"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

On Tue, 26 Apr 2005 08:16:56 +0100, Ian White GM3SEK
wrote:



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3s


So you've finally emigrated Ian!

Good luck in the move..

Peter, G3PHO

O.K. Richard I'll leave it at that with you . You continue to send
prewritten responses to questions that were not asked.or do not pertain to
the subject at hand
I will leave it to you to alert all antenna labs not to test antennas when
there is no
propagation or, failing that, leave a bucket under the antenna to compensate
for the lack of TOA
or elevation angle because of the lack of propagation generated modifying
actions..
I don't know that if they leave the door open during testing it will
suffice.
You can always supply a written technical text to justify youir actions when
you find it.
Nuf said
Art


"Richard Harrison" wrote in message
...
Art Unwin wrote:
"Surely you or some guru can come up with written text that states that
propagation is what determines TOA."

I don`t find TOA in any index. I find "elevation angle", which I suppose
is a synonym, in my 19th edition of The ARRL Antenna Book. On page 2-9
it says:
"The elevation angle is referenced to the horizon at the earth`s surface
, where the elevation angle is 0-degrees."

On page 3-5, the same book says:
"Now look at Fig. 4A, which compares the computed vertical-angle
response for two half-wave dipoles at 14 MHz."

The Antenna Book is not very definitive.

"Transmission Lines, Antennas, and Wave Guides" on page 314 says:
In order to escape from the earth without excessive ground attenuation,
a sky wave must leave the earth at an angle of at least 3-degrees above
the horizon.---At 3-degrees elevation, the distance per hop is about
3,500 km (2,100 miles). Longer distances are automatically broken up
into units not exceeding 3.500 knm."

It`s the medium breaking up the hops, not the antenna.

Best regards, Richard Harrison, KB5WZI

wrote:
. . .
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.

And, as I've said quite a few times in one way or another, it's largely
a waste of time.

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

That's absolutely incorrect. All antennas radiate at all angles. The
ionosphere doesn't know or care at what angle your antenna is radiating
the most -- propagation will occur at the angle favored by the
ionosphere at the time. Your antenna's pattern doesn't dictate the
geometry of the path.

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.

By speaking of "environment" I was not including propagation, and in
conforming to traditional usage, I also don't include propagation when
speaking of antenna patterns. An antenna pattern is a polar plot of the
field intensity of the antenna at a distant point, but with the
assumption that the propagation to all points is lossless. The actual
signal received at a distant point requires the inclusion of propagation
effects. The pattern is one element in the equation, but only one.

. . .


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?
. . .

Close. Sometimes two or more propagation modes are possible, such as
single and double hop. From here to say, New York, I might have single
hop at 3 degrees and double hop at 12. (Please forgive me if those
particular propagation angles can't really occur at the same time, but
they're in the ballpark.) It doesn't matter one iota what the angle of
maximum radiation from my antenna is. All that matters is the gain or
field strength at elevation angles of 3 and 12 degrees. All the rest of
the radiation will go some place besides New York. As a general rule, I
can get a stronger signal to New York with X dBi at 3 degrees than the
same gain at 12, because the single hop path loss is usually less. So it
might pay me to maximize my gain at that angle at the expense of 12
degrees. On the other hand, the other station's antenna pattern is just
as important -- if it has a lot more gain at 12 degrees than 3, he might
not hear me if I put out most of my energy at 3 rather than 12. But in
any case, it doesn't matter how much I'm radiating at 1, 5, 7, or 15
degrees, or what my antenna's maximum angle is. All that counts is how
much I'm radiating at 3 or 12 degrees. Other than manipulating your
antenna to radiate more or less at those two angles, you don't get to
"manipulate propagation" to support other angles at a given time,
frequency, and path. You're stuck with those until the ionosphere
changes. Knowledgeable DXers (which I'm not) spend a lot of time working
out what the angles will be for propagation to various target locations,
and how to design, build, and switch antennas to maximize the amount of
radiation at those angles.


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

No, antenna pattern isn't determined by propagation. The signal strength
at the other end of the path is determined by the gains of both the
transmit and receive antennas at the elevation angle of propagation, and
the loss along the path. Period. Notice that "takeoff angle" and
"pattern" didn't appear in that sentence. And you don't get to choose
the angle of propagation (unless more than one are supported at a given
time, which is only sometimes true, and then you can only choose between
the supported angles).

