My guess, when an alternate method is provided that isn't 1) so cost
prohibitive that anybody but the largest of companies just say screw it -
let them catch me, or the cost allows many EMC test vendors to have such
equipment rather than a very very few and allow reasonable test scheduling
for the masses of clients., 3) when the problems with the OATS become
insurmountable. 4) When the alternative methods are agreed upon by all.
Personally I love getting into a 10 meter semi-anechoic room and
even pay about a $50.00 premium per hour for it, but I can't always wait the
30 to 60 days to get into it. (Actually a wider range depending on the
telecommunications industry is getting along)
Many will argue that a cheaper 3 meter room doesn't work even if it
did look like free space because of the near/far field problems, some will
argue that the 10 meter rooms still have dissimilarities with OATS below 60
MHz etc.
I'd even have to guess that by standard a 3 meter room would always
be disallowed - at the moment there are provision for moving forward in
distance in both the FCC and CISPR document when in noisy environments. (and
this itself is hotly disputed) but a semi-anechoic chamber could hardly be
described as a noisy environment and this exemption should logically
disappear.
TEM cells at the very best only work with physically small items and
only then with a plethora of problems - three angle rotation, lack of ground
reflection etc.
There may be other options but item 4 will still be a hurdle
Gary
From: Aschenberg, Mat [mailto:[email protected]]
Sent: Thursday, January 29, 2004 7:53 AM
To: 'EMC-PST (E-mail)'
Subject: RE: OATS Measurement
At what point will with EMC community scrap the OATS?
Is appears that the OATS measurement methodology is broken.
When it was designed, there were relatively few intentional radiators, where
as now, the majority of the spectrum is blanketed with ambients.
As a community we have learned a great deal more about radiated emissions
and their measurement technologies. I vote for scraping the OATS and
redesigning the system better.
Why keep band-aiding it?
Mat
Mat Aschenberg
Agency Engineer
EchoStar Technologies Corporation
Englewood, Colorado
(303) 706-5064
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