When does radar hit the scene?

[bstanko6]

I am playing mid July 1940 and I notice I am being attacked by ships but they are not in visual range. I just want to verify radar use, and not a glitch in the game!

[Plumber1]

Historically speaking the allies didn't start using primitive surface radar until spring '41; not sure if this is accurately modelled in the game though.

Steve.

[bstanko6]

is it possible that it is huff/duff?? I don't know if it is in the game.