics and stop trying to section the field of a dipole to make it
easier to simplify for newcomers, it does not represent factually
everything.
it is just a means to an end. without involvement in the toital "wave
and fields" subject
As I have oft times stated I am looking at the whole pattern in three
dimensional form and you keep trotting out answers based on a two
dimensional format
Art


then i would suggest learning some of the nitty gritty details of a program
like nec and figure out how to integrate it's field values over the 3d
surface and sort out the values you are interested in. no one here will do
that for you since it is normally not of interest in amateur antenna design.
we all understand how to evaluate the performance of antennas for our
'normal' uses in terms of gain and f/b ratio and how to read those 2d slices
to evaluate side lobes for our 'normal' uses. as you have stated it your
desire is not a normal one, you have special requirements which will require
a special solution that is not readily available for amateur antennas....
maybe that data is available for large satellite or deep space dishes where
they worry about extreme details of side lobe power and noise temperatures,
but not for hf ham use with normal antennas.

art wrote:
I believe you are correct.
If you understand the question posted over a 100 posts ago why is it
that others are stumbling.
I could not figure out how to determine the volume mathematically so I
took the model making route which confirms the poor efficiency of the
yagi. What blows my mind is the assertion that the major lobe is a
large fraction of the total volume whatever a large fraction really
means ( no hints given by the poster) plus the idea that volume outside
the main lobe is miniscule,.Seems like memorisation of required answers
is the way to go with amateur radio at the moment. Thinking from first
principles obviously not required just give an answer that you want to
give regardless what the question was and then blame the poster because
he didn't pose the correct question for which the answer was well
suited.
If you can't provide an answer then change the subject and then discuss
that
Well I am glad somebody read that first post for what it said not for
what most wanted to read. I feel a lot better now
Art






Dave wrote:
"art" wrote in message
ups.com...
I had to ask rather than assume. My inclination where it came from
which you didn't say was that since the field produced by an actual
antenna is twice as great as the field produced by the isotropic
antenna the gain RATIO is two and the power gain is 2 squared which is
4. this means that to produce the same field strength at the same
distance, four times as much power would have to be supplied to an
isotropic radiator as to the actual antenna under consideration. But as
I stated many times RATIO as you are using it has not interest to me as
it is not relevant.
What you are doing is based on a RATIO at a given plane and that RATIO
changes with the plane examined. That is why the yagi is termed a
planar array In other words a reflector is used to affect a single
plane of radiation it is not all encompassing of the total rear
radiation. On top of all that the plane chosen is along the plane of
the main lobe only and does not in anyway include the ratio of the
second lobe to the rear or any nulls that are made. The rear radiation
fields is no way a mirror image of the forward radiated field. You are
supplying a conventional answer to a convential question which revolves
around a single plane where I am speaking of the total radiation field.
You can't keep trotting out the conventional answer to the question
that you want to be posed. I am sure glad I didn't guess where you were
getting the figure 4 from otherwise the thread would have been 200
posts long plus a lot of accusations as to who said what.Get back to
basics and stop trying to section the field of a dipole to make it
easier to simplify for newcomers, it does not represent factually
everything.
it is just a means to an end. without involvement in the toital "wave
and fields" subject
As I have oft times stated I am looking at the whole pattern in three
dimensional form and you keep trotting out answers based on a two
dimensional format
Art


then i would suggest learning some of the nitty gritty details of a program
like nec and figure out how to integrate it's field values over the 3d
surface and sort out the values you are interested in. no one here will do
that for you since it is normally not of interest in amateur antenna design.
we all understand how to evaluate the performance of antennas for our
'normal' uses in terms of gain and f/b ratio and how to read those 2d slices
to evaluate side lobes for our 'normal' uses. as you have stated it your
desire is not a normal one, you have special requirements which will require
a special solution that is not readily available for amateur antennas....
maybe that data is available for large satellite or deep space dishes where
they worry about extreme details of side lobe power and noise temperatures,
but not for hf ham use with normal antennas.

The major lobe is a very large portion of the total power, it has been
figured out but I doubt if anyone wants to figure it out again for any
particular yagi. I know I could care less, but it is obvious from
looking at the plotted radiation patterns that sidelobe power is very
small amount easily in the 2% ball park of the total amount. Of course
some yagis will be better at concentratining the power in the main
lobe than others. By the way ther is 3d yagi antenna pattern
information available. Just find plots for the antenna mounted
horizontally and vertically. This is something almost any antenna
simulation program can provide.

