Richard Clark wrote:

Hi All,

The method described by the paper offered above is a commonplace of
Metrology called "Reciprocity." I have calibrated precision
microphones against this method, and the error math offered is
consistent with my experience (much less the actual values offered as
examples).


Any references on microphone calibration? Maybe a short tutorial? That
is something I have a need to do.

tom
K0TAR

"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.

O.K. Roy let's get down to the nitty gritty and look at this question.
Your background in antenna programs makes you a person of choice
to declare if what I do is a waste of time and where I must default to an
experts judgement.
A month or so ago I gave a description of the antenna that I modelled
and for your interest I used the AOP program by Beasely a person
that you have collaborated with in the past.
One can design a yagi antenna with 8 elements say on a 60 foot boom
and then note the gain and the elevation angle of maximum gain.
This can be done using the most basic antenna program available.

The next step is to apply this same antenna to a program that is capable
of changing dimensions to obtain a desired function ,which in this case can
be
"Gain". There is reference to a NEC program on this group during the past
week
or so that I believe is capable of doing this, that is on the web and also
free to all.
With the use of variable dimensions which includes best x,y and Z positions
for various pulses or physical positions the program will procede to do as
asked.

This test is about as simple as it gets to show how the angle of max
radiation can be changed
as well as the envelope of the new angle range to achieve a 3 dB window of
radiation

You will see that the computor program will immediately remove itself
from a Yagi design to obtain a better gain and form an array that consists
of one driven element and where the rest are all reflectors!
Though the final shape appears to represent a dish it is not, it is simply a
design with multiple dimentional reflectors in the best coupling mode.
The result is a gain figure that will exceed the original design,
which is what we requested of the program i.e.allow it to make changes of
choice
to achieve a higher gain than the initial yagi design
With the above. one can change the elevation angle for maximum gain which
has now
dropped to a 11 to 10 degrees or even 9 degrees if one is willing to
sacrifice some gain.
This can be also be achieved by allowing the driven element to deviate from
a straight dipole
to a vee shape tipped in such away to helps control reactance swings of the
total array.
The above is quite simple to duplicate, where anybody can place a 8 element
yagi with a long boom
of 60 ft placed over real ground and challenge the program to devise a way
of increasing gain.
In my case the program changes to a non director mode without any prodding,
other programs
may well need some prodding. Changes to elevation for maximum gain will
change automatically
and one can expect to easily devise an array with a 10 degree angle where a
gain of 16 dbi is attained
as well as a broader lobe than can not be accomplished with a Yagi design.
If you find that you cannot repeat the above results in a short space of
time then it surely reflects
a misuse of programs on my part.
Please note that propagation has no part in forming the shape of the main
lobe to the
best of my understanding but you would know better than most as to what the
program parameters actually are
I look forward to your response or any other program users response that
shows my findings
are a waste of time so I can direct my experimentation in a more fruitfull
direction.
Best regards
Art




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
snip


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
snip
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.
Snip


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

snip

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.


Best regards
Art
Roy Lewallen, W7EL

wrote:
"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?

Because "takeoff angle" as you use the term does not bear a direct
relationship to the ability to communicate.

Roy Lewallen, W7EL

Roy Lewallen wrote:

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.
snip
Roy Lewallen, W7EL

Roy

The Canadian with 2 calls, VE3GK/VE2GK, Gerry King, made a very nice 20
meter antenna system, which he gave a great talk about at our local
hamfest in northern NY back around 1978 +-. This system was unique, at
least then, in that he had 2 20 meter beams that could be used singly,
upper or lower, or as a stack, and could independently vary their
heights. He reported very good success, since he could vary the angle
of greatest radiation at will.

He is now a silent key, unfortunately, but his site is still up. I will
leave it to those interested to find it, it's not hard, but his heirs
don't need useless traffic. I am not sure if his old system is pictured
on the page.

tom
K0TAR

Reg, G4FGQ wrote:
"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."

Confuse the readers?

Geometry and trigonometry are involved. What`s more, the signal may take
more than one path between only two points, or multiple hops, or
multiple azimuths. This causes fading and distortion.

Transmitted energy in directions other than to a receiver is wasted.
That`s one of several reasons to use antenna directivity in azimuth and
elevation.

Maybe Cecil`s IEEE Dictionary defines TOA. The references I`ve found are
to "elevation angle" above the horizon.

In general, an antenna`s angle of maximum response is lowered by raising
the antenna height. If you have stacked horizontal elements you can
adjust their phasing to skew the elevation angle up or down some.

An ideal HF antenna may be a giant array of dishes that might be aimed
for one-hop, if possible, in a multiple diversity system.

