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January 31st 04, 08:04 PM

On 31 Jan 2004 07:42:00 -0800, (Maurizio) wrote:

However, the antenna that was simulated in the paper I was talking
about is a real antenna that has been modellized with a dedicated MOM
program and with the correct antenna geomety, and results have been
compared with measurements.
From this comparison it has been necessary the introduction of such
factor.
It seems to me that the 6 dB factor had to take into account all
losses from the transmitter to the radiated fields.
My concern is how this factor can be justified.
6 dB is a lot in terms of antenna usefull coverage distance.

Maurizio

Hi Maurizio,

I am a trained Metrologist with advanced studies in Microwaves. The
measure of power (which is intimately tied to any expression of dB) is
very difficult to achieve with great accuracy. This means that
measurements are always suspect when they purport to confound theory.

The logic of the MOM program that works at one wavelength expresses
that it will work at all wavelengths. There is no scale determinacy
whereby results in HF are corrupted in SHF. There is every potential
for human error and measuring power reveals that quicker than any
other effort.

A 6dB discrepancy is a human problem, and glaringly evident.

73's
Richard Clark, KB7QHC

February 4th 04, 08:36 AM

Richard Clark wrote in message . ..
On 31 Jan 2004 07:42:00 -0800, (Maurizio) wrote:

However, the antenna that was simulated in the paper I was talking
about is a real antenna that has been modellized with a dedicated MOM
program and with the correct antenna geomety, and results have been
compared with measurements.
From this comparison it has been necessary the introduction of such
factor.
It seems to me that the 6 dB factor had to take into account all
losses from the transmitter to the radiated fields.
My concern is how this factor can be justified.
6 dB is a lot in terms of antenna usefull coverage distance.

Maurizio

Hi Maurizio,

I am a trained Metrologist with advanced studies in Microwaves. The
measure of power (which is intimately tied to any expression of dB) is
very difficult to achieve with great accuracy. This means that
measurements are always suspect when they purport to confound theory.

The logic of the MOM program that works at one wavelength expresses
that it will work at all wavelengths. There is no scale determinacy
whereby results in HF are corrupted in SHF. There is every potential
for human error and measuring power reveals that quicker than any
other effort.

A 6dB discrepancy is a human problem, and glaringly evident.

73's
Richard Clark, KB7QHC

Hi Richard,
I agree that the human factor can be the problem for this discrepancy,
however, it would be also very interesting to know about other
experiences with such type of measurements, just to narrow the
expected uncertainty window.
(Better if in presence of complex environments)

Maurizio

February 4th 04, 08:56 PM

On 4 Feb 2004 00:36:07 -0800, (Maurizio) wrote:

A 6dB discrepancy is a human problem, and glaringly evident.

73's
Richard Clark, KB7QHC

Hi Richard,
I agree that the human factor can be the problem for this discrepancy,
however, it would be also very interesting to know about other
experiences with such type of measurements, just to narrow the
expected uncertainty window.
(Better if in presence of complex environments)

Maurizio

Hi Maurizio,

This is best achieved by establishing a standard with as few variables
as possible, then varying them to determine their range of error
contribution. I am sure this is already evident to you, however
experience in going through the tests can reveal how probable those
sources of error may be.

You can quickly accumulate 3dB error in simply not providing the
correct load to the power (dB) determining measurement. Temperature
too can upset readings, but often as not, the simple presence of the
observer disrupts many things. The source is all to often taken for
granted, and all too often has frequency products that add to the
power reading, but are not in the bandwidth of interest. The list
goes on....

73's
Richard Clark, KB7QHC

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