[time-nuts] GPSDO control system

Bill Hawkins bill at iaxs.net
Sun Mar 23 05:06:00 EDT 2014

An idea is struggling to take shape in my fevered brain.  I'd like to
check some foundation assumptions.

1. The difficulty with disciplining a local oscillator to a GPS signal
is due to variations in the received GPS signal and the LO.

2. The variations occur slowly, as crystal aging, and quickly - perhaps
sawtooth or crystal crack propagation - and maybe something in between.

3. The gain of the system, in degrees of phase angle at 10 MHz (or
higher) per microvolt of control signal, is fairly constant in a
controlled environment.

4. The power supply for the device providing the control signal cannot
be regulated to the accuracy required of the system, and so is a source
of variance. (Does anyone put the voltage reference device in the oven
with the crystal?)

5. The principle source of environmental variation is temperature.
Humidity and barometric pressure are not significant. This may not be
true of the received GPS signal due to atmospheric variations.

6. A digital computational device is available to calculate the control
signal from various measurements and previous values.

7. There are no supernatural forces at work, such as the experimenter
mentally influencing the results. :-)

That's a start . . .

Thanks for any replies.

Bill Hawkins

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