Originally Posted by Rick0725
No pissing match is wanted nor is it necessary.
a computer simulation on a controlled test range is the conventional way to test/measure an antenna...like it or not.
unfortunately to my embassassment , it was explained that real world testing of antennas are not considered an accurate means of testing an antenna. Computer simulation on a range is how antennas are to be tested.
what you described in your explanation is exactly why those sorts of tests should be taken with a grain of salt. Any individual any place in the world can put up and test a handful of antennas, under their own "controlled environment" and say one antenna is better than another with their meter. Real world testing as you explain it. Isnt that what we all do here...one way or another.
Antenna analysis is far from an exact science. real world testing does not get you closer...to exact.
ILLR ITM (Individual Location Longley-Rice Irregular Terrain Model) used by
FCC/NTIA, Antennaweb.org, TVFool, Radio Mobile, Splat!, et. al. is a
mix of Line-of-Sight (with ground bounce), Single Knife Edge Diffraction
and Multiple Diffraction models melded into a statistical signal strength
data base (dating back as much as 50-60 years). The stats can vary
quite a bit depending on percentage of Locations and Time you chose:http://www.avsforum.com/avs-vb/attac...0&d=1195561571
The inherent "sigma" is on the order of 6 to 10 dB (or more), depending
on whose comparison report you read last....give or take uncertainties wrt
ground bounce gain, clutter loss, desensitization due to VSWR mismatch,
tree loss, backscatter/sidescatter and other uncertainties.....
I know what an antenna test range test is, e.g. Kerry Cozad's test results:http://www.dielectric.com/broadcast/...ntennas%20.pdfhttps://secure.connect.pbs.org/confe...ns/TC05_43.htm
But results can be significantly influenced by constructive/destructive
effects of the ground bounce component....as you raise/lower antenna to
find the "sweet spot" for each test frequency....
RF absorbing material can suppress ground bounce, but is ineffective at VHF.
[And I doubt ANY was employed in Kerry Cozad's OUTDOOR test range....]
[Indoor RF anechoic chambers for UHF are rather large...and VHF are truly HUGE!!!!]
Or use high TX/RX test locations (e.g. hill top to hill top).
NEC computer simulations (IN FREE SPACE) are typically used to derive
manufacturer's spec sheet data (when they dare to)...and fol. results:www.hdtvprimer.com/antennas/comparing.html
But results are different when the antenna is mounted within a few feet
of your rooftop....or in an attic....or anywhere near other buildings....
Not too mention the simplifications in most of these models.....
I know NEC can be used to model antennas in "real" environments, which
is usually limited to HF band (and maybe a simplified VHF scenario)
due to simulation complexity.
For VHF/UHF you would need to model yours & many of your neighbors roofs,
joist nail plates, plumbing, A/C equipment, interior wiring, antennas,
metal gutters, et. al....whatever diffracts/reflects RF energy....
So what the heck is a "computer simulation on a range"?????
Is it anything like live motion capture animation????
Or a Hybrid mix of reality and computer simuation....like ROGER RABBIT????