The invention provides a power line inspection apparatus comprising a vehicle body to which is mounted a power line traversal means, a power line inspection means to draw power from a power line to which it is attached, in use. A drain comprised of a first semiconductor material having a first band gap and a source comprised of a second semiconductor material having a second band gap are formed. According to this architecture, mass data can be transmitted effectively using the second forward satellite channel having a larger capacity than that of the first forward satellite channel. Other techniques may be utilized in which transmit power control is based on multiple interference estimates in a frame slot.