Would a car radar detector work?

I probably should know this answer but don't.

Car detector would not give direction or be as waterproof, but maybe
many times cheaper?

wrote:
Mine
is currently inactive as the crystals got fried by an overdose of
radiation, or so says the manufacturer.

You're not alone. A couple of friends have the same complaint about the
CARD. One unit was friend when he turned on his own radar.

I have a very old Combi unit (no longer made) which works great. But
AIS is so much better that I rarely turn the Combi on any more.

Jack