"Roy Lewallen" wrote in message
...
"Takeoff angle" can have two meanings. The first, and really a misuse of
the term, is the one used by antenna modeling programs such as EZNEC. It
means the elevation angle at which an antenna's radiation is maximum. This
is a property of the antenna and its local environment (particularly the
height above ground for horizontal antennas, and local ground quality for
vertical antennas).

And I thank very much for the above statement to which I fully agree.
But later you turn away from that statement with respect to the
propagation conditions do you not?


The second meaning is the elevation angle at which propagation occurs.
This is dictated mainly by the propagation path -- the distance and the
effective height of the ionosphere. The antenna pattern can play a role
only when more than one path is possible, for example single and double
hop, by modifying the amount which propagates by each path.he environment

Now Roy I have a problem with what you are saying here
I spend hours modelling an array to lower the TOA or angle of max radiation
which directly controls the main lobe dimension both in width and height.
I model an antenna array such that it emulates in a way a "stacked"
array where as low as a 9/10 degree TOA. The 3 db gain window is broader in
width and narrower
in height than say the normal array. It is this "TOA" that determines what
window we have and
where it hits the ionesphere which thus determines its point of arrival on
the earths surface
Not propagation which is the "environment" of all antenners in the vicinity
and the same
for all antennas at a particular time.
The ARRL clearly shows that it is the TOA that determines the range as it
were of one antenna
comparered to the others with different TOA.. For the life of me I cannot
concurr with the statement
as stated.
I would also add that a antenna with a lower TOA invarably means a thinner
lobe of radiation
as well as a lower 3dB window and in a few cases the underside contour of
the main lobe can
be lower than one of equivalent gain. I use the term TOA as being the line
of maximum gain
In no way do I infer that we have laser type radiation as compared with a
flashlight style radiation


The "takeoff
angle" of the first meaning (angle at which the radiaion is maximum) isn't
a particularly useful measure of and antenna's performance, and it
certainly doesn't determine the real "takeoff angle" of the second meaning
(angle at which propagation occurs).

Then it is here that that we are entangled. I agree the envionment
can affect or deflect radiation, whether it be a mountain face or the
down slope of a mountain, but I do not see how existing propagation
can mold the direction of such radiation, and possibly it is here
that my learning curve can be bettered . To me, propagation affects
first come into being when the ionesphere is able to" turn" or "deflect"
radiation according to the relative angle of impact of that which it turns
and not before. ( when all is said and done this is the crux of the debate)


Art has used "takeoff angle" of the first meaning liberally in his
writings, often with the added and incorrect implication that all the
radiation from an antenna occurs at its "takeoff angle", with none at
other elevation angles. So his confusion about Richard's statement (which
correctly used "takeoff angle" in the second sense) is understandable.

No,
That is not true. My experimentation is aimed at arriving at a low
TOA for an antenna. The reason is two fold

"1" A lower TOA usually means that the upper half of the main lobe is
reduced
and the lower half of the lobe is not reduced. Thus radiation is
contained
within an angle of radiation that is usefull and not wasted as it is with an
antenna of a higher
TOA.

"2" When the attributes of "1" above are achieved it is then possible to
LOWER the underside
of the main lobe contour where one can communicate at lower angles with a
single feed array
and obtain the advantages of multi stacked arrays with multi feed point.

Is this the error of my ways where any change I make to an antennas pattern
is rendered of no use because I must first find a way to manipulate
propagation
where all the action is really at?

I also want to make it clear that I appreciate your post which I see as an
attempt to clarify matters
that are presently being discussed ie.It is propagation and not the antenna
that determines the
TOA. Or "antenna pattern is determined by propagation" so that we don't
get hung up
on the term TOA
Very best regards
Art


Roy Lewallen, W7EL

wrote:
Richard,
You are at it again, avoiding the supply of corroberation to what you
say is true.
Stick to the basic statement that you made, which from their silence, the
gurus concur
with.
Your statement was that:
propagation is what determines TOA
and I ask for confirmation of the correctness of that
statement from you in the nature of some written text.
The gurus obviously accept your statement as fact, but I do not.
Usually you refer to a text to back up your statement ,but this time you
haven't, winging it
and relying solely on the fact that the gurus agree with you.
Surely you or some guru can come up
with a written text that states that propagation is what determine TOA.!
That is what this group is all about where gurus debunk the untruths
and supply the real truths and not to let old wives tale dominate.
You also stated that you made the ":assumption" presumably
based on the "facts" stated above that the Curtain could be considered as
similar to the dipole
since propagation determines that they are the same. This is total junk
,in its entirety,
unless you or the gurus can come up with a written text that confirmes
their positions.
Art