[R-390] Alignment question

[Jim Brannigan]

Thanks to all,

Glenn, I did find the schematic for the dummy load and Bob, the radio will
be used with a 50 ohm system so I put the URM-25 50 ohm load in line,
strapped the input connector and tuned it up.

Over all impression.
This R-390A was last aligned over 10 years ago.  It sees fairly light use.
Aligning the tuned circuits amounted to a "touch-up" as they were not far
off.  The biggest change was in the variable IF's and this was due to
restoring the 6C4 third mixer.
The most noticeable difference came from changing the audio coupling caps to
.033's, the audio sounds much better.

While it is on the bench I will run through the alignment again, then add
the CV-591 for a final test.
I am going to compare the CV-591 vs. an Eldico SBA-1 and see which one goes
back into the rack.

Jim


> In order to properly set up a R-390 for 50 ohm coax you need to strap the
> input of the radio or use a matching transformer. There are threads on
each
> back in the archives.
>
> Once the radio is more or less set up to run 50 ohms you then use a 50 ohm
> output impedance generator to align the radio. If you decide to set up for
> 75 ohms and use cable TV stuff then you need a 50 ohm to 75 ohm pad
between
> the generator and the radio.
>
> Chuck's good old R390 videos explain all this (except for Sputnik) a lot
> better than I can.
>
> Hope that makes at least some sense ...
>
>     Enjoy!
>
>         Bob Camp
>         KB8TQ