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

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

"Richard Harrison" wrote
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.

"Propagation" has to include ALL means by which EM energy radiated from a
wire antenna finally arrives at a receiving location. That necessarily
includes the radiation effects of reflecting/obstructing objects and
surfaces, each of which may be illuminated by varying ERP from the wire
antenna -- depending on the radiation envelope of the wire antenna itself,
its installation detail, and site topology.

The ERP directed toward a particular receiving site depends on more than the
free space gain of the tx antenna along a single launch angle (which I
believe is Art's point).

RF

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

"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).

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. 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).

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.

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

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

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 Mon, 25 Apr 2005 14:48:38 -0700, Wes Stewart
wrote:

It may come as a surprise to our correspondent who likes to disparage
"gurus" that "standard-gain" antennas are widely used as reference
standards. To head off the question of how the standard gain is
determined, that is done by testing three "identical" antennas in
pairs; each one against the other two, with one the source and the
other the receiver. A bit of algebra and you have the gain of each
one individually.

http://www.mi-technologies.com/literature/a00-044.pdf


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).

As an aside, this method is also as old as the pyramids - literally.
The Egyptians planned their blocks of granite to have nearly flat
faces to within 10s of microinches using three blocks, by abrading one
against the other and then rotating their positions.

Accuracy is far more a matter of protocol or technique than it is
about a ruler (or other scale).

73's
Richard Clark, KB7QHC

On Tue, 26 Apr 2005 00:04:02 -0700, Richard Clark
wrote:

On Mon, 25 Apr 2005 14:48:38 -0700, Wes Stewart
wrote:

It may come as a surprise to our correspondent who likes to disparage
"gurus" that "standard-gain" antennas are widely used as reference
standards. To head off the question of how the standard gain is
determined, that is done by testing three "identical" antennas in
pairs; each one against the other two, with one the source and the
other the receiver. A bit of algebra and you have the gain of each
one individually.

http://www.mi-technologies.com/literature/a00-044.pdf


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).

It is also a method used for determining the phase noise of low noise
oscillators.


As an aside, this method is also as old as the pyramids - literally.
The Egyptians planned their blocks of granite to have nearly flat
faces to within 10s of microinches using three blocks, by abrading one
against the other and then rotating their positions.

Accuracy is far more a matter of protocol or technique than it is
about a ruler (or other scale).

73's
Richard Clark, KB7QHC

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