Meaning
Regulatory modifications are defined by the Federal Communications Commission to govern software-enabled alterations in software-defined radio systems. A class 4 permissive change applies when a software update enables a new frequency band or changes the modulation type without any physical hardware modifications. This classification ceases to apply if the output power or maximum RF exposure of the system is increased beyond the original limits.
Software Modification
Digital changes to a transmitter allow manufacturers to update deployed devices with new capabilities through simple firmware downloads. When submitting a class 4 permissive change, the grantee must demonstrate that the software does not allow the user to adjust the radio parameters beyond certified limits. This procedure ensures that unauthorized software cannot be installed to bypass regional frequency allocations.
The approval is tied to the security architecture of the software-defined radio.
Spectral Profile
Test reports must be generated to confirm that the new software does not increase the out-of-band emissions. These tests focus on the spectral density and the unwanted emissions across the newly enabled bands.
Compliance Boundary
Software modifications that alter the fundamental frequency band are forbidden under this filing if they occur on non-SDR hardware. In those circumstances, a new equipment authorization is mandatory.
