my uncle was a radar operator in a radar equipped avro lancaster submarine hunter. im thinking this may have been the first example of AWACs aircraft. they would fly over the english chanel searching for german submarines and then alert the nearest destroyer. anyway these were extremely primitive versions of radar so i guess it was sending all kinds of different rays, maybe gamma rays or maybe even microwaves. he said that when ever he would turn on the radar the fillings in his teeth would get really hot.
You might like this site: The Wizard War: WW2 and the Origins of Radar. They have some information on early airborne radar and even some explanations of how some of it works.