47 CFR 95.425 - (CB Rule 25) May I make any changes to my CB station transmitter?
(a) You must not make or have any one else make any internal modification to your CB transmitter.
(b) Internal modification does not include:
(1) Repair or servicing of a CB station transmitter (see CB Rule 24, § 95.424); or
(2) Changing plug-in modules which were certificated as part of your CB transmitter.
(c) You must not operate a CB transmitter which has been modified by anyone in any way, including modification to operate on unauthorized frequencies or with illegal power. (See CB Rules 9 and 11, §§ 95.409 and 95.411.)