[Kenwood] TS 930 940 (maybe others) vfo 'speed up'

[Martin Sole]

Folks,

I'm curious. Can anyone provide a concise explanation of how the main
encoder 'speed up' circuitry works for either of the above two radios.
My TS 940 seems to tune very fast, that is to say the speed up function
seems to come into play very much sooner than the specified 2-3 rps. A
second TS940 here does not seem to do this and a TS930 that uses a
similar encoder but slightly different logic doesn't seem to speed up at
all, spec for the 930 is 5-6 rps for speed up to start.

I have been through the encoder set up, have driven the shaft at pretty
close to 300 rpm and unless the settings are mighty critical, all is
fine. It wouldn't be a problem except that my 940 seems to feel a little
rough to tune sometimes, more like it's jumping into 100Hz steps rather
than 10Hz steps.

I would love to understand how the speed up circuitry works.

Anybody care to write a nice logical(sic) explanation?

73's
Martin
HS0ZED