Guidelines for FCC Permissive Changes

By: Dave Neperud

Dave has been at LSR since 2001 and is the Senior RF Engineer. Dave has 21 years of experience in RF and wireless designs. Dave is a graduate of the University of Wisconsin–Madison (BSEE 1989) and of the National Technological University (MSEE 1997). He holds one patent.

FCC Certification: New Filing vs. Permissive Change

Products are continually under revision due to obsolete or unavailable parts, cost cutting, updates for a product release, and so on. The dilemma for most companies is determining the process and requirements for altered products. This article outlines the options available and highlights a few examples for guidance.

Read More about FCC testing and certification from LSR.

Here we focus on changes for unlicensed transmitters that require an FCC Certification or Equipment Authorization. Products require DoC testing if the change could adversely affect the radiating characteristics of the equipment. This procedure is outlined in Title 47 Part 2.1073.

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.

Class I Permissive Change

This class includes modifications which do not degrade the characteristics reported by the manufacturer and accepted by the Commission when certification is granted. No filing with the Commission is required for a Class I Permissive Change.[1]

Class II Permissive Change

This class includes modifications which degrade the performance characteristics as reported to the Commission at initial certification. Such degraded performance must still meet the minimum requirements of the applicable rules. When a Class II permissive change is made, the grantee must supply the Commission with complete information and results of tests of characteristics affected by such change. Modified equipment cannot be marketed under the existing grant of certification prior to acknowledgment by the Commission that the change is acceptable.[2]

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, or that change the circumstances under which the transmitter operates in accordance with Commission rules.

When a Class III Permissive Change is made, the grantee must supply the Commission 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. The modified software must not be loaded into the equipment, and the equipment must not be marketed with modified software under the existing grant of certification, prior to acknowledgment by the Commission that the change is acceptable.

Class III changes are permitted only for equipment on which no Class II changes have been made from the originally approved device.[3]

Following are examples of three common changes to certified radios.

Example 1: Change of Antenna for a Part 15 Subpart C Unlicensed Radio

Both products and modules are tested and certified with specific antennas. In many cases the end user deviates from the specified antenna due to cost, style or availability. To maintain a Class I Permissive Change, the new antenna must be an equivalent antenna, defined as one of the same type (e.g., yagi or dipole) and must be of equal or less gain than an antenna previously authorized under the same FCC ID, and must have similar in-band and out-of-band characteristics (consult specification sheet for cutoff frequencies).[4]

Therefore, if the antenna is of a different type or higher gain, the product or radio module requires a Class II Permissive Change, and all FCC provisions of Title 47 CFR 15.203 for antenna requirements must be met.

Example 2: Electrical Hardware Changes

The main deciding factor for hardware changes is whether the device is “electrically equivalent.” If the device is electrically equivalent, a Class I or Class II Permissive Change is acceptable, depending on the test result evaluation. Again, it is the manufacturer’s responsibility to ensure that the devices are electrically equivalent and to perform analysis that the device’s performance has not degraded. Some form of testing is generally required to support the claim that the device’s performance has not degraded.

Changes in frequency or output power, or removal or addition of components related to the RF section of the device automatically require a new filing and new FCC ID number.

Example 3: Enclosure Change

Obviously, enclosure changes do not apply to modular radios, but for other products, slight changes are allowed to the enclosure under a permissive change. However, major reorientation of the device inside the enclosure is not acceptable. For example, if the device was originally tested and certified lying flat and the new enclosure has the device mounted vertically, this would require retesting and a new FCC filing.


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 is the determining factor for both the process and the amount of supporting data required to illustrate compliance. LSR takes pride in helping customers evaluate and develop the most beneficial test plan to properly address these changes.

[1] 2009  Title 47 CFR 2.1043 ((b)(1))

[2] 2009  Title 47 CFR 2.1043 ((b)(2))

[3] 2009  Title 47 CFR 2.1043 ((b)(3))

[4]  178919 D01 Permissive Change Policy v04r04

Contact LSR for FCC testing services or consulting.