wrote:
. . .
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.

. . .

Roy, there can be no debate if one must always accept
all your statements in Pope like fashion that excludes discussion.
Best regards

This sort of response doesn't constitute a debate, and it's nothing I
see any need or desire to respond to.

Roy Lewallen, W7EL

No that is not what it is all about. Some here object to the term of TOA and
want strict adherence to the description in terms of "elevation angle".
This same subject came up a few months ago and went on for a long time.
Now we are at it again and allowing the discussion to supplant original
thoughts.
You can now see that somebody has inventing a statement
in straw man fashion and then using the lie as a truthful fact
for the basis of an illicit attack.
Anything goes
I'll wager if you look up the thread of a few months ago
on a TOA thread you will see contrary postings by the same persons
that are posting now, this purely for the sake of a continueing augument.
This group will never agree to anything other than all is known about
antennas
and will fight to the death if anybody alludes to anything that conflicts
with this.
It is for that reason the debate has been throttled and why TOA as shown in
some
computor programs is used as a diversionary tactic.

I give up !

The world is flat.
I will not disagree with that statement anymore
so that emotions can now settle down and I can live in peace

In addition:
All is really known about antennas since there is no evidence
of a scientific book that has been written about what is unknown
about antennas.

In addition :
I urge all newcomers to the hobby to accept the notion
that propagation can modify radiation immediately after emmission
from a radiating antenna , this being a consensus of viewa by noted
Gurus in the hobby

In addition
If a commercial computor program uses the term of TOA
then it is not to be trusted aince it is based around terms
that are known to be invalid and it must be left to the user
to determine how far this invalidity extends with respect
to results obtained. Many commercial programs use this
same term so it is a case of buyer beware.

Best regards
Art




"Fred W4JLE" wrote in message
...
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

On Tue, 26 Apr 2005 21:09:07 -0700, Roy Lewallen
wrote:

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

Hmmm,

Capture area of antennas, 899, 927 of Terman's "Electronic and Radio
Engineering. The 899 reference appeals to aperture. The 927
reference gives a value of 1.5 or 0.12 lambda² (also called intercept
area or antenna cross section) for a common dipole.

Using the co-equivalent aperture, from "Fields and Waves...," Ramo et
al., 581, 607-623. The 581 reference is to using reflectors and
lenses. The section length treatment relates to literal openings
masking a source of radiation.

Capture area, 255, 298-301, 495-496 from "TV and Other Receiving
Antennas," Bailey - which basically reduces a standard half wave
antenna's area to being one half wave long by one quarter wave in
width. When we look at the math offered in a later chapter (pg 299)
it reduces to 0.12 lambda² a figure already described by Terman. "As
we said before, the use of discrete boundaries is a matter of
practical convenience." However, Bailey offers a treat in presenting
the "capture area" of Arrays of various sizes:
# elements Area (lambda²)
1 .125
2 .25
4 0.5
and so on (naively presuming a 3 dB gain with each doubling of
elements).

As these first three draws off the library shelf have companions on
the same shelf with similar coverage, further examples would be
redundant.

The terms of S-Unit and Take-off angle are more an issue of
researching commercial and retail sources than academia. There is
some element of elitism in this; but having found that there are
volumes of instruction to be found in the commercial world that are
barely revealed in the ivory towers, I am not necessarily impressed
with sterile pedigrees (the IEEE dictionary is a monument of
impotence).

73's
Richard Clark, KB7QHC

On Wed, 27 Apr 2005 03:01:20 +0000 (UTC), "Reg Edwards"
wrote:

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.

Hi Reggie,

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
The errors remain across all applications, only the assigned values
change. If I arbitrarily scaled all values by 25, few could challenge
the numbers.

At 7MHz we can all agree that the errors are going to be inversely
proportional to the astronomical cost to determine. No one is going
to perform it at HF when they can only afford 1/100th scale models
that offer the accuracies implied above. What would spending more
money buy them anyway?

73's
Richard Clark, KB7QHC

On Wed, 27 Apr 2005 03:11:34 GMT, "
wrote:

a basis for rejecting.
new knoweledge supplied by computor programs

Hi Art,

More baloney cut thick. You have NOWHERE offered any discussion of
ANY new knoweledge (sic); but you hug such manufactured sentiments
like an emotional life preserver.

You rctleeny challngeed Roy for his athortuy. You wloud do well to
leran spllenig bfoere ripeteang that aigan.

73's
Richard Clark, KB7QHC

Reg Edwards 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.

Or even the existence of the human race and their radio transmitters.
The propagation paths are still there, and even if we had never invented
radio they would still exist.

Antenna engineering is all about making the best use of the propagation
paths that Nature provides[*].

That basic fact should be "bleedin' obvious".

[*] The HAARP project does aim to change the ionosphere itself - but the
colossal size and power of HAARP only goes to show that "the rest of us"
can NOT do that. We cannot change propagation; we can only use it.

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.

A handy phrase that hasn't been mentioned yet is "ray tracing". That is
what we're doing, same as in optics.


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.

Hmm... at the risk of proliferating TLAs, how about making a fresh start
and calling that the antenna's BVA - Best Vertical Angle?

