When can I expect radar in destroyers?
 

I was wondering when I can start to expect destroyers / escorts will start to have radar?

I'm playing GWX 3.0, and in my last patrol I had an excellent night attack with a convoy where I attacked and re-attacked on the surface, sneaking up on the escort on the right flank to within about 1500m, sinking it and three merchant vessels.

I steamed away, plotted where I expected the convoy to be, and re-attacked and sunk another few merchants.

This is in March 1941, so it looks like they don't have radar sets yet. When should I expect radar to be introduced as a matter of course?

And also, is it different by class? Would a larger or more modern escort carry radar compared to, say, a Flower class escort?

You'll be running afoul of them soon.
http://www.navweaps.com/Weapons/WNBR_Radar.htm

Welcome aboard, Cheeky :salute::salute::salute:
Them Tommies is already watching :D