Prop II Timing/clocks

swampie777

Will the Prop II have a more stable (lower error) oscillator? Accurate timing is essential to numerous capabilities. Maybe not a plug in atomic clock, , but at least a temp controlled XTAL.

Thanks,

Swampie777

Mike Green

No

The Prop II will have a similar oscillator as the current Prop I. If you need timing to that sort of accuracy, you should use a temperature compensated external clock oscillator or temperature compensated crystal. The Prop I (and presumably the Prop II) will work just fine with an external clock source.

swampie777

Thanks, Mike!

What external "more accurate" clock would you ( or other forum members) recommend?

heater

Depends what you want to do.
Accurate time keeping or just frequency generation can get quite expensive.

A Fluke precision frequency reference will probably set you back a few grand.

Or how about an Agilent Technologies (www.agilient.com) Model number 5071A atomic clock with a long-term stability better than 1 x 10-14 price - $50,390

But as you have a Prop why not make a crystal oven. The Prop can control it's own crystals temperature.

There are many such projects described on the net.

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For me, the past is not over yet.

swampie777

Heater;

My purpose is to increase the accuracy of measuring pulse widths over that which the Prop is capable now at a reasonable cost.

Thanks,

Swampie777

w8an

Heater's idea is an interesting one--a controlled oven, self compensating system. Perhaps it would be able to use the GPS system as a reference.

..Steve

Toby Seckshund

Back in UK Transmitter group we had rhubidium drives ( or rhubarb on our drive, can't remember now )

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Style and grace : Nil point

Mike Green

The Prop I has a resolution of one clock cycle for the use of the cog counters for measuring pulse width.· If you're careful about supply voltage and ambient temperature, you can run the Prop I at 100MHz to get a resolution of 20ns ("jitter of up to 10ns on leading and trailing edges of a pulse).· As the others mentioned, you have to use some kind of temperature controlled or temperature compensated crystal or external crystal oscillator to get reproducible accuracy on that order.· How accurate depends on what you want to spend to buy it.· Look at temperature compensated crystal oscillators from Maxim/Dallas for one example of a solution.· Go to any crystal manufacturer's website to see what kind of accuracy they provide at what cost.· They should all have temperature controlled crystals as well.

The Prop II will operate at a higher speed, so the resolution will be better, but the accuracy will still depend on the system clock source and you have the same sorts of choices for that.