I used to work on the R390 back in the day in the navy.
That thing is a boat anchor! tubes and mechanically tuned slugs but the most sensitive reciever ever built. I could tweak on to have a minimum discrernable signal at -127dbm
This little Kaito is pretty neat. Selectivity isnt stellar but it fits in your pocket.
My Canadian friend calls them boat anchors, too-- I learned the "Bell Telphone Lineman's Trick" for setting gear like that in a relay rack- lay the danged rack down on its back, and drop the stuff straight down. Also used threaded rods ( studs ) with nuts instead of machine screws, so I didn't have to struggle to align the cuts in the front panels with screws and holes.
I tried to locate a link to that gear EdS on Free Dominion was talking about, but their "your posts" format is paged, and it was about two years ago- so I quit on page 38.
It was some sort of handheld transceiver that covered an amazing range of frequencies, voice, RTTY, SSB.
Just astounding how much technology was packed in to something smaller than an old bag telephone.
“I used to work on the R390 back in the day in the navy.”
I used to work with R390s back in the early 1980s. I don’t know but I might still be able to zero one out.