[time-nuts] General questions about making measurements with time interval counter.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

MY AIMS

1) Try to learn about the various statistical tests (ADEV, MDEV etc), and
how best to compare oscillators, by making some measurements on various
oscillators I have.

2) Investigate the short/medium term stability of the output of  various
bits of test kit. All are locked to GPS by feeding 10 MHz to their timebase
inputs, so long term drift should not be relevant.

These istrumuments are:

a) The GPS itself - primarily a test of the 5370B time interval counter,
distribution amplifier and general temperature fluctuations in the lab.

b) Other GPS(s) when I get 1 or 2 more.

c) 10 MHz to 20 GHz Microwave signal generator.

d) 0.001 Hz to 30 MHz function generator.

e) A VNA that will work at 10 MHz. Turn sweeping off

f) A VNA that has a minimum frequency of 50 MHz. Again turn sweeping off.

METHOD - Suggestion for improvements welcome.

* Where possible set all instruments to 10 MHz, which is the same as the
GPS reference. (Obviously since one of the VNAs will not go below 50 MHz, I
would need to use a higher frequency)
* Feed GPS to the start input of the 5370B TI counter and the DUT into the
stop input
* Use the 5370B time interval counter to measre the time difference between
one output of the distribution amplifier and the output of the instrument
being tested .
* Collect data from 5370B and use John's Timelab to plot various graphs and
try to understand the differences between the various statical measurements
(ADEV, MDEV etc.)

MY QUESTIONS.

1) Should I use the GPS to provide a reference for the 5370B time interval
counter,  or would it be better to use the internal OCXO? Currently I have
the 5370B locked to GPS too, but I am wondering if this is a bad idea and I
should run it from its own oscillator.

2) Is there any advantage in a 10 MHz DUT going into the start or stop
input? I assume that it is irrelevant, as long as the GPS goes into the
other. But maybe not.

3) If the DUT is higher in frequency (eg 50 MHz) than the 10  MHz GPS,  is
there any advantage in going in the start ot stop input?

4) If the DUT is lower in frequency (eg 5 MHz) than the 10  MHz GPS,  is
there any advantage in going in the start ot stop input?

Dave