47 C.F.R. § 95.425 (CB Rule 25) May I make any changes to my CB station transmitter?
Title 47 - Telecommunication
(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.) [48 FR 24894, June 3, 1983, as amended at 63 FR 36610, July 7, 1998]
Title 47: Telecommunication
PART 95—PERSONAL RADIO SERVICES
Subpart D—Citizens Band (CB) Radio Service
Other Things You Need To Know
§ 95.425 (CB Rule 25) May I make any changes to my CB station transmitter?

