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.