After getting the quadcopter to fly in loiter and auto missions with confidence it was decided to use the quad copter for what it was originally intended for. To measure RF signal propagation. This measurement was done with a transmitter on one side of a 13m high man made berm and flying a vertical path up to 50m on the far side measuring the diffraction of the continuous wave signal at 400MHz. Below is a video with the payload strapped to the quadcopter, note that the antenna (yellow block) was exchanged for a small stub antenna at the actual measurement. The measurement was done using my RS232 spectrum analyser logging onto a Raspberry Pi. The effect of the quad copter on the antenna pattern was ignored and the measured data was treated as relative. The measured data can be seen below and clearly resembles a diffraction pattern. This pattern has been verified against some prediction code of a colleague. As a first test this proved very successful as a proof of concept and was hereafter named fEMu (flying Electromagnetic Metrology unit).