Re: Reverberating chambers and screen rooms

1999-05-01 Thread ed . price
Mat:

Every shielded enclosure starts out as a reverberant chamber. You then pay big 
bucks to coat those reflective surfaces with foam or ferrite treatments that 
reduce the reflections.

But you want to shift the three-dimensional peaks and nulls around the volume 
of the chamber. To do this, you have to vary the reflective pattern within the 
room. The easiest way is to get about 3 surplus gearmotors (each with different 
RPM). Mount the gearmotors on the floor or ceiling or a wall of the room. Each 
gearmotor turns a reflective paddle. As the paddles rotate, the pattern 
shifts about the room.

I did a room (12' high by 36' long by 24' wide) where I used one 4'x 8' 
(firring strips with aluminum foil) paddle turning about 6 RPM, one 12 x 18 
(sheet aluminum) paddle turning about 40 RPM, and one 12 x 18 (sheet aluminum 
with the corners bent at odd angles) turning about 60 RPM. During immunity 
testing, I was able to see peak-to-null ratios of about 40 dB in the field 
strength above 1 GHz.

The big problems with the reverberant testing method is time and frequency. You 
really should wait a few minutes at each test frequency to be sure that all 
rotational combinations have been cycled through. This really slows a frequency 
sweep. You usually have to reach some compromise between sweep speed and 
certainty of peak detection. And, the technique becomes less capable as 
frequency drops. In practical size enclosures, I don't think you will get much 
effect below maybe 200 MHz.

For emission testing, I still have some problem grasping the concept of how you 
relate observed emissions to a specific antenna-to-EUT separation distance.

Regards,

Ed



  From: Aschenberg, Mat matt.aschenb...@echostar.com
  Subject: Reverberating chambers and screen rooms
  Date: Fri, 30 Apr 1999 14:36:50 -0600 
  To: 'emc-pstc' emc-p...@ieee.org


 I was wondering how feasible it is to convert a screen room into a
 reverberating chamber? 
 How useful are reverberating chambers in measuring radiated emissions?
 Mat
 
 Mathew Aschenberg 
 
 
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---End of Original Message-

--
Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA.  USA
619-505-2780
List-Post: emc-pstc@listserv.ieee.org
Date: 04/30/1999
Time: 16:13:37
Military  Avionics EMC Services Our Specialty
Also Environmental / Metrology / Reliability
--



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Re: where to buy EMC standards

1999-05-01 Thread glyn . garside

If you have web-access, the FCC regulations (CFR 47) can be downloaded
(free) from both the FCC website WWW.FCC.GOV and the US Government
Printing Office website WWW.GPO.GOV. 

Some ANSI standards (but not C63.4) can be downloaded (if you pay for
them!) from WWW.ANSI.ORG 

Some ISO and other standards can also be purchased  downloaded from
ANSI. You can download a catalog for $10.

Many IEC standards can be downloaded (for a charge) from WWW.IEC.CH -
see below.

The CENELEC website WWW.CENELEC.BE  lists titles, status and (very
useful!) _scope_ of EN standards. But as far as I know, there is no
source for downloading EN standards.

For hard-copies, the IEC website (www.iec.ch) lists National Committees
and other Sales Outlets for most countries. For Singapore, it lists:
 Singapore Productivity and Standards Board (PSB) 
 1 Science Park Drive 
 SG-118221 SINGAPORE 
 TP: +65 279 39 20 
 TF: +65 377 06 69 
 E-Mail: sa...@psb.gov.sg 
 URL: http://www.psb.gov.sg 
  
You should be able to buy some or all ISO, IEC ( CISPR?) standards from
the PSB. I think you can also visit their office to read copies of the
standards.

The IEC standards (now numbered IEC 61000-x-x), and CISPR 22, can also
be bought directly from IEC Web Store (www.iec.ch). Many IEC standards,
including most EMC stds, are available as electronic files for immediate
download (charged to any major credit card). You can also order a
hardcopy to be mailed to you if you prefer. Either way, the price is
quoted in Swiss Francs, check with your bank or a major newpaper for the
current exchange rate. You will get an email confirmation of your irder,
plus a hardcopy receipt will be airmailed to you from Switzerland.

Last time I used this, I had the standard on my computer within 2
minutes, and I printed a hardcopy for myself. The receipt arrived by
airmail 5 days later (Switzerland to USA).

EXTRACT from www.iec.ch:
 .
Buy any of IEC's 4500 (mostly bilingual English/French) publications from
 the IEC Web Store in electronic (PDF) and/or hard-copy versions. Some
 1000 publications are also available in Spanish. Language versions are
 marked in the Search results. Electronic versions (where available) can
 be downloaded immediately or within 5 days of placing the order for use
 on single-user workstations only. Hard-copy versions (all publications)
 will be delivered to your shipping address. 
 Some 1000 IEC publications are now available in Spanish.


PS: You didn't say which countries in Europe, but if you meant the EU or
EEA, I believe officially you should be declaring compliance to the EU-
harmonized versions of the  standards, e.g. EN 61000-x-y etc., not to
the IEC editions. However, I think that the EN 61000-series is identical
in technical content (word for word) with the IEC versions?

You can buy the paper editions of the EN standards from many sources,
in several languages. The English editions can be bought from BSI
(United Kingdom), ANSI (USA) and also from several commercial
distributors, including Global Engineering Documents here in USA (see
earlier replies). I don't know if you can yet buy electronic editions
of any EN standards.

-regards,
Glyn R Garside
Adept Technology, Inc.
(San Jose, California, USA.)
___
Subject: where to buy EMC standards 
From:Qu Pingyu pin...@ime.org.sg  at Internet-Mail
List-Post: emc-pstc@listserv.ieee.org
Date:1999-04-30  09:31

Hello, everyone:

We would like to buy the following EMC standards (US and Europe):

1.  CISPR 22
2.  IEC - 1000 - 1,2,3,4
3.  FCC CFR 47, Vol.1
4.  ANSI C63.4

I suppose that these are the most frequently-used standards in EMC testing.
(Do I miss anything ?). I would appreciate if anybody could tell me where I
can buy these standards. 

Regards

Qu Pingyu


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Correction to details for RMCEMCS May 18 Symposium

1999-05-01 Thread ChasGrasso
Hello:
One minor correction. The cut off date for registration
is May 12th in order to be eligible for the FREE 
continental breakfast and lunch.

Please see our website at 
http://www.ewh.ieee.org/r5/denver/rockymountainemc

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