"Frank" wrote in
news:a5%Ch.98609$Fd.82750@edtnps90:


"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.


Thanks Frank, it is more about summation of field strength measurements
in the real world to a single figure representing max field strength (in
whatever orientation) at that location and frequency.

I was hoping I might find procedures specified by regulatory authorities
for measurement of such... but searching hasn't turned up much.

Owen