[R-390] R-390 and CV-157 timeframe

[Sheldon Daitch]

This brings us an interesting change in focus in the R-390
series and its relationship to the CV-157 convertors.

The CV-157 has an AFC circuit, so, if an R-390 and a
CV-157 are teamed together, the absolute frequency drift
of the PTO in the receiver wasn't that important as long as
the total system drift, to include transmitter frequency
change, receiver PTO change and even the minor change in
the CV-157 tuning system, as long as that drift did not
exceed the range of the mechanical AFC variable capacitor.

So, I suppose the question might be, what is the relationship
between the fielding of the R-390 and then the CV-157?

Don't misunderstand that I am trying to put down the
stability of the R-390 series and the PTOs in general, but
someone in systems design recognized a need for the AFC
circuit in the CV-157.  Was the AFC added because of the
higher frequency stability requirements of multiple channel
RTTY circuits on a VF channel, due to even minor drift by
the PTOs or the frequency stability requirements even exceeded
the good specs on the R-390s?

73
Sheldon
WA4MZZ


>
> Another thought about T comp needs is that it's my understanding that 
> many of these receivers were used for RTTY and temp performance may 
> have been driven totally by those requirements.  Basic PTO temp 
> performance AND the oven may have been needed for long term "set and 
> forget" tuning stability.
>
>