[time-nuts] Typical EFC frequency response (bandwidth) of a OCXO

[Rick Karlquist]

Stephan Sandenbergh wrote:
>> charts, it is my guess that the loop bandwidth will be in the order of
> 1kHz.
> Thus, if I can't modulate the 100MHz OCXO at this rate, I will have to
> think
> of another plan.
>

First of all. realize that the modulation bandwidth of the VCO has
to be at least 10 times the loop bandwidth and preferrably a lot
more in order for it not to seriously decrease the loop damping factor.
Hence, 1 kHz loop bw is completely unrealistic for a crystal oscillator. 
The typical 3 dB resonator bandwidth of a crystal is only a few dozen
Hz.  This alone restricts the modulation bandwidth to a 10 Hz at best.

In particular, in the 10811, the ALC loop will react adversely to
fast modulation, and turns out to the be limiting factor.

If you want to clean up a crystal oscillator, you need to use a phase
modulator following the oscillator.

Rick Karlquist N6RK