I suggest downloading the excellent, free, and easy to use propagation
software by Shel Shallon, W6EL, http://www.qsl.net/w6elprop/. In a few
minutes, you'll be able to see what angles are supported at a given time
and frequency for a given path.

Roy Lewallen, W7EL

On Tue, 26 Apr 2005 19:59:59 +0000 (UTC), "Reg Edwards"
wrote:

But for the two figures to be of value the uncertainties in the
determination should be stated on the certificate (a legal document).

What are TYPICAL uncertainties, in dB, which appear above the Head of
the Laboratory's signature.

Hi Reg,

I thought Wes' link was quite specific to the matter:
Measurement Mismatch Correction Error 0.04
Noise Power of Power Sensor 0.00
Zero error of Power Sensor 0.00
Power Meter Linearity 0.04
Space Loss Measurement Error 0.01
Multipath Curve Fitting Random Error 0.04
Proximity Effect Correction Error 0.05
All expressed in dB and may be combined using the usual methods of
RMS, RSS, or worst case simple sum.

73's
Richard Clark, KB7QHC

Peter wrote:

So you've finally emigrated Ian!

Still commuting, but G3SEK is definitely QRT so I changed the signature.
I'm hoping to get on the air from GM next week.

Web URLs will still be "g3sek" but e-mail to either
will be OK.


Good luck in the move..

Thanks, I'll keep those good wishes in my back pocket!


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Roy Lewallen" wrote in message
...
wrote:
. . .
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.

And, as I've said quite a few times in one way or another, it's largely a
waste of time.

Why? A single word question
On what authority do you base that statement on?



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

That's absolutely incorrect. All antennas radiate at all angles. The
ionosphere doesn't know or care at what angle your antenna is radiating
the most -- propagation will occur at the angle favored by the ionosphere
at the time. Your antenna's pattern doesn't dictate the geometry of the
path.

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.

By speaking of "environment" I was not including propagation, and in
conforming to traditional usage, I also don't include propagation when
speaking of antenna patterns. An antenna pattern is a polar plot of the
field intensity of the antenna at a distant point, but with the assumption
that the propagation to all points is lossless. The actual signal received
at a distant point requires the inclusion of propagation effects. The
pattern is one element in the equation, but only one.

. . .


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?
. . .

Close. Sometimes two or more propagation modes are possible, such as
single and double hop. From here to say, New York, I might have single hop
at 3 degrees and double hop at 12. (Please forgive me if those particular
propagation angles can't really occur at the same time, but they're in the
ballpark.) It doesn't matter one iota what the angle of maximum radiation
from my antenna is. All that matters is the gain or field strength at
elevation angles of 3 and 12 degrees. All the rest of the radiation will
go some place besides New York. As a general rule, I can get a stronger
signal to New York with X dBi at 3 degrees than the same gain at 12,
because the single hop path loss is usually less. So it might pay me to
maximize my gain at that angle at the expense of 12 degrees. On the other
hand, the other station's antenna pattern is just as important -- if it
has a lot more gain at 12 degrees than 3, he might not hear me if I put
out most of my energy at 3 rather than 12. But in any case, it doesn't
matter how much I'm radiating at 1, 5, 7, or 15 degrees, or what my
antenna's maximum angle is. All that counts is how much I'm radiating at 3
or 12 degrees. Other than manipulating your antenna to radiate more or
less at those two angles, you don't get to "manipulate propagation" to
support other angles at a given time, frequency, and path. You're stuck
with those until the ionosphere changes. Knowledgeable DXers (which I'm
not) spend a lot of time working out what the angles will be for
propagation to various target locations, and how to design, build, and
switch antennas to maximize the amount of radiation at those angles.


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

No, antenna pattern isn't determined by propagation.

Whoopee

The signal strength
at the other end of the path is determined by the gains of both the
transmit and receive antennas at the elevation angle of propagation, and
the loss along the path. Period. Notice that "takeoff angle" and "pattern"
didn't appear in that sentence. And you don't get to choose the angle of
propagation (unless more than one are supported at a given time, which is
only sometimes true, and then you can only choose between the supported
angles).

