[time-nuts] injection locking crystal oscillator

[Bob kb8tq]

Hi

How close to frequency is the 10 MHz oscillator?

Is the crystal a fundamental? 

The degree you can injection lock an oscillator is (as Danna notes) a bit difficult 
to predict. Your chances improve if the oscillator is low(er) Q. They also improve
if it is tuned very close to frequency. Past that it’s a function of power. 

Also keep in mind that when the GPSDO drops out, you likely will get a “burp” 
in the output of the injection locked oscillator. That may unlock your PLL. 

It sounds like the oscillator i this case is not tuned in a normal sense ( = there is 
nothing to adjust it dead on frequency). First step probably would be to add that
“feature” to the circuit. 

Bob

> On Feb 28, 2019, at 6:43 PM, Thomas S. Knutsen <la3pna at gmail.com> wrote:
> 
> Hello.
> 
> I have a device that consists of a PLL, that has as its reference a
> 10MHz crystal.
> What I would like to do, is to inject this with 10MHz from a GPSDO,
> when that is available, and to use the internal crystal when that is
> not available.
> 
> Would it be feasible to just connect it to one leg of the crystal
> oscillator with a small capacitor, and with that get injection
> locking?
> The crystal oscillator is on chip, there is a couple capacitors that
> allow for frequecy adjustments, other than that, I know nothing about
> what is on the chip. The PLL is SP5769.
> 
> Br.
> 
> Thomas
> 
> -- 
> With Best regards, Thomas S. Knutsen.
> 
> Please  avoid sending  me  Word  or  PowerPoint  attachments.
> 
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