BVA belongs to the antenna, and TOA belongs to the propagation path.

It doesn't get around the fact that the antenna radiates something at
*all* vertical angles, but it's better than the present situation of
(mis)using TOA for two different things.


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

On Tue, 26 Apr 2005 20:28:01 -0500, Tom Ring
wrote:
Any references on microphone calibration? Maybe a short tutorial? That
is something I have a need to do.

Hi Tom,

Standard microphones (I am being quite specific in terminology here)?

I googled with the terms
B&K microphone reciprocity
and the first hit looks as good as any:
http://www.bksv.com/pdf/Bv0051.pdf
As a treat, it offers a discussion of matching with transmission line
metaphors.

I should point out that reciprocity means exactly that! The
microphone should be capable as acting as a loudspeaker (certainly not
too loud) when driven. Standard microphones are capable of accuracies
in the 1/100ths of a dB (and this is an extremely conservative
statement). If you are playing with retail microphones, and follow
the math, you should be able to cobble up something to the nearest
1/4th dB.

If your application conforms to this discussion, you may visit the
Brüel & Kjær website to find deeper references. They are the
pre-eminent makers of precision sound equipment. As I pointed out in
another posting relating to the poverty of academia on many technical
subjects, the commercial field often leads the way in actual
instruction.

73's
Richard Clark, KB7QHC

On Tue, 26 Apr 2005 20:28:01 -0500, Tom Ring
wrote:

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

Hi Tom,

As a second thought, you may not be in the market for the reciprocity
technique (it does require that you have a true reference microphone).

In that case, you would fall back to a Piston Phone and do a single
point calibration. The method is as old as the hills, the math is
extremely simple volumetrics, but the implementation (construction of
the calibration unit) is not something for the faint of heart. You
will need a precision lathe. Again, google using Brüel & Kjær as a
jump-off point.

Once you do the single point calibration, then you can proceed to a
swept frequency analysis. Unfortunately this returns us to the
necessity of a reference microphone. However, as relative frequency
response is more available (from expensive retail models), you might
have a chance.

73's
Richard Clark, KB7QHC

I too am reluctant to enter this as much resembles a freshman poli-sci
student debating a third year law student.

However .... please see indented comments below

--
J. Mc Laughlin; Michigan U.S.A.
Home:

"Reg Edwards" wrote in message
...
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.

OK as far as the statement goes.


The elevation angle is determined purely by trigonometry.

Geometry might have been a better term, but the idea is right.


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.

Here I must inject my experience. As part of a topic sentence, "tends to be
the same" is OK. However, it is common on real HF paths of over 4 or 5 Mm
for the elevation angle at which the strongest signal arrives to be
significantly different at the two ends of the path. It is easy on longer
paths for the major mode at one end to be using a high virtual-height F2
mode and for the other end to be using a low virtual-height E mode.

Allow me to put to rest the notion that optimum elevation angles are
necessarily the same at both ends of a longer (multiple hop) HF path! [Reg
did not say that optimum elevation angle are necessarily the same.]

As other have said, but not all have heard, the idea is to maximize gain
(at both ends of a path) at the elevation angle being used. Even in the
20s, antenna systems were in regular use that attempted to do just this.


Received signal strength depends on the two antenna gains in the
direction of the path.

Agreed. Such an azimuth is not always along a great-circle.

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.

What does exist is a stochastic model of the ionosphere that allows one to
make useful estimates of what is going to happen along a path. As has been
said many times here, all estimates and measurements comprise at least two
numbers: the best estimate and an estimate of the estimate's uncertainty.
Even if it were possible to do so, one would not use an antenna that had all
of its gain at the predicted optimum elevation angle. One would try to
design an antenna (money enters here) that has most of its gain in the
expected band of elevation angles expected to be best for a path.

----
Reg, G4FGQ.



73 Mac N8TT

Well reasoned.

Think of a three-dimensional curve of cost, uncertainty, and frequency to
measure gain on a range. Think of a second 3D curve involving modeling. My
guess is that below something like 20 MHz (use your own number) modeling is
to be preferred.


On a related topic: I saw with my own eyes NBS in Boulder (c. 1978)
using a different technique to measure gain. It was a near field scheme
where a probe was moved in front of the antenna while its vector voltage and
position was measured. (As I recall, a pair of lasers was used in the
measurement of the probe's x and y position.) The (vast number of)
measurements were then imported into a computer that computed the gain. As
we say: "you could do that!" I never thought to ask what the expected
uncertainties were expected to be.
73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Richard Clark" wrote in message
...
On Wed, 27 Apr 2005 03:01:20 +0000 (UTC), "Reg Edwards"
wrote:

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.

Hi Reggie,

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
The errors remain across all applications, only the assigned values
change. If I arbitrarily scaled all values by 25, few could challenge
the numbers.

At 7MHz we can all agree that the errors are going to be inversely
proportional to the astronomical cost to determine. No one is going
to perform it at HF when they can only afford 1/100th scale models
that offer the accuracies implied above. What would spending more
money buy them anyway?

73's
Richard Clark, KB7QHC