I owned a R390. Sadly I sold it. Big, clunky, but an amazing receiver.
Mechanical tuning mechanism was unique.
The PTO on the S-line is also unique. Slug tuned, a real challenge to tweak. Had to buy at Bristol (splined) allen wrench to accomplish some fine tuning. Mine has the best mechanical CW filter. Wonderful quiet receiver. Not that sensitive on higher frequencies, but can really handle front end overload.
Yeah the darn thing was a mechanical and electrical marvel.
I would listen to baseball on that in places I cant tell you about on a AN/BRD-7.
I got the R390 Collins and the AN/BRD-7 Sanders and Associates mixed up in a muddle of nostalgia. LoL