[time-nuts] Trimble 34310-T EFC Question

[John C. Westmoreland, P.E.]

Hello Bob,

If you think you are getting any high frequency into the EFC control - it
may be worth putting a(nother) low-pass filter in there.  Are you measuring
noise on that line?

Do you have a snap-shot of a schematic?  Or, can you take a picture of that
circuit?  I would hazard a guess you don't want to change the op-amp in
such a way the gain is too high - the circuit could be designed for unity
gain.  A different choice in resistors could still yield unity gain and
maybe knock down the noise a bit.

I would need to put an ammeter in the circuit to determine if there was any
meaningful current flow - without injecting noise of course... ;)

73's,
John
AJ6BC


On Wed, Nov 6, 2013 at 7:26 PM, Bob Stewart <bob at evoria.net> wrote:

> I think I may need to change the LPF feeding the EFC in my GPSDO to get
> rid of dithering jitter.  Is there any point in adding a resistor and cap
> in the EFC line, or do I need to go back and change the values in the
> op-amp circuit feeding it?  Currently an op-amp directly feeds the EFC
> pin.  I guess this boils down to something like: is there any meaningful
> current flow in EFC circuit in this oscillator?  Or should I add them but
> will I probably have to change the existing filter, as well?
>
> Bob - AE6RV
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