wrote:

snip

Whow, thats a good idea, write it up for QST. They are looking for pearls of
wisdom
that can be useful for ham radio operators so that we may maintain our
perceived
leadership of the art of antennas......'Compare with a antenna of known
gain'...... Revolutionary!
Now why hasn't any Guru on this group thought of this before today?
Now we have to decide what we use to measure the gain and more important
not to compare or to compare at a single recieving point especially if the
snip

This is a rhetorical question -

Do you actually read the posts in this group which are related to
antennas? Other than your own, that is.

tom
K0TAR

wrote:
"Richard Harrison" wrote in message
...

Reg, G4FGQ wrote:
"Naturally, laboratories can differ one from another."

A lab may put its stamp of approval on your instrument, but your best
assurance may be measurement of known values. The temperature of
ice-water or the voltage of new dry cells, for example You usually can
try several dry cells for confirmation or averaging.

In antennas, one strategy for successful gain determination is
comparison with an antenna of known gain.


Whow, thats a good idea, write it up for QST. They are looking for pearls of
wisdom that can be useful for ham radio operators so that we may maintain our
perceived leadership of the art of antennas......'Compare with a antenna of known
gain'...... Revolutionary!
Now why hasn't any Guru on this group thought of this before today?

rest snipped

Well Art, as much as people may desire some sort of definitive "this
antenna performs exactly as....." statements, it would seem that they
aren't going to get them.

Which is to say that Richard's statement IS a pearl of wisdom, despite
being unsatisfactory in some peoples view.

- Mike KB3EIA -

"Mike Coslo" wrote in message
...
wrote:
"Richard Harrison" wrote in message
...

Reg, G4FGQ wrote:
"Naturally, laboratories can differ one from another."

A lab may put its stamp of approval on your instrument, but your best
assurance may be measurement of known values. The temperature of
ice-water or the voltage of new dry cells, for example You usually can
try several dry cells for confirmation or averaging.

In antennas, one strategy for successful gain determination is
comparison with an antenna of known gain.


Whow, thats a good idea, write it up for QST. They are looking for pearls
of wisdom that can be useful for ham radio operators so that we may
maintain our perceived leadership of the art of antennas......'Compare
with a antenna of known gain'...... Revolutionary!
Now why hasn't any Guru on this group thought of this before today?

rest snipped

Well Art, as much as people may desire some sort of definitive "this
antenna performs exactly as....." statements, it would seem that they
aren't going to get them.

Which is to say that Richard's statement IS a pearl of wisdom, despite
being unsatisfactory in some peoples view.

Mike,
Do you really believe that Reg is really unaware that "comparing
with a dipole" can be used by some (as long as all parameters are stated
specific and to the point) ? If Richard really thought that comparing to a
dipole was unique
Richard surely should have added more data. Thus the reason that Richard
brought forth
this item of wisdom forward in answer to Reg,s initial post, which was quite
clear,
is unfathomable without a "grin" additive to declare his true intent was not
to be facitious.
Especially since it did not add details which pertained to professional
antenna.
measurement methods as requested by Reg which is part and parcel of
ascertaining
degree of error that was specifically referred to.
As an aside it would appear that statements above made by Richard have been
atributed to Reg which certainly muddies the waters to which you refer to.
Regards
Art
..
Regards
Art


- Mike KB3EIA -

Art Unwin wrote:
"If Richard really thpoght that comparing to a dipole was unique."

Not at all. I was relating an experience which I hoped was accurate and
useful.

Kraus describes the "comparison method" on page 857 of his 3rd edition
of "Antennas". I used the reverse of his example, switching transmitting
antennas instead of receiving antennas.

Kraus` volume goes into many details of antenna testing.

Best regards, Richard Harrison, KB5WZI

On Sun, 24 Apr 2005 19:38:10 GMT, "
wrote:

|
|"Richard Harrison" wrote in message
...
| Reg, G4FGQ wrote:
| "Naturally, laboratories can differ one from another."
|
| A lab may put its stamp of approval on your instrument, but your best
| assurance may be measurement of known values. The temperature of
| ice-water or the voltage of new dry cells, for example You usually can
| try several dry cells for confirmation or averaging.
|
| In antennas, one strategy for successful gain determination is
| comparison with an antenna of known gain.
|
|Whow, thats a good idea, write it up for QST. They are looking for pearls of
|wisdom
|that can be useful for ham radio operators so that we may maintain our
|perceived
|leadership of the art of antennas......'Compare with a antenna of known
|gain'...... Revolutionary!
|Now why hasn't any Guru on this group thought of this before today?

Perhaps because it's so commonplace that it doesn't bear mentioning.

|Now we have to decide what we use to measure the gain and more important
|not to compare or to compare at a single recieving point especially if the
|receiving depends
| on skip or propagation. Is it possible that Guru's are unaware that
|elevation angles
|can be different when comparing antennas? Another gem for the ARRL and
|provided
|solely by the leading gurus of AMATEUR radio operators no less. Ofcourse we
|need
|a telephone link with the country that we wish to hear the transmission,
|some thing on the simple lines of
|...."can you hear me now"
| question as we switch antennas
|between a dipole and a drape / curtain array every 5 minutes

If you believe that precision antenna gain measurements are made under
ionospheric propagation conditions, you are clearly delusional. But I
repeat myself.

