I didn't really notice much backlash, though when setting oscillators I try to approach (slowly) from one direction until it's "good enough" and then stop, to avoid that problem.
On Dec 24, 2017, 11:28 AM, at 11:28 AM, Dana Whitlow <k8yumdoo...@gmail.com> wrote: >John, > >Do you notice a backlash effect when homing in on the desired setting >with >those >tripots? I last used such things back in the 1980's, and remember >often >having >enough backlash to make close trimming rather difficult. > >I wonder if they have gotten better in that regard. > >Dana > >On Sun, Dec 24, 2017 at 9:58 AM, John Ackermann N8UR <j...@febo.com> >wrote: > >> I'm glad that the PulsePuppy post spawned some good discussion! >> >> The pot I'm using is a Bournes 3296W-1-103LF which is a 25-turn, 10K, >> cermet pot, spec'd at 100ppm/degree, so it's not anything super >fancy. The >> number of turns provides decent setability, and it seems to be a good >match >> for the class of oscillator the PulsePuppy is designed for -- I found >that >> I could trim the Isotemp oscillator without problems. >> >> I'll admit up front that the PulsePuppy wasn't designed as a host for >> ultra-stable oscillators. I tried to keep the circuit board size and >cost >> down, as well as the number of components that users would have to >> install. And since the EFC trimmer is one of those user-installed >parts, >> it's possible to substitute as nice a pot as you'd like. I have one >unit >> that's hooked up to an external precision pot with a turn-counter >dial >> (just because it was there). >> >> John >> ---- >> >> On 12/24/2017 03:57 AM, Mark Goldberg wrote: >> >>> Can you specify what pot you have used? I am using some for my TCXO >boards >>> and am not quite happy with the settability or mechanical stability. >>> resulting in noise and higher Allan Deviation. >>> >>> A low noise regulator driving it also helped. >>> >>> I subscribe to the opinion to not use any extra resistors. When the >pot is >>> used as a voltage divider, theoretically it should have the same TC >>> throughout, so temperature effects should not affect the divide >ratio or >>> the output. Only the input impedance of the control voltage input to >the >>> oscillator relative to the effective resistance of the pot will >provide >>> some effect with temperature. >>> >>> Mark >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>> ailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.