[R-390] 390/390a alignment

[Dan Merz]

Hi,  I noticed the generator connection points for i.f. alignment of the
390a and 390 non-a differ.  The 390a puts the signal into the i.f.
chassis input whereas the 390 puts the signal into the grid of the 3rd
mixer.  I can imagine this is because the 390a mech filters offer a
degree of isolation not in the 390 but wonder if there is some other
reason.  Is the connector on a 390 non-a at the insertion point E210
(grid of 3rd mixer) the same type as E211 on the 390a,  or is it a BNC
connector?  All this wondering came up as I started going thru the i.f.
alignment descriptions  for the two radios,  and that for the R-725,  to
align the 390 non-a  chassis I put in the 390a radio.  thanks,  Dan.