[time-nuts] FTS 1200

[bg at lysator.liu.se]

Bert,

Good that you got the EFC working!   But I would be a bit suspicious of
needing -13V.

It seems from:
  http://www.ece.gatech.edu/academic/courses/ece4007/08fall/ece4007l01/al4/datasheets/symmetricon_oscillator_instructionsheet.pdf

that the default EFC configuration is (0 to +10)V with a range of 4e-7
(2Hz). From the same document there are a lot of other EFC configurations,
but none that goes outside of +-10V.

My 1200 has about 3.5Hz tuning range on (0,10)V. Se attached jpg. I did
not check behavior on negative EFC voltage.

--

   Björn

> John,
>  that did the trick I can tune it with a negative voltage, minus 13  gives
> me plus 2 Hz but this unit came out of a FTS 5000 and it had a positive
> tuning voltage.
> Bert
>
>
> In a message dated 8/9/2012 9:13:29 P.M. Eastern Daylight Time,
> jmiles at pop.net writes:
>
>>  John
>> Oven did reduce in current and I can not imagine that it would be  that
>> close with an overheated oven. At 0 V it is within .5 Hz of what  they
> normally
>> are. Ground has no effect but even 0.8 V on pin 2  stops oscillation
>
> That's a suspicious-sounding voltage.  Are you  sure you're not
> forward-biasing the varicap?  Maybe some of these  OCXOs were specified
> for
> use with negative EFC voltage.
>
> If so, then  driving the diode with a negative voltage should raise the
> operating  frequency (which is what you want.)
>
> -- john,  KE5FX
> www.miles.io
>
>
>
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