When an RF product is revised due to obsolete parts, cost cutting, or product improvements, how does the engineer know what the FCC requirements are for the altered product?  Will it require a new FCC filing and ID number or will a Permissive Change be allowed?

To allow products to be modified without requiring a new filing, the FCC has defined three Permissive Change options listed in Title 47 Part 2.1043, KDB 178919 D01 Permissive Change Policy v05r04.

Class I Permissive Change
This class includes modifications which do not degrade the characteristics accepted by the FCC when certification is granted. No filing with the Commission is required for a Class I Change.

Class II Permissive Change
This class includes modifications which degrade the performance characteristics as reported to the FCC at initial certification. In this case, the grantee must supply the Commission with results of tests of characteristics affected by the change.

Class III Permissive Change
This class includes software modifications of a software-defined radio transmitter that change the frequency range, modulation type or maximum output power (either radiated or conducted) outside the parameters previously approved.

In this case, the grantee must supply the FCC with a description of the changes and test results showing that the equipment complies with applicable rules with the new software loaded, including compliance with applicable RF exposure requirements.

Class III changes are permitted only for equipment on which no Class II changes have been made from the originally approved device.

For any of these changes, modified equipment cannot be marketed under the existing grant of certification prior to acknowledgment by the Commission that the change is acceptable.

In summary, changes to a modular radio or product will result in either a Permissive Change or a new FCC filing and ID number. The degree of change will determine both the process and the amount of supporting data required to illustrate compliance.

With few exceptions, a new FCC ID and a new equipment authorization application will be required in the event of changes to the basic frequency (including clock and data rates), frequency multiplication stages, basic modulator circuit, or maximum power or field strength ratings.