 In testing the transmitter proved only barely suitable in the air @-@ to @-@ air role , with short detection ranges due to its relatively low power . But to everyone 's surprise , it was able to easily pick out the wharves and cranes at the Harwich docks a few miles south of Bawdsey . Shipping appeared as well , but the team was unable to test this very well as the Heyford was forbidden to fly over water . After this success , Bowen was granted two Avro Anson patrol aircraft , K6260 and <unk> , along with five pilots stationed at Martlesham to test this ship @-@ detection role . Early tests demonstrated a problem with noise from the ignition system interfering with the receiver , but this was soon resolved by fitters at the Royal Aircraft Establishment ( RAE ) . 
