Created 2-21-2004 14:30 UTC Updated 2-22-2004 04:05 UTC

Examining the 'sham' that is EMI/RFI compliance

Examining the 'sham' that is EMI/RFI compliance by maufacturers of the *new* lightweight switchmode battery chargers.

This 'sham' involves manufacturers classifying their product as a 'Class A Digital Device' and simply meeting the HIGHER limits for EMI rather than the more restrictive 'default' limits for unintentional radiators. Here is a typical "EMC" notice found on a Guest Model 2623 Battery Charger:

Exploring this sham will require a short trip into "FCC Rules and Regulations" as they are called. The FCC's 'rules and regs' are located in Title 47 of the Code of Federal Regulations. The Office of Engineering and Technology (abbreviated "OET") is responsible for the maintenance of FCC rules located in Parts 2, 5, 15, and 18 of Title 47. The text excerpted and annotated below are from the relevant FCC rules and regulations covering so-called "Part 15 devices" as obtained from these sources:

The FCC Homepage for the FCC's Office of Engineering and Technology (OET):

The FCC's OET Part 15 Rules (in pdf format) from the FCC's own website (seems to have the most up-to-date version):

The FCC's OET rules available via the Federal Register web site:

FCC Rules and Regs Part 90 (Private Land Mobile), Part 95 (Personal radio services A/K/A CB, MURS, PRS) and Part 97 (Amateur radio service) can be found here on the Federal Register web site: 







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    Editor's note:

    CFR Title 47 Chapter I, Part 2, Section 2.801 (excerpt shown below) defines a 
    "radiofrequency device" and Section 2.803 declares the conditions and testing
    under which these devices may be sold to the public.

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47 CFR Ch. I (10–1–01 Edition)

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 2 -- FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS

Subpart I—Marketing of Radiofrequency Devices

SOURCE: 35 FR 7898, May 22, 1970, unless otherwise noted.

§ 2.801 Radiofrequency device defined.

As used in this part, a radiofrequency device is any device which in its operation is capable of emitting radiofrequency energy by radiation, conduction, or other means. Radiofrequency devices include, but are not limited to:

(a) The various types of radio communication transmitting devices described throughout this chapter.

(b) The incidental, unintentional and intentional radiators defined in part 15 of this chapter.

(c) The industrial, scientific, and medical equipment described in part 18 of this chapter.

(d) Any part or component thereof which in use emits radiofrequency energy by radiation, conduction, or other means.

[35 FR 7898, May 22, 1970, as amended at 54 FR 17711, Apr. 25, 1989]

§ 2.803 Marketing of radio frequency devices prior to equipment authorization.

(a) Except as provided elsewhere in this section, no person shall sell or lease, or offer for sale or lease (including advertising for sale or lease), or import, ship, or distribute for the purpose of selling or leasing or offering for sale or lease, any radio frequency device unless:

(1) In the case of a device subject to certification, such device has been authorized by the Commission in accordance with the rules in this chapter and is properly identified and labelled as required by § 2.925 and other relevant sections in this chapter; or

(2) In the case of a device that is not required to have a grant of equipment authorization issued by the Commission, but which must comply with the specified technical standards prior to use, such device also complies with all applicable administrative (including verification of the equipment or authorization under a Declaration of Conformity, where required), technical, labelling and identification requirements specified in this chapter.

...

(d) Notwithstanding the provisions of paragraph (a) of this section, the offer for sale solely to business, commercial, industrial, scientific or medical users (but not an offer for sale to other parties or to end users located in a residential environment) of a radio frequency device that is in the conceptual, developmental, design or pre-production stage is permitted prior to equipment authorization or, for devices not subject to the equipment authorization requirements, prior to a determination of compliance with the applicable technical requirements provided that the prospective buyer is advised in writing at the time of the offer for sale that the equipment is subject to the FCC rules and that the equipment will comply with the appropriate rules before delivery to the buyer or to centers of distribution. If a product is marketed in compliance with the provisions of this paragraph, the product does not need to be labelled with the statement in paragraph (c) of this section. 





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    Editor's note:

    The following section, Section 15.3, defines a couple of relevant 
    terms, notably, what comprises a digital device and furthermore 
    distinguishes between "Class A"  and "Class B" digital devices. 

    Make no mistake about it - 

      - Class A classified devices are meant for use in commercial, 
        industrial or business environments

      - Class B classified devices are meant for use in a residential 
        environments.

    Note: this *only* addresses 'digital devices', everything else, and 
    presumably (at least to my way of thinking) battery chargers, fence 
    chargers or anything else that doesn't use digital logic/microprocessors 
    to perform data processing as it's primary function (see para. k below) 
    *is not* - repeat after me - is not a digital device.

