At some frequencies...
Robert;
I read the same thing about 20 years ago, in a NASA paperback on the state of SETI at the time (which I bought at a used book sale somewhere, so the data may have been older still), and have mentioned it here one or twice. No longer have access to the book, but as I recall, the phenomenon was specific to the wavelengths we use as radar, and resulted from NORAD and the Soviet counterpart. No idea if the condition still applies...
E'