[time-nuts] Methods for comparing oscillators

[Bruce Griffiths]

Tom

The specified mechanical adjustment range for the 10811A is greater than
(-10Hz, +10Hz) so in principle one should be able to achieve an offset
of up to 10Hz or so.
I'd try doing this first, then of the 2 methods suggested changing the
crystal load capacitance if its feasible to do so would be the preferred
option as the oscillator stability will be less impaired than if the
oven temperature were varied, at worst only a relatively small change in
capacitance will be required.
If the motional parameters of the crystal were known then the required
capacitance change can be estimated before dissassembly.

Looking at the oscillator circuit the 1-30pF mechanical trimmer cap is
connected in parallel with a 100pF varicap which is in series with 16pF
so adjusting the frequency down if the trimmer is at its lowest
capacitance will be difficult, adjusting the frequency up by connecting
a small cap high quality across the trimmer should be easy to do.

Bruce

Tom Van Baak wrote:
>> A 1Hz offset may be convenient as its easy to adjust an 10811A or
>> similar to achieve this.
>> A 10Hz offset is harder to achieve.
>
> Would either of these be 10 Hz solutions?
> 1) open the 10811 and change the xtal load capacitance, or
> 2) change the oven temperature set point until the resonator
> is 10 Hz off. You'd loose a little in tempco but...
>
> /tvb