(a) increase the height of a structure supporting the radiating portion of the antenna; (b) relocate an antenna where such relocation would involve a change in the geographic co-ordinates of latitude or longitude by as much as one second, or relocation involves a change in street address; (c) change in antenna parameters, including height, number of antenna elements, radiation pattern or polarization. (6) All licensees shall, unless exempted by the terms of authorization, transmit the assigned call sign at the end of each complete transmission. (7) The transmission of the call sign at the end of each transmission shall not be required in cases of projects requiring continuous, frequent or extended use of the transmitting apparatus, if, during the periods and in connection with the use, the call sign is transmitted at least once every thirty minutes. 9. Sharing of frequencies. (1) The Commission may, where necessary, require a licensee to share a frequency. (2) The Commission shall implement the sharing through an arrangement that shall not impose unreasonable burden to the licensee involved. 10. Frequency spectrum pricing. (1) The Commission may from time to time prescribe the methods of determining frequency spectrum pricing. (2) The Commission shall not avail frequency spectrum licences to a licensee unless the licensee has paid frequency spectrum licence fees and complies with the conditions imposed by the Commission. (3) The Commission may recall frequencies assignments that have not been utilized within the period specified in the licence. (4) Where a frequency assignment is recalled for non-utilization, the licence fee paid in accordance with paragraph (2) shall not be refunded.