In 1946 a SECRET Radar Pamphlet was handed out to all executive officers at the end of WW2. By just reading these three files, you will have an excellent overview of the origins of radar in the Royal Navy from 1938 until 1946. Have a good look at Page 34 in Part 2. The top picture shows the aerial for the very first Naval radar at sea in HMS Rodney and HMS Sheffield in 1938, which was Airguard Type 79. Now for a treat! This picture is of HMS Rodney with her radar aerials on both the foremast and the mainmast taken at a time when her crew are swarming over her with their tools, chipping-hammers and paint brushes. Note the man actual sitting on the foremast radar aerial. This is fortuitous and gives us a good idea of the size of the aerial as compared with the size of a man, albeit one bent over in a working position.

HMS RODNEY with her Type 79 Aerials
1946 RADAR pamphlet Part 1
1946 RADAR pamphlet Part 2
1946 RADAR pamphlet Part 3