Field strength - S plane summation
 

Roy Lewallen wrote in
:

Owen Duffy wrote:
Roy Lewallen wrote in news:12tpng510pvr140
@corp.supernews.com:

It's not clear what the objective is. NEC and EZNEC have the ability
to

This is about measurement in the field of emission field strengths,
and techniques for coming up with a single number representing the
emission field strength on a particular frequency at a particular
location.

I understand that, but "representing" in what way -- an average,
weighted average, RMS, probability density, something else? And what
would it mean? Is it supposed to tell how much interference will be
created for the overall community? Will an antenna with a narrow beam
pointing straight up give the same number as one with a narrow beam
pointing horizontally, or are the data for the axes weighted
differently?

Typically, it would the a set of measurements reduced to a descriptor of
centrality and variability, eg median and percentile or inter quartile
range or whatever.

I think it is intended to equate to the field strength that would be
measured using a linearly polarised antenna oriented for maximum pickup.


This is a means of data reduction, in which the result has less
information than the original data. 3D field strength data *does*
represent the emission field strength, but any summation and
consequent reduction represents less information than this.

I'm not saying that industries or the regulatory agencies won't use
something like this to "prove" whatever they need to prove -- but it
should undergo some critical scrutiny to see just what its meaning
really is.

The question comes up in a context of we amateurs measuring and
documenting background noise levels, and whether the z, y, z - S is
better than just swinging a loop for maximum response and recording the
measurement.

I am of the view that the three dimensional measurement is really a
technique suited to automated measurement of a large set of frequencies
with and instrument that has a single plane antenna that it cannot re-
orient, and whilst it addresses that issue, it is unnecessary
complication for a hand held loop that can be maximised.

But, my opinons are not very important, I am interested in any formal
testing procedures, and the opions of other knowledgeable and experience
practitioners like yourself Roy.


After all, half the children in the schools are below average!

Not necessarily, it depends on the population distribution, doesn't it?
Exactly half would be less than the median, provided there were an odd
number of children.

Pickiness over averages aside, your comments are appreciated Roy.

Owen

Field strength - S plane summation
 

On Feb 21, 12:43 pm, "Jimmie D" wrote:
"Owen Duffy" wrote in message

...



I am looking for reference information for summation of field strength
measurements in x, z and z planes to the so called s-plane summation.

Does anyone have any pointers?

Thanks
Owen

The only time I have ever heard reference to this it had to deal with
measureing the field strength of the far field beam of a radar antenna. Its
been a while but I am pretty sure it had something to do with checking out a
polarizer for proper operation when it was switched from linear to
circular..

Jimmie

Also pretty sure the S was refered to as SIGMA, maybe this will help.

Jimmie

Field strength - S plane summation
 

Owen Duffy wrote:
Roy Lewallen wrote in
:

Owen Duffy wrote:
. . .
After all, half the children in the schools are below average!

Not necessarily, it depends on the population distribution, doesn't it?
Exactly half would be less than the median, provided there were an odd
number of children.
. . .

And right you are -- I stand corrected.

Guess I was blinded by thinking of the statistician who drowned crossing
a creek which had an average depth of only three feet.

Roy Lewallen, W7EL

Field strength - S plane summation
 

Roy Lewallen wrote in news:12tqej81j7cb317
@corp.supernews.com:

Owen Duffy wrote:
Roy Lewallen wrote in
:

Guess I was blinded by thinking of the statistician who drowned crossing
a creek which had an average depth of only three feet.

Thanks Roy, I must remember that. It is a salutory reminder that the value
of an average (or a median for that matter) may be limited.

Owen

Field strength - S plane summation
 

After all, half the children in the schools are below average!

No, no, no, never. Just ask the parents, the school boards, the principals,
and the kids. At least 95% are above average. Using a 4-point system (A=4
and so forth) they graduate with averages above 4.0 and with multiple
valedictorians (so no one will be hurt).

Bill - W2WO

Field strength - S plane summation
 

On Thu, 22 Feb 2007 02:53:12 GMT, Owen Duffy wrote:

I am of the view that the three dimensional measurement is really a
technique suited to automated measurement of a large set of frequencies
with and instrument that has a single plane antenna that it cannot re-
orient, and whilst it addresses that issue, it is unnecessary
complication for a hand held loop that can be maximised.

Hi Owen,

It sounds like you want a Black Body Absorber.

You might want to take your lead from that if you are building
instrumentation (the purpose of your data reduction).

Presumably you would also want it to be isotropic in sensitivity. If
my speculations are correct, the simplest method would be caloric
based, but the trick would be to get it to occupy a volume of space
AND present 377 Ohms; but then how would you shade if from the sun
(another notable field presence that would innundate your detector);
or if done at night, how would you cope with the infinite heat sink in
nearly half the field of view? Most caloric methods employ a bridge
configuration that balances out these disturbances.

So, the simplest method is not very simple at all. Compare it to the
more difficult methods and you may wish for it after-all.

73's
Richard Clark, KB7QHC