[R-390] IF Alignment in the R390/URR

[Barry Scott]

The IF alignment instructions for the R390/URR (and, and I recall, the
R390A/URR as well ) begin by adjusting the signal generator to the
frequency that provides the highest voltage on the DIODE LOAD.
Apparently, this is not always 455.000kc but I'm not sure I follow why
it isn't.

When I read this, I made a possibly false assumption that having a
signal generator with a precision readout or an accurate counter
wasn't usually available and adjusting for the "best" frequency was
the best approach.  When I aligned mine, I chose to use 455.000kc but
now I'm wondering if that was a mistake.  The primary reason I did
that was so that the BFO could be a zero-beat when it was also at
455.000kc.  That may really be irrelevant but it was my reason.

I started looking at the STAGE GAIN procedures and when I injected the
signal into the 6th IF amp's grid, I could tell that 455.000kc wasn't
getting me the peak on the DIODE LOAD and, instead tha frequency is a
few kc away from there so something isn't right about my setup;
however, I'm still puzzled at why the IF chain can't be "forced" to be
peaked right on 455kc.  Is this because there are some fixed values in
the transformers and a "best" frequency is the best one can do with
those fixed values? If not, then would someone please explain this to
me as I'm still not making sense of it.

Thanks,
Barry - N4BUQ