JIMMIE wrote:
art wrote:
I believe you are correct.
If you understand the question posted over a 100 posts ago why is it
that others are stumbling.
I could not figure out how to determine the volume mathematically so I
took the model making route which confirms the poor efficiency of the
yagi. What blows my mind is the assertion that the major lobe is a
large fraction of the total volume whatever a large fraction really
means ( no hints given by the poster) plus the idea that volume outside
the main lobe is miniscule,.Seems like memorisation of required answers
is the way to go with amateur radio at the moment. Thinking from first
principles obviously not required just give an answer that you want to
give regardless what the question was and then blame the poster because
he didn't pose the correct question for which the answer was well
suited.
If you can't provide an answer then change the subject and then discuss
that
Well I am glad somebody read that first post for what it said not for
what most wanted to read. I feel a lot better now
Art






Dave wrote:
"art" wrote in message
ups.com...
I had to ask rather than assume. My inclination where it came from
which you didn't say was that since the field produced by an actual
antenna is twice as great as the field produced by the isotropic
antenna the gain RATIO is two and the power gain is 2 squared which is
4. this means that to produce the same field strength at the same
distance, four times as much power would have to be supplied to an
isotropic radiator as to the actual antenna under consideration. But as
I stated many times RATIO as you are using it has not interest to me as
it is not relevant.
What you are doing is based on a RATIO at a given plane and that RATIO
changes with the plane examined. That is why the yagi is termed a
planar array In other words a reflector is used to affect a single
plane of radiation it is not all encompassing of the total rear
radiation. On top of all that the plane chosen is along the plane of
the main lobe only and does not in anyway include the ratio of the
second lobe to the rear or any nulls that are made. The rear radiation
fields is no way a mirror image of the forward radiated field. You are
supplying a conventional answer to a convential question which revolves
around a single plane where I am speaking of the total radiation field.
You can't keep trotting out the conventional answer to the question
that you want to be posed. I am sure glad I didn't guess where you were
getting the figure 4 from otherwise the thread would have been 200
posts long plus a lot of accusations as to who said what.Get back to
basics and stop trying to section the field of a dipole to make it
easier to simplify for newcomers, it does not represent factually
everything.
it is just a means to an end. without involvement in the toital "wave
and fields" subject
As I have oft times stated I am looking at the whole pattern in three
dimensional form and you keep trotting out answers based on a two
dimensional format
Art


then i would suggest learning some of the nitty gritty details of a program
like nec and figure out how to integrate it's field values over the 3d
surface and sort out the values you are interested in. no one here will do
that for you since it is normally not of interest in amateur antenna design.
we all understand how to evaluate the performance of antennas for our
'normal' uses in terms of gain and f/b ratio and how to read those 2d slices
to evaluate side lobes for our 'normal' uses. as you have stated it your
desire is not a normal one, you have special requirements which will require
a special solution that is not readily available for amateur antennas....
maybe that data is available for large satellite or deep space dishes where
they worry about extreme details of side lobe power and noise temperatures,
but not for hf ham use with normal antennas.

The major lobe is a very large portion of the total power, it has been
figured out but I doubt if anyone wants to figure it out again for any
particular yagi. I know I could care less, but it is obvious from
looking at the plotted radiation patterns that sidelobe power is very
small amount easily in the 2% ball park of the total amount. Of course
some yagis will be better at concentratining the power in the main
lobe than others. By the way ther is 3d yagi antenna pattern
information available. Just find plots for the antenna mounted
horizontally and vertically. This is something almost any antenna
simulation program can provide.


Like other I didnt understand the equestion as origionally posted
either. This was probably due to your false statement requardinding the
efficency or lack there of as you define efficentcy
of a yagi antenna. AS you say that you can take a look at an antenna
plot see that it is obviously inefficent without showing the mathmatics
I can look at one and tell you it is very efficent per your own
definition without giving the numbers. I can only assume you are
confused by the fact the plots are drawn with a LOG scale as opposed to
a linear scale. If drawn using a linear scale the side lobes would be
1/100 to 1/1000 the size of the main beam. If you dont want to take my
word for simply take any yagi antenna plot and redraw it to a linear
scale.

art wrote:

Cecil, efficiency depends on what your objectives are
snip bull****
Art.

Art

You are obviously much smarter than every one here combined. So I will
leave it up to you to design the antenna(s) that no one has been able to
come up with before this miracle antenna you envision. The tens of
millions of man hours we have put into antenna developement cannot
possibly equal your intelligence.

Prove everyone wrong. Go ahead. We're waiting.

tom
K0TAR

Richard Clark wrote:

On 29 Sep 2006 05:47:14 -0700, "art" wrote:


one having only a 6 dB front/back ratio.


But that 4:1 figure where does it come from?


Hi Art,

Do you know how to work a calculator using logarithms?

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On 29 Sep 2006 05:47:14 -0700, "art" wrote:


one having only a 6 dB front/back ratio.


But that 4:1 figure where does it come from?


Hi Art,

Do you know how to work a calculator using logarithms?

73's
Richard Clark, KB7QHC

Which reminds me, I wanted to start a thread on calculators.

tom
K0TAR

Tom Ring wrote:

SNIPPED


Which reminds me, I wanted to start a thread on calculators.

tom
K0TAR

Calculator: definition - One person with one brain, one pencil, one piece of
paper, and knowledge of math [Oh my gosh! I'll have to spend time learning
something. Does that mean I'll have to study to get a license?]

art wrote:
Dan,
you know quite well what the post that started this thread asked for.
I only added the TOA comments to fill in some body where I was
coming from not for advice on what antenna to build.
People are quibling over the word "efficiency" which I find rather
wierd
especially since I am supposed to be in the company of fellow
engineers.

Interesting Art, you find that weird, and I find it as an explanation! 8^)

- 73 de Mike KB3EIA -