[R-390] PTO: Why does endpoint shift over time?

[ToddRoberts2001 at aol.com]

In a message dated 7/21/2007 8:08:55 AM Eastern Standard Time, 
tshoppa at wmata.com writes:
How come, after 30-40-50 years, haven't things
stabilized? I know for a lot of components there
is some drift after manufacture and bake-out during
use, but this period seems to be measured in
days and weeks, not big chunks of a century!
 
 
Tim
I "fixed" a couple of R-388 PTOs by removing one or two turns from the end 
point coils back in the 1980s. Since then the PTOs have remained dead-on, 
exactly ten-turns for a 1MHz change in frequency. So assuming the radios were built 
in the 1950s, in my cases the drift in the PTO end point seemed to stop after 
about 30 years from manufacture date.
73 Todd WD4NGG
 
 



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