Sec. 101.117  Antenna polarization.

    Except as set forth herein, stations operating in the radio services 
included in this part are not limited as to the type of polarization of 
the radiated signal, provided, however, that in the event interference 
in excess of permissible levels is caused to the operation of other 
stations the Commission may, after notice and opportunity for hearing, 
order the licensee to change the polarization of the radiated signal. No 
change in polarization may be made without prior authorization from the 
Commission. Unless otherwise allowed, only linear polarization 
(horizontal or vertical) shall be used.