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is it possible to make XVCO from LC VCO ?

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Alex_IC

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butler vco

Hi!

Is it possible to make a XVCO from LC VCO like in fig.1? To get XVCO I'm going to replace the L by crystal.

Thank you!

 

vfone

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Re: XVCO from LC VCO

Maybe you want to say VCXO.
XVCO doesn’t exist yet in electronics terminology.
Just replacing an L with a crystal is not enough to get a good Variable Crystal Oscillator.
Now depends by the frequency of the crystal, by the crystal cut, and not to the last by the oscillator type. From what I know, with Butler VCXO oscillator you get the most ppm variation of the frequency.
 

Alex_IC

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Re: XVCO from LC VCO

Thanks for reply,

Let say I need +/-100 ppm variation of the frequency and the freq=400 MHz. Can I use the above circuit just replacing L by crystal ? Does temp stability degrade in this circuit dramaticcaly?
 

vfone

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Re: XVCO from LC VCO

Hard to tell you just from a basic oscillator schematic.
If you have all the transistor models run a simulation, replace the L with a crystal and see what variation in ppm you get.
Generally parallel tank configurations get lower ppm variation than series tank X-tal oscillator.
 

riziahm

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XVCO from LC VCO

How can a crystal which is designed, for example, mechanicle vibration at 25MHz would resonate at 400MHz?

Are you saying the crystal is at 400MHz?
 

Alex_IC

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Re: XVCO from LC VCO

To riziahm

It could be a SAW resonator. The operation is the same.
 

neazoi

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Re: XVCO from LC VCO

Alex_IC said:
To riziahm

It could be a SAW resonator. The operation is the same.
No it is not exactly the same, and note that the L-C can handle much power but the crystal can handle only very low powers. SOme radio amateurs use more than one identical crystals in parallel.
 

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