Tex. Transp. Code § 504.415

The department shall issue specialty license plates for a person who holds an amateur radio station license issued by the Federal Communications Commission and who operates receiving and transmitting mobile amateur radio equipment. The license plates shall include the person's amateur call letters as assigned by the Federal Communications Commission. A person may register more than one vehicle equipped with mobile amateur radio equipment under this section, and the department shall issue license plates that include the same amateur call letters for each vehicle.