[R-390] DA-121 and R390/URR

[Barry Scott]

In the last few weeks, there were several posts regarding using the
DA-121 to determine sensitivity for, presumably, an R-390A/URR.  The
DA-121 uses a 68-ohm in parallel and a 100-ohm in series with the
signal generator's output.  Is this the recommended adapter also to be
used for the RF alignment of the R-390A/URR when using the balanced
input?

I ask because the R-390/URR manuals say to use a 75-ohm parallel
resistor with a 95-ohm series resistor when performing the RF
alignment.  I realize there's not enough difference between those two
networks to matter that much but I am curious as to why the two values
are different between the models.  Are the RF transformers slightly
different between them?

Just curious.

Thanks,
Barry - N4BUQ