Something almost as good is a triple diversity system which uses
rhombics. 3 receiving rhombics are plavced with about 10-wavelengths of
lateral spacing at the lowest frequency received. Multicouplers on each
rhombic feed various receivers , often at various frequencies. Diversity
combiners select the best received signal of three carrying the same
program. The results are spectacular. We used such TDR systems for
broadcast program relay. Often the quality was as if the program arrived
by cable.

Best regards, Richard Harrison, KB5WZI

Richard Clark says -
Hi Reg,
I thought Wes' link was quite specific to the matter:
=====================================

Hi Richard,
I originally wrote -

"Does anyone have typical examples of measurement uncertainties
claimed
by antenna testing stations? Answers in decibels please."

The two links to papers, kindly found by Wes, are both devoted to
microwave horns and dishes. Very interesting and directly related to
the subject.

But in anticipation of the sort of replies I would receive, and in
fact did receive, I specifically asked -

"A reply from a testing station, at HF or VHF, would be specially
appreciated."

It appears that at microwaves a worst-case uncertainty of 0.2 dB, that
is a range of nearly half dB, is achievable in the National Physical
Laboratory at Teddington on Thames, London. Which is a little hard for
an Old Timer like me to believe. But at HF and VHF, at which amateurs
are mostly interested, the uncertainty on a typical open-air range is
sure to be greater. If only because great accuracy of rocket
technology at the lower frequencies is not needed.

It nearly always occurs that technical enquries at LF and HF get lost
in the elevated mysteries of microwaves, circulators and
scattering-parameters.

I am unfamiliar with precision antenna test and measurement methods. I
don't particularly wish to know. But if you, as an employee of a
reputable laboratory, were given the job of determining the forward
and reverse gains of fractal or other weird antennas, at 7 MHz and
144 MHz, what uncertainties would you state? I'd believe you.
----
Reg, G4FGQ.

On Tue, 26 Apr 2005 19:15:44 -0700, Roy Lewallen
wrote:

wrote:
"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?

Because "takeoff angle" as you use the term does not bear a direct
relationship to the ability to communicate.

Right on.

Let's look at it this way. If I have an antenna with a "pencil beam"
and it's pointing at 90 degree azimuth and the station I want to
communicate with is at 0 degrees, I don't know of anyone who would say
that this is an optimum situation.

Yet, many (okay, one) would say that an antenna with (pardon me) a
"take off angle" of 3 degrees is *always* superior to one with a TOA
of 20 degrees, notwithstanding the fact that the desired station's
signal is maximum at 20 degrees.

This is like saying that I have room for a rhombic pointed at Asia so
I'm going to work my ass off optimizing it when all of the stations I
want to work are in Europe.

Why is this so? I'm completely baffled.

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

Because "takeoff angle" as you use the term does not bear a direct
relationship to the ability to communicate.

O.K. Roy if you are going to let this discussion revolve solely around the
term
of TOA which is a datum line around which the main lobe evolves,, A term you
have voiced
opposition to over the years and which you personally use in your own
antenna program design
then you will be succesfull in any debate regarding antennas. I have stated
many times that the
elevation angle denotes the line of maximum gain and the lobe that surrounds
this angle denotes
the area of communication ability represented by the oft used term of the 3
dB window.
You are refusing to accept the use of this term because of personal
emotional reasons,
that you only use the term under protest because of commercial reasons and
now as a basis for rejecting.
new knoweledge supplied by computor programs.,. presumably by clinging to
"all is known" mantra
I will never persuade you to view this thread with an open mind.
You have stated that TOA as I describe the term does not bear a direct
"relationship "
to the ability to communicate which obviously must relate to a part of a
post where you
envision that you have accomplished a "gottcha".
One person stated that everybody knows that I am right which I question,
especially
since you have now come forward with contrary thoughts.
Roy, there can be no debate if one must always accept
all your statements in Pope like fashion that excludes discussion.
Best regards
Art
Roy Lewallen, W7EL

Richard Harrison wrote:
Maybe Cecil`s IEEE Dictionary defines TOA. The references I`ve found are
to "elevation angle" above the horizon.

Nope, none of my references mentions TOA.
--
73, Cecil http://www.qsl.net/w5dxp


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I believe "takeoff angle" is in the same category as "capture area" and
"S-unit" -- terms which nobody except amateurs seem to need.

Roy Lewallen, W7EL

Cecil Moore wrote:
Richard Harrison wrote:

Maybe Cecil`s IEEE Dictionary defines TOA. The references I`ve found are
to "elevation angle" above the horizon.


Nope, none of my references mentions TOA.
--
73, Cecil http://www.qsl.net/w5dxp