[R-390] Question on COSMOS PTO

[DJED1 at aol.com]

What you're seeing sounds OK to me.  I always tune in one direction  when 
calibrating the PTO because I see some backlash on the order of what you've  
described. You have to remember that despite the 200 Hz markings on the readout  
the radio was spec'd to be accurate to only 300 Hz after calibration, and that  
was a marvel back in 1952!  
I've found the Cosmos to be affected by mechanical stress.  I  calibrated 
mine while mounted in the radio.  when I removed it and then  reinstalled it, I 
found a cyclical error of up to 1000 Hz (same error every 100  KHz).  I found 
that by retightening the mounting screws I could get back to  the original 
calibration of 300 Hz at all 25 Khz points.
I think your expecting too much from this old technology.  While it  was 
state of the art at the time, it can't compete with the new synthesized rigs  that 
will read out accurately to 10 Hz.
Of course, my experience is limited to one PTO, so others may have a  broader 
range of experiences.
Ed