I think I see how we may be looking at this from different perspectives.
My cal lab gives me a continuous, swept plot of the response of an antenna. It
also provides me with a tabular listing of that data. There are many more
discrete frequency amplitude pairs plotted to the plot than are listed in the
tabulation. For a biconical, the lab's sweeper is being stepped in 0.05%
frequency steps; typically 50 kHz intervals. However, the typical tabulation
frequency interval is 5 MHz. The tabulation lists only 1 out of 100
measurement points, and these points are chosen arbitrarily, without regard to
"interesting" amplitude changes.
If I were to ignore the plot, and simply enter data from the tabulation sheet,
I could very well miss odd excursions between the tabulation listing points.
Before I actually enter the data into my computer's correction factor file, I
look at the plot to see if there are any more entries I should make between
the tabulation data points. Additions are rare, but sometimes there will be an
inflection point in the plotted curve between the tabulation listings. I will
typically add an additional point for every 0.5 dB amplitude variation, so
sometimes I will add several points between two tabulation listings.
My software accepts a very large number of points in a correction factor file;
I'm not sure of the limit, but I know I have used 200-point files in the past.
Actually, my biggest hassle is that the correction factor file editor is
primitive, and I can't import Excel files (I have to key them in
point-by-point).
Ed Price
ed.pr...@cubic.com <blocked::mailto:ed.pr...@cubic.com> WB6WSN
NARTE Certified EMC Engineer
Electromagnetic Compatibility Lab
Cubic Defense Applications
San Diego, CA USA
858-505-2780
Military & Avionics EMC Is Our Specialty
________________________________
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Luke
Turnbull
Sent: Tuesday, June 09, 2009 3:37 AM
To: Ken Javor; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Measurement Accuracy and antenna factors
An Excel way of picking the relevant points from a large data set is:
1. Put the data into an excel spreadsheet.
2. Copy the data into another spreadsheet that will become the reduced
data
set.
3. Plot the complete and reduced data set on the same graph.
4. Go through deleting rows from the reduced data set, while checking
the
two graphs remain virtually identical.
On another point, it really is best to get a large data set because of
1. The
resonance in a biconical cage without the extra bars. 2. The resonant points
of log periodic antennas, where you can see the effect of each element. A
very good antenna calibration lab may be able to give you a data reduction
that gives the important points, but my experience (from an antenna
calibration lab who would claim to be the best in the UK) is that they
tabulate the data every 10 MHz - and miss the resonant points.
Hope this helps,
Luke Turnbull
Dr Luke Turnbull
EMC Technical Manager
TRW Conekt
Stratford Road
Solihull
West Midlands B90 4GW
Tel: +44 (0)121.627.3966
Mobile: +44 (0)7730.671284
Fax: +44 (0)121.627.4353
email: luke.turnb...@trw.com
web: www.conekt.net
-
This message is from the IEEE Product Safety Engineering Society emc-pstc
discussion list. To post a message to the list, send your e-mail to
<emc-p...@ieee.org>
All emc-pstc postings are archived and searchable on the web at
http://www.ieeecommunities.org/emc-pstc
Graphics (in well-used formats), large files, etc. can be posted to that URL.
Website: http://www.ieee-pses.org/
Instructions: http://listserv.ieee.org/request/user-guide.html
List rules: http://www.ieee-pses.org/listrules.html
For help, send mail to the list administrators:
Scott Douglas <emcp...@ptcnh.net>
Mike Cantwell <mcantw...@ieee.org>
For policy questions, send mail to:
Jim Bacher <j.bac...@ieee.org>
David Heald <dhe...@gmail.com>
