"chuck" wrote in message
...
Owen Duffy wrote:
Roy Lewallen wrote in
:
Maybe the lack of responses is because of the obscurity of the
"s-plane summation". I've never heard of it, and a web search brought
only one or two possible hits from publications I'd have to buy in
order to view. Any principle with that low a profile on the web is
pretty esoteric.
Roy Lewallen, W7EL


Roy, to kick it along a little...

The technique calls for making sets of measurements with the antenna in
three orthogonal orientations and summing the z, y and z plane values to
an "s plane" value to represent maximum field strength. I think the
summation that is typically used is the square root of the sum of the
squares. The technique suits automated measurement where a series of
perhaps
hundreds of measurements at different frequencies are made, the antenna
is manually changed, and the series repeated etc. Software is then used
to process the logged measurements. Clearly there is an issue about the
temporaral nature of separate
measurements in each plane at a given frequency.

Well, if the field is changing in an unknown way, measurements at x, y,
and z axes at different times would be meaningless of course.

I was interested in any standards or regulatory "procedures" that may
exist that describe / mandate such technique. Most procedures that I
have found just call for orienting the antenna for maximum response
rather than the x,z,z trick.
Calculation of the resultant for a static field is not really a trick. In
the absence of a triaxial instrument, that may be the only practical
technique available.

I would like to understand its application better to for a view about
the appropriateness to particular applications. I suspect its main value
is in automated EMC data capture.

You are talking about simply calculating the resultant of three orthogonal
vectors. Not an esoteric technique. Its main value is in making a
measurement without a triaxial instrument. Or, alternatively, positioning
a single-axis instrument for maximum reading and then measuring the
position coordinates of the instrument's axis.

Many triaxial instruments have three orthogonal probes and calculate and
display the resultant automatically. Three orthogonal measurements
separated in time and requiring separate calculation of the resultant is a
move away from automation and accuracy, I would think.

You might search instead for discussions on measuring static magnetic
fields with single-axis gaussmeters. Inexpensive gaussmeters are commonly
used in this manner. I get ~350K results in a google search on "triaxial
field measurement."

Owen,

Where, I guess, "S" is the Poynting vector? I have made attempts at
estimating
the TRP from a NEC output file -- including the ground wave. The results
appear to be reasonably correct, but have no means of verifying the results.
If I am on the right track I can send you my Excel spread sheet clearly
showing
the method I used. I did the analysis for Reg in order to compute the true
radiation resistance of a ground mounted monopole. I have a MathCAD 7
document, which also shows the method I used, and is probably easier to
interpret.

73,

Frank