Andrew,
Under "Radiated emission limits" for unintentional radiators, FCC 47 CFR
Part 15 (July 10, 2008 version at
http://www.fcc.gov/oet/info/rules/part15/PART15_07-10-08.pdf )
Paragraph 15.109(g) permits Radiated Emissions testing to CISPR 22--
specifically CISPR 22:1997 Third Edition (Paragraph 15.38(b)(11)):
"As an alternative to the radiated emission limits shown in
paragraphs (a) and (b) of this section, digital devices may be shown
to comply with the standards contained in Third Edition of the
International Special Committee on Radio Interference (CISPR), Pub.
22, “Information Technology Equipment - Radio Disturbance
Characteristics - Limits and Methods of Measurement” (incorporated by
reference, see § 15.38)."
Paragraphs 15.109(g)(1) through (4) go into more detail.
Under "Conducted limits" for unintentional radiators, Section 15.107
has the exact same conducted limits on AC power as CISPR 22:1997. For
some period before then, we could use the:
* FCC conducted limits, which covered 450kHz to 30MHz.
OR
* CISPR 22 conducted limits, which cover 150kHz to 30MHz.
Two advantages of testing unintentional radiators to the CISPR 22 limits
are:
* These tests simultaneously satisfy Canada's ICES-003 Issue 4 "Digital
Apparatus"
http://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/ices003e.pdf/$FILE/
ices003e.pdf
specifically Paragraph 7.1, so we don't have to run separare tests
on 110V 60Hz products for the US and Canada.
* We don't get "surprised" by a noise spike exceeding a limit
because we moved from a 3m measuring distance to a 10m measuring
distance, or vice versa. Lexmark calls this correction to 1/r
rolloff (Maxwell's Equations, in the far-field at r > lambda/2*pi)
the "vertical correction factor", because it mainly affects
vertical polarization-- it can throw us off by up to 7dB around
200MHz.
Thanks!
John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, SM IEEE
dBi Corporation
216 Hillsboro Ave
Lexington, KY 40511-2105
(859)253-1178 phone
(859)252-6128 fax
[email protected]
http://www.dbicorporation.com/
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