"Wes Stewart" *n7ws*@ yahoo.com wrote in message
...
On Sun, 24 Apr 2005 19:38:10 GMT, "
wrote:

|
|"Richard Harrison" wrote in message
...
| Reg, G4FGQ wrote:
| "Naturally, laboratories can differ one from another."
|
| A lab may put its stamp of approval on your instrument, but your best
| assurance may be measurement of known values. The temperature of
| ice-water or the voltage of new dry cells, for example You usually can
| try several dry cells for confirmation or averaging.
|
| In antennas, one strategy for successful gain determination is
| comparison with an antenna of known gain.
|
|Whow, thats a good idea, write it up for QST. They are looking for pearls
of
|wisdom
|that can be useful for ham radio operators so that we may maintain our
|perceived
|leadership of the art of antennas......'Compare with a antenna of known
|gain'...... Revolutionary!
|Now why hasn't any Guru on this group thought of this before today?

Perhaps because it's so commonplace that it doesn't bear mentioning.



That's what I thought. So why did Richard say it unless he felt that Reg's
education in antennas was a bit lacking. Reg's question was specific and of
high caliber
Richard's answer tried to bring it down to a level for dummies which did
not begin
to reflect on the question posed



|Now we have to decide what we use to measure the gain and more important
|not to compare or to compare at a single recieving point especially if
the
|receiving depends
| on skip or propagation. Is it possible that Guru's are unaware that
|elevation angles
|can be different when comparing antennas? Another gem for the ARRL and
|provided
|solely by the leading gurus of AMATEUR radio operators no less. Ofcourse
we
|need
|a telephone link with the country that we wish to hear the transmission,
|some thing on the simple lines of
|...."can you hear me now"
| question as we switch antennas
|between a dipole and a drape / curtain array every 5 minutes

If

Yes ,,,a big "IF" isn't it?
But you could supply the info Reg was looking for since you
perceive yourself as a GURU .
It would be much more rewarding to the group as a whole than
picking out somebody to demean.My point is that a gain figure alone
is meaningless unless the elevation angle differences or perhaps a
3 dB window comparison are also supplied.
If you think otherwise I would welcome a technical response
rather than something lead by emotion

Art



you believe that precision antenna gain measurements are made under
ionospheric propagation conditions, you are clearly delusional. But I
repeat myself.

Art Unwin wrote:
"My point is that again figure alone is meaningless unless the elevation
angle differences or perhaps a 3 dB window comparison are also
supplied."

Reg knows very well that a quantity is determined by comparing it with a
known standard.

The power gain of a resonant dipole in free-space is given by Terman on
page 871 of his 1955 edition as 1.64.

Kraus agrees on page 54 of his 1950 edition and converts Terman`s power
gain of 1.64 to 2.14 dB (referenced to an isotropic).

The values given by Terman and Kraus are accepted.

Horizontal antennas at the same heights tend to have similar elevation
angles, but even if they didn`t, comparison of the signals our two
antennas laid on the target represented our interest in the matter.

What we confirmed was that the new curtain antenna had a gain comparable
with our rhombics but over a wider beamwidth which meant listeners on
the edges of our coverage got a better signal with the new curtain
antenna.

The bandwidth was less than a phombic so the curtain meant more work for
the operators, but the broadcasts were for the listeners` benefit.

Signal strengths were measured at many locations around the target area
to define the coverage of the antenna pattern.

Best regards, Richard Harrison, KB5WZI

To determine the gain of a SW BC curtain antenna, we hung a 3-wire
(to
match 600-ohms) folded dipole alongside and at the same height as
the
curtain. We swiched transmission back and forth every 5 minutes
between
the dipole and the curtain. We continuously measured and recorded
the
signal strength for several days in the target area. We averaged
strengths of each signal and compared them for periods of the
recordings.

The HF dBd of the curtain agreed very well with that measured on the
model at 400 MHz in the lab before the curtain was built at full
scale.

Best regards, Richard Harrison, KB5WZI

==================================

Richard, fine, so that was the measurement procedure. Thanks for the
description.

Now all we want to know is what was the uncertainty in the
measurement.

Was it within plus or minus x percent? Or perhaps plus or minus y
decibels?

Can you remember the uncertainty approximately?

Or perhaps it didn't matter what the uncertainty was. In which case
it was a waste of time making the measurement.
----
Reg, G4FGQ

Reg, G4FGQ wrote:
"Or perhaps it didn`t matter what the uncertainty was."

Examination of the comparative feild strength data left no doubt that
the antenna was working as expected. This was the first of several
similar antennas to be constructed. Before proceeding we needed
verification of the design and construction.. It worked and we built
more.

Best regards, Richard Harrison, KB5WZI

Richard,
You state that you used a dipole to compare with, which was at the same
height !.
Which antenna was altered so that the elevation angle of maximum gain
was the same for both antennas.such that max gain measurements
were truly comparable?
Where was the height of the "curtain" measured or referred to
so that "same height" could be justified ?
( You also did say it was for SW use which is certainly different
to ground wave use)
Presumably, the comparison was for the same type of polarization
and ignored differences created by the side addition of other
types of polarization.
Without further information the "Facts" could be seen as
correct to plus or minus 100 percent measurement error!
An expert in the field of measurements such as Richard could have a field
day
disecting the test mode as discussed by you and certainly does not reflect
the
professional antenna analysis aproach which Reg is seeking., which, most
certainly,
would take into account the elevation angle at which maximum gain occurs
as well as many other things

Art




"Richard Harrison" wrote in message
...
Reg, G4FGQ wrote:
"Or perhaps it didn`t matter what the uncertainty was."

Examination of the comparative feild strength data left no doubt that
the antenna was working as expected. This was the first of several
similar antennas to be constructed. Before proceeding we needed
verification of the design and construction.. It worked and we built
more.

Best regards, Richard Harrison, KB5WZI