Jack, I asked the same question here about 20 years ago. Robert/WA5CAB responded with the answer. I recall that there was a change issued to the RT-70A/GRC manual that detailed a few altered values of several capacitors and perhaps some resistors...very minor differences. I can not immediately locate the hard copy I received from Robert, but he is (of course) THE font of detailed knowledge for this. My RT-70B was made in 1958, and thus seems to be the last significant addition to the AN/GRC-3 series of radio sets before introduction of the AN/VRC-12 series a couple of years later.
I have one RT-70B/GRC installed in my AN/GRC-7 and one RT-70A/GRC installed in my AN/VRC-7. I don't know why, but this series of radio sets have fascinated me since I saw my first RT-68/GRC back in 1968.
Mike / KK5F
Anyone have the manual for the RT-70-B? Specifically the
B version. I have the manual for the basic unit and the -A
model.
Just would like to know what the differences between the
-B and the earlier versions are.
I have an RT-70-A, which works fine, and an RT-70(no suffix)
which looks like it was modified to the -A version, but the
the modified area doesn't quite match the schematic for the -A.
The radio in question came to me with half of the tubes with open
filaments, so I've been looking closely at things before committing
more tubes to the cause.
Thanks
Jack Antonio
WA7DIA