It's not exactly uncommon, but I'd prefer the uncountable, "with (by means of) radar" or the countable "with a radar
device / gun." (in the second case, "radar" is an adjective.)
Radar as a thing ("a radar") is a bit low register.
Of course, "a TV set" was eventually replaced by "a TV." And in the very distant past, a radio was "a radio set."
It's just that radar is used in so many different ways.
But when you see a cop sitting on his bike pointing a unit (radar gun) at you, it's unlikely you'd say, "He was pointing a radar at me."
- A.