47 CFR 95.411 - (CB Rule 11) May I use power amplifiers?
(a) You may not attach the following items (power amplifiers) to your certificated CB transmitter in any way:
(1) External radio frequency (RF) power amplifiers (sometimes called linears or linear amplifiers); or
(2) Any other devices which, when used with a radio transmitter as a signal source, are capable of amplifying the signal.
(b) There are no exceptions to this rule and use of a power amplifier voids your authority to operate the station.
(c) The FCC will presume you have used a linear or other external RF power amplifier if -
(1) It is in your possession or on your premises; and
(2) There is other evidence that you have operated your CB station with more power than allowed by CB Rule 10, § 95.410.
(d) Paragraph (c) of this section does not apply if you hold a license in another radio service which allows you to operate an external RF power amplifier.