Pierce oscillator, from crystal to LC

[neazoi]

Hello a simple crystal pierce oscillator is shown here
**broken link removed**
Since the crystal is used as a feedback element, I was wondering if it can be replaced by an LC combination in order to make a vfo.
I have not seen any such circuits on the net.

 

[BradtheRad]

There is a family of oscillators which use LC resonance.
These are Colpitts, Clapp, Hartley.

The crystal is not replaced pin-for-pin with an inductor-capacitor pair, if that's what you're looking for. The types mentioned above arrange the LC differently, and have more than one inductor or capacitor.

 

[E-design]

This circuit will work with a wide combination of L and C.

 

[neazoi]

This circuit will work with a wide combination of L and C.

Is is a BJT pierce oscillator?

 

[E-design]

Yes, this was a design I did in another post. It can easily be altered for use with a JFET.

 

[neazoi]

Yes, this was a design I did in another post. It can easily be altered for use with a JFET.

Thank you! I will try it, probably the fet version.
Have you got any clue about it's stability and frequency coverage without any components alterations apart from the LC?

 

[E-design]

The short term stability will be affected by the loaded-Q of the LC combination. High LC ratios will have higher Q and better short term stability.

It can be seen in the plot below by keeping L constant and varying C the loaded-Q increase with higher frequencies.

If you want a VFO oscillator with more constant Q over the frequency range, then look at the Vackar topology.

https://en.wikipedia.org/wiki/Vackář_oscillator