Question about crystal oscillator

beenthere

Joined Apr 20, 2004
15,819
Crystal oscillators tend to be single frequency devices, although they can be used at harmonic frequencies. Here is the Wikipedia article about them - http://en.wikipedia.org/wiki/Crystal_oscillator.

If you are careful about layout and bypassing, the oscillator would be reasonably stable. But it won't tune to a different frequency, although you can always drop in another crystal.
 

Thread Starter

gaetan8888

Joined Nov 14, 2008
50
Hello

In the web site it say that you can adjust the frequency by changing C1 value, so I would use a triming capacitor and replace it by a fix cap wen I would have the right frequency.

Thank

Bye

Gaetan
 

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SgtWookie

Joined Jul 17, 2007
22,220
Read it again!

Values of capacitor (C1) and xtal (X1) to be varied for required frequency.

The crystal sets the basic frequency.

It's possible with careful tuning to get the circuit to oscillate at various overtones of the crystal's fundamental frequency, but these are basically multiples of the fundimental.

If you want xtal stabilized clocking at various rates, you'll need to start out at a higher frequency and use clock dividers.
 

Thread Starter

gaetan8888

Joined Nov 14, 2008
50
Hello

Here around I can not find a 11.2896 mhz crystal, and order it by mail would cost me quite to much high price for the minimum shipping cost.

I only have a 11.275 mhz crystal and a 11.840 mhz crystal.

So I did think to use an oscillator that I can adjust a bit the frequency.

Thank

Bye

Gaetan
 

SgtWookie

Joined Jul 17, 2007
22,220

KL7AJ

Joined Nov 4, 2008
2,225
Hello,

A crystal oscillator can be "pulled" for a maximum of 700 ppm.
See the design notes in the PDF.

Greetings,
Bertus
And you REALLY have to work at it to get that much "rubber". I used to build VXO's, and by the time you got them working right, it was faster to regrind the crystals!

eric
 

bertus

Joined Apr 5, 2008
20,776
Hello,

As eric KL7AJ already told you, the old crystals could be grinded.
I used to do it with VIM on a glassplate, to get the frequency higher.
If you wanted a lower frequency you painted the crystal with black lacquer.

Greetings,
Bertus
 

KL7AJ

Joined Nov 4, 2008
2,225
Hello,

As eric KL7AJ already told you, the old crystals could be grinded.
I used to do it with VIM on a glassplate, to get the frequency higher.
If you wanted a lower frequency you painted the crystal with black lacquer.

Greetings,
Bertus
You could also use McClean's toothpaste instead of Vim. It goes without saying that anything that could grind quartz down probably did wonders for your teeth too!

Eric
 

Thread Starter

gaetan8888

Joined Nov 14, 2008
50
Hello

Looking at Crystals Oscillators

There is various types of Crystals Oscillators with different kind of output, which ones, in those output types can drive four 74HCT74 ?

Crystals Oscillators output types; TTL - HCMOS - LVPECL - LVDS - LVDS

Thank

Gaetan
 

bertus

Joined Apr 5, 2008
20,776

flat5

Joined Nov 13, 2008
403
How far can you bend a ceramic resonator. Is this a useful technique to get more spread that a xtal provides yet still have a good measure of frequency stability?
 

Thread Starter

gaetan8888

Joined Nov 14, 2008
50
Hello

Fox made the FXO-HC52 serie, a very low jitter ceramic resonator crystal oscillator, at very low price and seem quite interesting.

But is it true that the ceramic resonator crystal oscillator have less precise timing and do age more rapidely compared to the quartz crystal oscillator ?

Maby those new models of ceramic resonators crystal oscillator would be much better ?

Thank

Bye

Gaetan
 
Last edited:

leftyretro

Joined Nov 25, 2008
395
Hello

Fox made the FXO-HC52 serie, a very low jitter ceramic resonator crystal oscillator, at very low price and seem quite interesting.

But is it true that the ceramic resonator crystal oscillator have less precise timing and do age more rapidely compared to the quartz crystal oscillator ?

Maby those new models of ceramic resonators crystal oscillator would be much better ?

Thank

Bye

Gaetan
Quartz crystals will always be superior to ceramic resonators as it a material with a much high Q value.

Lefty
 
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