This event was set in May of 1940, I am not sure but I think that this was prior to the widespread usage of radar in WWII.
There seems to be many myths about radar and its use in WW2.
It was in use by all the "major" players on their entry into hostilities.
The technology was invented independently by each and then kept as a close held secret.
It basically grew out of research into television and death rays. A fertile combination!
Each country initially thought they were the only ones that had it, but a deal of cross-pollination took place amongst the Allies rapidly after the war started.
Different countries, and different arms therein, had different thoughts on how and where it should be used.
An example of the last would be at this time of the war the Germans had technically better radar than the British and the French, Dutch and Italians. Their installation of it was widespread enough, but its use as a potent air defence tool was less notably successful than the British. Hermann Diehl did develop a system of daylight fighter direction in 1939. It was put to use and is credited with the destruction of a raid of Wellingtons in the Battle of Heligoland Bight on 18 Dec 1939. It is easily arguable that the less sophisticated Chain Home and Chain Home Low installations were utilised far more effectively as an integrated part of Britain's air defence.
None of which, incidentally, has anything to say about radar use in FSO and it isn't intended to do so.
Louis Brown's "Technical and Military Imperatives, A RADAR history of World War II" is the shiznit for insights into this very interesting subject.
rgds