[R-390] Re chirping CW and low audio plus strange PTO problem.

[Forrest Myers]

Well, today I took the PTO apart. Inside it looked like a new one. All the
lubricant was still very moist and the spring on the stack follower was nice
and strong. I figured out the problem but didn't fix it. It appears that the
PTO was defective when manufactured and when it was linearized, it was done
only while tuning uphill.

The correction stack has a very sharp bend right around the 100khz point. I
checked both rollers as they passed the sharp bend and they both followed
just fine. Looking closer, I noticed that there was a slight gap between the
wafers in the stack. Looking even closer, I noticed that, when tuning
uphill, there was so much pressure on the wafer at the peak of the bend that
the wafer actually bent under the load and straightened out after the roller
passed it. When tuning down hill, the wafer wasn't under much pressure at
all and didn't bend at all, thus the difference in the linearity between
tuning up and tuning down.

I didn't see any easy way to fix it so just put it all back together. One
nice thing is that the rig still works and the linearity didn't change,
whew! Guess I'll just live with it unless anyone on the list has a way to
fix the problem.

I suppose, I could change the wafers such that it tuned correctly going
downhill and then fill the gaps between the disks with epoxy or something so
that they wouldn't bend while tuning uphill. Sounds like a lot of tedious
work to me.

Forrest Myers
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