I am being semi silly. I was only familiar with ATC radar. I don’t know what the capabilities of early warning radars are. I doubt if a Russian aircraft, that was trying to penetrate US airspace, would be squawking any code. I don’t even know what kind of IFF/SIF equipment Russian aircraft have, so I wouldn’t know if Russian Bears flying off the coast of Alaska are squawking anything, while out in international airspace. My job was to keep them apart, not run them together, as in running intercepts.
I read “Skunkworks” about Ben Rich who took over from Kelly Johnson, and he was the driving force behind the stealth fighter.
In 1975, we had radars that could see a BB from 5 miles away. (I thought it was 20 miles, but I might be getting it mixed up with the fact they could detect a soaring hawk from 20 miles away)
To have an independent authority test the claims made by Lockheed that they reduced the radar signature of a plane by 1000x (Northrop was claiming they fabricated their data to get government contracts) they had a guy from MIT come out to verify their claims.
His equipment was a container with ball bearings ranging from the size of a marble to the size of a BB.