Recommendation itu-r sm. 1538-1 Technical and operating parameters and spectrum requirements for short range radiocommunication devices




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9.2 What changes can be made to an FCC-authorized device without requiring a new FCC authorization?


The person or company that obtained FCC authorization for a Part 15 transmitter is permitted to make the following types of changes:

For certified equipment, the holder of the grant of certification, or the holder’s agent, can make minor modifications to the circuitry, appearance or other design aspects of the transmitter. Minor modifications are divided into two categories: Class I permissive changes and Class II permissive changes. Major changes are not permitted.

Minor changes that do not increase the radio frequency emissions from the transmitter do not require the grantee to file any information with the FCC. These are called Class I permissive changes.

NOTE 1 – If a Class I permissive change results in a product that looks different to the one that was certified it is strongly suggested that photos of the modified transmitter be filed with the FCC.

Minor changes that increase the radio frequency emissions from the transmitter require the grantee to file complete information about the change along with results of tests showing that the equipment continues to comply with FCC technical standards. In this case, the modified equipment may not be marketed under the existing grant of certification prior to acknowledgement by the Commission that the change is acceptable. These are called Class II permissive changes.

Major changes require that a new grant be obtained by submitting a new application with complete test results. Some examples of major changes include: changes to the basic frequency determining and stabilising circuitry; changes to the frequency multiplication stages or basic modulator circuit; and, major changes to the size, shape or shielding properties of the case.

No changes are permitted to certified equipment by anyone other than the grantee or the grantee’s designated agent; except, however, that changes to the FCC ID without any other changes to the equipment may be performed by anyone by filing an abbreviated application.

For verified equipment, any changes may be made to the circuitry, appearance or other design aspects of the device as long as the manufacturer (importer, if the equipment is imported) has on file updated circuit drawings and test data showing that the equipment continues to comply with the FCC rules.


9.3 What is the relationship between V/m and W?


Watts (W) are the units used to describe the amount of power generated by a transmitter. Microvolts per metre, V/m, are the units used to describe the strength of an electric field created by the operation of a transmitter.

A particular transmitter that generates a constant level of power, W, can produce electric fields of different strengths, µV/m, depending on, among other things, the type of transmission line and antenna connected to it. Because it is the electric field that causes interference to authorized radiocommunications, and since a particular electric field strength does not directly correspond to a particular level of transmitter power, most of the Part 15 emission limits are specified in field strength.

Although the precise relationship between power and field strength can depend on a number of additional factors, a commonly-used equation to approximate their relationship is:

where:

P : transmitter power (W)

G : numerical gain of the transmitting antenna relative to an isotropic source

D : distance of the measuring point from the electrical centre of the antenna (m)

E : field strength (V/m)

4 π D2 : surface area of the sphere centred at the radiating source whose surface is D m from the radiating source

120 π : characteristic impedance of free space ().

Using this equation, and assuming a unity gain antenna, G  1 and a measurement distance of 3 m, D  3, a formula for determining power (given field strength) can be developed:



P  0.3 E2

where:


P : transmitter power (e.i.r.p.) (W)

E : field strength (V/m).

The actual version of Part 15 of the FCC Regulation 47 CFR Ch. may be downloaded free of charge from the website of the FCC: http://www.fcc.gov/.



Appendix 3
to Annex 2

(People’s Republic of China)



Technical and operating parameters requirements and spectrum requirements for SRDs used in China at present

1 Technical parameters requirements

1.1 Cordless telephone


Transmit frequencies used for base set (MHz): 45.000, 45.025, 45.050, ..., 45.475

Transmit frequencies used for hand set (MHz): 48.000, 48.025, 48.050, ..., 48.475

Total channel number: 20

Maximum transmit power: 20 mW

Maximum occupied bandwidth: 16 kHz

Frequency tolerance: 1.8 kHz

Maximum adjacent channel power: 0.5 mW

Maximum spurious emission power: 25 W


1.2 Wireless audio transmitters


– Operating frequency band: 88 to 108 MHz

Maximum transmit power: 3 mW

Minimum spurious emission power attenuation: 30 dB

– Operating frequency band: 75.4 to 76 MHz

Maximum transmit power: 10 mW

Minimum spurious emission power attenuation: 30 dB

– Operating frequency band: 84 to 87 MHz

Maximum transmit power: 10 mW

Minimum spurious emission power attenuation: 40 dB

– Operating frequency bands: 470 to 510 MHz, 702 to 798 MHz

Maximum transmit power: 50 mW

Minimum spurious emission power attenuation: 30 dB

Modulation type: F3E

Maximum occupied bandwidth: 200 kHz;

Frequency tolerance: 100  10–6

1.3 Radio transmitters used for control of models


Operating frequencies (MHz): 26.975, 26.995, 27.015, 27.045, 27.065, 27.095, 27.115, 27.145, 27.195, 27.225

Maximum transmit power: 1 W

Maximum occupied bandwidth: 8 kHz

Frequency tolerance: 20  10–6

Minimum spurious emission power attenuation: 45 dB

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