Data from a 3m chamber has been used for over 20 years for FCC Class A
requirements. It used to meet the NSA with two antennas/masts so 30-200 and
200-1000 MHz could be done at the same time. I hear that the first 3m chamber
qualified to do that may be for sale by Florida Atlantic University in Boca
Raton, FL.
- Bill
You can say what you want about the South, but you never hear of anyone
retiring and moving North!!!
--- On Thu, 7/31/08, pat.law...@slpower.com <pat.law...@slpower.com> wrote:
From: pat.law...@slpower.com <pat.law...@slpower.com>
Subject: Re: Class A antenna distance
To: emc-p...@ieee.org, emcp...@aol.com
Date: Thursday, July 31, 2008, 12:29 PM
Listmembers,
The original poster wrote:
> I have a question on the use of a 3 meter fully anechoic chamber.
>
> Can this 3 meter chamber be used to qualify a product for FCC or CISPR
> class A, since the required test distance is 10 meter?
I thought another clause in FCC Part 15 was important, too. Clause
15.31(d)
says:
(d) Field strength measurements shall be made, to the extent possible,
on an
open field site. Test sites other than open field sites may be employed if
they are properly calibrated so that the measurement results correspond to
what would be obtained from an open field site.
<snip remainder of clause>
Is it practical to get corresponding measurements in a 3m semi-anechoic
chamber, let alone a fully-anechoic chamber?
Pat Lawler
EMC Engineer
SL Power Electronics Corp.
emc-p...@ieee.org wrote on 07/30/2008 02:51:01 PM:
> Since were in the process of buying 5m chamber this thread caught my
eye.
>
> I checked with the FCC, and they point to this paragraph in part
15.31:
>
> (f) To the extent practicable, the device under test shall be measured
> at the distance specified in
> the appropriate rule section. The distance specified corresponds to
the
> horizontal distance between the
> measurement antenna and the closest point of the equipment under test,
> support equipment or
> interconnecting cables as determined by the boundary defined by an
> imaginary straight line periphery
> describing a simple geometric configuration enclosing the system
> containing the equipment under test.
> The equipment under test, support equipment and any interconnecting
> cables shall be included within this
> boundary.
> (1) At frequencies at or above 30 MHz, measurements may be performed
at
> a distance
> other than what is specified provided: measurements are not made in
the
> near field except where it can be
> shown that near field measurements are appropriate due to the
> characteristics of the device; and it can be
> demonstrated that the signal levels needed to be measured at the
> distance employed can be detected by the
> measurement equipment. Measurements shall not be performed at a
distance
> greater than 30 meters
> unless it can be further demonstrated that measurements at a distance
of
> 30 meters or less are impractical.
> When performing measurements at a distance other than that specified,
> the results shall be extrapolated
> to the specified distance using an extrapolation factor of 20
dB/decade
> (inverse linear-distance for field
> strength measurements; inverse-linear-distance-squared for power
density
> measurements).
> I would be very concerned if requirements were written that said only
10
> metre chambers or OATS were acceptable...
> Best regards,
> Derek Walton
> L F Research
>
> Bill Stumpf wrote:
> > Both answers are correct, but also the term Fully Anechoic Chamber
> > raises a flag. The FCC does not allow the use of fully anechoic
> > chambers for emissions testing (30MHz - 1000MHz). Reference ANSI
> > C63.4(2003) Section 5.
> >
> > CISPR 22 does not allow the use of fully anechoic chambers (Section
> > 10.4) & (CISPR 16.1.4)
> >
> > All test sites must meet vertical and horizontal theoretical Site
> > Attenuation.
> >
> > Bill Stumpf
> >
------------------------------------------------------------------------
> > *From:* emc-p...@ieee.org [mailto:emc-p...@ieee.org] *On Behalf Of
> > *Pettit, Ghery
> > *Sent:* Wednesday, July 30, 2008 2:06 PM
> > *To:* Rudd, Adam; emcp...@aol.com; emc-p...@ieee.org
> > *Subject:* RE: Class A antenna distance
> >
> > Note that the allowance for shorter measurement distances in CISPR
22
> > is for small devices, too. And, as noted, is limited to Class B
> > devices. Plus, some regulators do not allow this option to be used
> > and insist on 10 meter data.
> >
> >
> >
> > Ghery Pettit
> >
> >
> >
> >
> >
> >
------------------------------------------------------------------------
> >
> > *From:* emc-p...@ieee.org [mailto:emc-p...@ieee.org] *On Behalf Of
> > *Rudd, Adam
> > *Sent:* Wednesday, July 30, 2008 11:59 AM
> > *To:* emcp...@aol.com; emc-p...@ieee.org
> > *Subject:* RE: Class A antenna distance
> >
> >
> >
> > 47CFR 15.31(f)(1) allows measurements at distances other than
> > specified and details the extrapolation factor.
> >
> > http://edocket.access.gpo.gov/cfr_2007/octqtr/47cfr15.31.htm
> >
> >
> >
> > EN 55022 Section 10.2.1 has a note that specifically makes an
> > allowance for Class B devices to be measured at 3m. I tend to think
> > the detail of Class B being included and Class A being omitted from
> > the note has significance.
> >
> > *Best Regards,*
> >
> > *Adam Rudd*
> > Engineer (EMC)
> > NCR Corporation, RHSS
> > Duluth, GA
> > (770) 495-2825
> >
> >
------------------------------------------------------------------------
> >
> > *From:* emc-p...@ieee.org [mailto:emc-p...@ieee.org] *On Behalf Of
> > *emcp...@aol.com
> > *Sent:* Wednesday, July 30, 2008 2:26 PM
> > *To:* emc-p...@ieee.org
> > *Subject:* (no subject)
> >
> >
> >
> > Dear members,
> >
> >
> >
> > I have a question on the use of a 3 meter fully anechoic chamber.
> >
> >
> >
> > Can this 3 meter chamber be used to qualify a product for FCC or
CISPR
> > class A, since the required test distance is 10 meter?
> >
> >
> >
> > Please provide any reference to paragraphs in the standards. Your
> > responses are appreciated.
> >
> >
> >
> > Thanks,
> >
> >
> >
> > Timothy A. Pierce
> >
> > Tap Engineering, Inc.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
------------------------------------------------------------------------
> >
> > Get fantasy football with free live scoring. Sign up for FanHouse
> > Fantasy Football today
> > <http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020>.
> >
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