It is up to the user to design the antenna with the pattern of choice
and that is what I did. And you can do it to since you are familiar
with antenna programs. You just have to point the initial program so it
is able to spot what dimensions are required to produce the required
pattern.
Roy please go back to the top and answer that simple one word question
and let it all hang out
Best regards
Art


I suggest downloading the excellent, free, and easy to use propagation
software by Shel Shallon, W6EL, http://www.qsl.net/w6elprop/. In a few
minutes, you'll be able to see what angles are supported at a given time
and frequency for a given path.

Roy Lewallen, W7EL

Richard, why don't you just say that the angle of elevation of the
radio path has nothing whatsoever to do with the type of transmitting
and receiving antennas, or the directions in which they may be
pointing or elevated, or even the operating frequency.

When communication has been established between A and B, the angle of
elevation depends only on the locations of A and B on the Earth's
surface, on the number of hops, on the height of the ionospheric
layers, and on the slope of the layers.

The elevation angle is determined purely by trigonometry.

It tends to be the same at both A and B. There may be simultaneously
more than one path and therefore more than one angle. In which case
multi-path distortion and fading occurs.

Received signal strength depends on the two antenna gains in the
direction of the path. The take-off angle predicted by Eznec-type
programs is an altogether different thing. It depends on reflections
from the ground in the vicinity of the two antennas. It does however
have an effect on received signal strength but is of use only when the
locations of A and B and all other geographic and ionospheric
variables are known. They seldom are! As are ground conditions.
----
Reg, G4FGQ.

Richard, I can agree with that
Wes obviously paid close attention to Reggies initial post
and replied in a way that was very informativeI and reflected
his knoweledge in that particular field
Nobody else came even close
to identifying Reggies needs and responded
in such a professional manner.

He should be congratulated
Regards
Art


"Richard Clark" wrote in message
...
On Tue, 26 Apr 2005 19:59:59 +0000 (UTC), "Reg Edwards"
wrote:

But for the two figures to be of value the uncertainties in the
determination should be stated on the certificate (a legal document).

What are TYPICAL uncertainties, in dB, which appear above the Head of
the Laboratory's signature.

Hi Reg,

I thought Wes' link was quite specific to the matter:
Measurement Mismatch Correction Error 0.04
Noise Power of Power Sensor 0.00
Zero error of Power Sensor 0.00
Power Meter Linearity 0.04
Space Loss Measurement Error 0.01
Multipath Curve Fitting Random Error 0.04
Proximity Effect Correction Error 0.05
All expressed in dB and may be combined using the usual methods of
RMS, RSS, or worst case simple sum.

73's
Richard Clark, KB7QHC

Art, propagation does indeed determine the takeoff angle. Let's call that
pTOA. An antenna also has a design takeoff angle. We will call that aTOA.

I think you may be using the term applied to an antenna, Don't confuse it
with pTOA. two different animals with the same name.

" wrote in message
news:zgube.16975$c24.6191@attbi_s72...
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


"Richard Harrison" wrote in message
...
Art Unwin wrote:
"---may I go back to the "compared to a dipole" statement which Richard
keeps brushing off."

I accept a resonant dipole reference as a given.

It is true that the antenna under test and the reference dipole have
different radiation patterns. Our goal was to compare received signal
strengths at locations of interest.

The assumption was that on average, the propaqgation was nearly the same
for the signals received from both transmitting antennas. Good or bad
propagation, the difference between the signals depended on gain in the
direction of the receiver as the transmitted power was the same to both
antennas no matter where it landed.

Kraus says on page 535 of his 3rd edition of "antennas":
"Suppose that we express the gain with respect to a single lambda/2
element as the reference antenna. Let the same power P be supplied to
this antenna. Then assuming no heat losses, the current Io is the sq rt
of the power divided by the resistance of the reference antenna.

In general, the gain in field intensity of an array over a reference
antenna is given by the ratio of the field intensity from the array to
the field intensity from the reference antenna when both are supplied
with the same power P."

Kraus` example was our intended case.

Our expectations were met and our contractors were paid.

Best regards, Richard Harrison, KB5WZI