Whether you hold any type of licence or not, you must still obtain a Certificate of Competency to operatre an Air/Ground radio station and this certificate must be signed as has been said before, by the radio station licence holder to signify that they have approved you to use their radio station.
An ATCO with current ADV or ADI ratings or a FISO may apply for this certificate and it will be issued free; all others (including FRTOL holders) must pass an exam with an authorised examiner.