Well, I cannot comment about the 509 PTO because I never laid hands on one.
But I have worked on plenty of other PTO tuned gear. Properly done, the cores
have very little contact with the coil forms, making PTO tuning among the
smoothest to tune I have seen. One in particular had a four coil PT setup
(preselector, RF amp grid, RF amp plate, Osc) with about a two pound flywheel
on the
tuning shaft. Start it spinning and it would travel from one end to the bump
stop on the other end of the dial without effort.
The bump stop was important because it used a dial cord on each end of the
core to '"pull-pull" the cores through the coils. Any binding would have
resulted in the cord coming off a pulley. Which would have been a disaster
because
those things were almost impossible to get to track when something happened to
the dial string.
On the other hand, the ganged rotors on some of the five gang air variable
capacitors used to tune some communications gear I had to maintain had up to
six
bearing points and even the slightest dust in a bearing made tuning rough.
Cleaning the tuning cap was a necessary and almost daily chore when half the
dirt in Wyoming was blowing in from the West.
73 Pete Allen AC5E
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