On May 22, 8:32 pm, Jim Mandaville wrote:
I am working over a Navy RBM receiver (the HF version) that I got at a
swap meet some years ago. It has zero value as a collector's item as
some previous owner (perhaps even the U.S. Gov.) was nice enough to
remove all the nameplates except the list of patents! I have the manual
for the "RBM, RBM1, RBM2 and RBM3" and this has all the necessary
diagrams, part lists and alignment info. It does not, however, give any
indication of how the different versions (1, 2, 3 and higher) differed.
Can anyone give me a brief overview on this question? My version, if
this is worth anything, has the big letters on the dials ("T" for tune,
"B" for band, etc. I'm trying to figure out what version this is ....

Seems from what I can find, the -4 RBM was the .2-2.0mcs version & the
-5 was the 2.0-20mcs version.
I have the -5 with those large engraved letters on the knobs.
Thankfully I also have the AC power supply es cable.
Someday I gotta bring it up on a Variac es see how she plays:-)