    Somehow, these new switchmode battery chargers have been able to be 
    classified as 'digital devices' and therefore greatly exceed normal 
    EMI/RFI limits imposed on non-digital devices ...

    Note below the use of the words "exclusive of" in paragraph h below - this 
    short phrase indicates that "Class A digital devices" are *not* considered
    to be a subset or include "Class B digital devices" as a category of devices.

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Part 15

Section 15.3 Definitions.

(h) Class A digital device.

A digital device that is marketed for use in a commercial, industrial or business environment, exclusive of a device which is marketed for use by the general public or is intended to be used in the home.

(i) Class B digital device.

A digital device that is marketed for use in a residential environment notwithstanding use in commercial, business and industrial environments.

Examples of such devices include, but are not limited to,

Note: The responsible party may also qualify a device intended to be marketed in a commercial, business or industrial environment as a Class B device, and in fact is encouraged to do so, provided the device complies with the technical specifications for a Class B digital device.

In the event that a particular type of device has been found to repeatedly cause harmful interference to radio communications, the Commission may classify such a digital device as a Class B digital device, regardless of its intended use.

... 

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    Editor's note:

    Here is the definition which I think is being misued by manufacturers of 
    switchmode power supplies/battery chargers.

    This definition of a 'digital device' looks pretty clear-cut to me; it is
    not intended, IMO, to include (or define) anything but data processing 
    equipment.  

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(k) Digital device.
(Previously defined as a computing device).

An unintentional radiator (device or system) that generates and uses timing signals or pulses at a rate in excess of 9,000 pulses (cycles) per second and uses digital techniques;

inclusive of telephone equipment that uses digital techniques or any device or system that generates and uses radio frequency energy for the purpose of performing data processing functions, such as

A radio frequency device that is specifically subject to an emanation requirement in any other FCC Rule Part or an intentional radiator subject to Subpart C of this Part that contains a digital device is not subject to the standards for digital devices, provided the digital device is used only to enable operation of the radio frequency device and the digital device does not control additional functions or capabilities.

Note: Computer terminals and peripherals that are intended to be connected to a computer are digital devices. 





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    Editor's note:


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Section 15.31 Measurement standards.

[As of December 2003]

(a) The following measurement procedures are used by the Commission to determine compliance with the technical requirements in this part. Except where noted, copies of these procedures are available from the Commission’s current duplicating contractor whose name and address are available from the Commission’s Consumer and Governmental Affairs Bureau at 1-888-CALL FCC (1-888-225-5322).

...

(3) Other intentional and unintentional radiators are to be measured for compliance using the following procedure excluding sections 4.1, 5.2, 5.7, 9 and 14: ANSI C63.4–2001: "Methods of Measurement of Radio-Noise Emissions from Low-Voltage Electrical and Electronic Equipment in the Range of 9 kHz to 40 GHz" (incorporated by reference, see § 15.38). This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.

NOTE to Paragraph (a)(3): Digital devices tested to show compliance with the provisions of §§ 15.107(e) and 15.109(g) must be tested following the ANSI C63.4 procedure described in paragraph (a)(3) of this section.

[As of July 2003]

(a) The following measurement procedures are used by the Commission to determine compliance with the technical requirements in this part. Except where noted, copies of these procedures are available from the Commission’s current duplicating contractor whose name and address are available from the Commission’s Consumer and Governmental Affairs Bureau at 1-888-CALL FCC (1-888-225-5322).

...

(3) Other intentional and unintentional radiators are to be measured for compliance using the following procedure excluding section 4.1.5.2, section 5.7, section 9 and section 14: American National Standards Institute (ANSI) C63.4–2001, entitled ‘‘American National Standard for Methods of Measurement of Radio-Noise Emissions from Low-Voltage Electrical and Electronic Equipment in the Range of 9 kHz to 40 GHz’’ published by the Institute of Electrical and Electronics Engineers, Inc. on June 22, 2001 as document number SH94908. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.

(i) Copies of ANSI C63.17-1998 and C63.4-2001 may be obtained from: IEEE Standards Department, 455 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855–1331, telephone 1–800– 678–4333 or +1-732-981-0600 (outside the United States and Canada).

(ii) Copies of ANSI C63.17-1998 and C63.4-2001 may be inspected at the following locations:

(1) Federal Communications Commission, 445 12th Street, S.W., Office of Engineering and Technology (room 7-B144), Washington, DC 20554,

(2) Federal Communications Commission Laboratory, 7435 Oakland Mills Road, Columbia, MD 21046, or

(3) Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. 





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    Editor's note:

    Here is the section where the manufacturers of switchmode battery chargers
    reap the benefit of misdefining their product as a 'digital device' -

    - note that the limits in paragraph (a) (for a "non-digital device") 
    are a LOT lower than the limits in paragraph (b) (the limits for a 'digital 
    device').

