Gentlemen,
What would you consider the drawbacks of using a 3 Meter limited
height chamber (10x10x22 FT) for pre-scan to FCC & EN (ANSI C63.4) and
immunity testing (EN50083-2 A1) My company will not spend the money
for a 10 Meter full height chamber.
As for node stirring, I have used wire screens to tune an indoor OATS
site to reduce reflections. But I can see how wire screen or absorber
tied to a celling fan might work in a chamber. Interesting.
Al Patrick
Scientific-Atlanta
EMC Pre-Scan Lab Engineering Manager
[email protected]
______________________________ Reply Separator
_________________________________
Subject: RE: Indoor vs. Outdoor emissions testing
Author: "Flinders; Randall" [SMTP:[email protected]] at IMS
List-Post: [email protected]
Date: 10-28-98 5:31 PM
Does anyone have any experience with mode sturring as a method to improve
the
low frequency performance of test chambers?
Regards,
Randy Flinders
EMC Engineer
Emulex Network Systems
(714) 513-8012
[email protected]
----------
From: Gordon Andrews
Sent: Wednesday, October 28, 1998 11:09 AM
To: [email protected]
Subject: Re: Indoor vs. Outdoor emissions testing
10 meter chambers can and will become resonate somewhere below 80MHz if
they are not large enough. In order to make them large enough to avoid
this problem you must build a building taller than most buildings to contain
it!
I previously worked at a company where we did not trust measurements in that
range.
They had a quiet open site like yours which was accurate.
> From: "Steve Kuiper" <[email protected]>
> To: "EMC-PSTC" <[email protected]>
> Subject: Indoor vs. Outdoor emissions testing
> Date: Tue, 27 Oct 1998 12:31:59 -0800
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> Joe,
>
> Our laboratory was used to compare readings in the low-end, specifically
30
> MHz. to 90 MHz. on an OEM product In particular the OEM customer who
> maintains 10m indoor anechoic facilities claimed that our customer was
> failing the CISPR22B limits by 5-6dB in the above freq. range. After
taking
> our own readings and comparisions with 3 different OATS in a 1.5 day
> turnaround we showed a 1.8 - 2.5 dB correlation between the OATS!!!!!! The
> meter reading at all three sites indicated a passing margin of 3-4dB using
> the identical product and configuration previously tested in the Anehoic
> Chamber. All OATS test sites used contained different test, equipment,
> ground structure, ambients. etc. Of course only 3 or 4 frequencies were
> observed for this comparison but we found our OATS correllation from site
to
> site to be extremely good in this case.
>
> In my opinion, for engineering purposes only the 10m chamber is ideally
> suited for accomplishing the task of high volume testing. Zero ambients,
> and automated testing is the only way to fly. However, with all the
> improving absorber technology as such I still believe for correlation and
> repeatability there is no equal to the 10m OATS, especially for those
> located in a low ambient environment. Our faclity is located deep within
a
> canyon at the base of a 4000 foot mountain in So. Cal near a creek bed.
The
> floor noise is excellent and the ambients are low. Line noise is
> non-existent. Our customers see many advantages.
>
> Hope this helps.
>
> Regards,
> SJK
>
>
>
>
>
>
>
>
>
>
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_/_/_/ _/ _/ _/ _/ Gordon Andrews
_/ _/ _/ _/_/ _/ EMC Compliance Technician
_/_/_/ _/ _/ _/ _/ _/ Office/Voice Mail:(650)-786-3899
_/ _/ _/ _/ _/_/ Email:[email protected]
_/_/_/ _/_/_/ _/ _/
M I C R O S Y S T E M S
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