Radiophysics theory usually gives a pretty good prediction of what the shape will be, and communications engineers use it to design ground antennas well matched to satellite beam shapes. Photo Wayne Deeker. But sometimes the antennas don t perform exactly as predicted. Also there may be error causing limitations with the theoretical models. In the worst case, this interference can create radio dead spots, where the satellite cannot communicate with Earth from certain angles.
Testing involves simulating two-way communications with the satellite in a special chamber.
The test information can confirm that everything s okay, or can suggest ways to redesign the antennas to improve reception. Dr Hay explains the test aims. We are trying to satisfy the requirements of FedSat in qualifying the antennas. About 5 metres from the pedestal, at one end of the chamber, is the radio transmitter. Then the antenna under test is rotated about its axis, and the measurement is done again, and that gives you cuts through the radiation pattern as you turn.