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Section 15.107 Conducted limits.

(a) Except for Class A digital devices, for equipment that is designed to be connected to the public utility (AC) power line, the radio frequency voltage that is conducted back onto the AC power line on any frequency or frequencies within the band 150 kHz to 30 MHz shall not exceed the limits in the following table, as measured using a 50 µH/50 ohms Line Impedance Stabilization Network (LISN). Compliance with the provisions of this paragraph shall be based on the measurement of the radio frequency voltage between each power line and ground at the power terminal. The lower limit applies at the band edges. 


 Frequency of           ---- Conducted Limit ------
 Emission (MHz)        QPeak                Average    
 -------------  -------------------    -------------------
 0.15-0.5       66 dBuV to 56 dBuV*     56 dBuV to 46 dBuV* 
               (2000 uV  to 631 uV*)    (631 uV  to 200 uV*)
 -------------  -------------------    -------------------
  0.5-5         56 dBuV  (631 uV)        46 dBuV  (200 uV)
 -------------  -------------------    -------------------
   5-30         60 dBuV  (1000 uV)       50 dBuV  (316 uV)
 -------------  -------------------    -------------------
     * Decreases with the logarithm of the frequency.
(b) For a Class A digital device that is designed to be connected to the public utility (AC) power line, the radio frequency voltage that is conducted back onto the AC power line on any frequency or frequencies within the band 150 kHz to 30 MHz shall not exceed the limits in the following table , as measured using a 50 µH/50 ohms LISN. Compliance with the provisions of this paragraph shall be based on the measurement of the radio frequency voltage between each power line and ground at the power terminal. The lower limit applies at the boundary between the frequency ranges. 
              
 Frequency of          ---- Conducted Limit ----
 Emission (MHz)        QPeak                Average    
 --------------  ------------------    ------------------
 0.15-0.5        79 dBuV  (8912 uV)    66 dBuV  (2000 uV)
 --------------  ------------------    ------------------
  0.5-30         73 dBuV  (4466 uV)    60 dBuV  (1000 uV)
 --------------  ------------------    ------------------








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    Editor's note:

    This Section applies to intentional radiators and spells out in different 
    language (from previous sections in Part 15) various radiated field
    strength limits.

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Radiated Emission Limits, Additional Provisions

Section 15.215 Additional provisions to the general radiated emission limitations.

(a) The regulations in Sections 15.217-15.255 provide alternatives to the general radiated emission limits for intentional radiators operating in specified frequency bands. Unless otherwise stated, there are no restrictions as to the types of operation permitted under these sections.

(b) In most cases, unwanted emissions outside of the frequency bands shown in these alternative provisions must be attenuated to the emission limits shown in Section 15.209. In no case shall the level of the unwanted emissions from an intentional radiator operating under these additional provisions exceed the field strength of the fundamental emission.

(c) Intentional radiators operating under the alternative provisions to the general emission limits, as contained in Sections 15.217 through 15.255 and in Subpart E of this part, must be designed to ensure that the 20 dB bandwidth of the emission is contained within the frequency band designated in the rule section under which the equipment is operated. The requirement to contain the 20 dB bandwidth of the emission within the specified frequency band includes the effects from frequency sweeping, frequency hopping and other modulation techniques that may be employed as well as the frequency stability of the transmitter over expected variations in temperature and supply voltage. If a frequency stability is not specified in the regulations, it is recommended that the fundamental emission be kept within at least the central 80% of the permitted band in order to minimize the possibility of out-of-band operation. 

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    Editor's note:

    I believe that some of the emanations from these switchmode battery chargers 
    categorized as "Class A digital devices" could be within the range of the 
    limits for intentional radiators ... the following paragraph details the 
    limits for the field strength of an intentional radiator in the 1.705 MHz 
    to 10 MHz range.
 
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Section 15.223 Operation in the band 1.705 - 10 MHz.

(a) The field strength of any emission within the band 1.705-10.0 MHz shall not exceed 100 microvolts/meter at a distance of 30 meters.

However, if the bandwidth of the emission is less than 10% of the center frequency, the field strength shall not exceed 15 microvolts/meter or (the bandwidth of the device in kHz) divided by (the center frequency of the device in MHz) microvolts/meter at a distance of 30 meters, whichever is the higher level. For the purposes of this Section, bandwidth is determined at the points 6 dB down from the modulated carrier. The emission limits in this paragraph are based on measurement instrumentation employing an average detector. The provisions in Section 15.35(b) for limiting peak emissions apply.

(b) The field strength of emissions outside of the band 1.705-10.0 MHz shall not exceed the general radiated emission limits in Section 15.209.