[R-390] Cosmos Drift

[Flowertime01 at wmconnect.com]

Jon,

I think Cecil hit it with the new tube idea.

However, as operators we never tried to keep a R390/A on a frequency for days.
A 1000 Hz drift over 3 days ain't all that much unless you are doing SSB.

All that care you gave that PTO may take some time to settle in.

Some of it may be your freq counter settling down. 
How often do you run it 3 days at a time?

Leave the receiver on and get some time on the tubes.
30 days 24 x 7 minimum. 

Then check the drift.

Roger AI4NI