[time-nuts] Measuring 10 MHz
brooke at pacific.net
Thu May 8 08:54:48 EDT 2008
An important aspect is to properly set the trigger levels for each input.
A mistake I made early on was to ass-u-me that the 1 PPS trigger level should
be half of 5 Volts, i.e. 2.5 volts, but that's very wrong. The best approach
is to install a BNC-T connector at the front panel and use a scope probe to
look at the signal. The best place to trigger is at the steepest slope.
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Martyn Smith wrote:
> Thanks to all for your replies and suggesting especially Brooke, Bruce and
> I am already using the Stanford technique with the 1 kHz output. That's how
> I get 2 x 10E-12/sec accuracy.
> Using this technique, the accuracy should be 7.9 uHz at 10 MHz (7.9E-13).
> But I don't reliably achieve this. I reliably get 20 uHz, sometimes 10 uHz
> and I do have resolution to parts in 10E-13, but the last digit isn't
> Brooke do you do better than me here with this technique? I see you publish
> results with accuracy better than I can achieve, I was wondering how you do
> I think the answer from Bruce identifies my problem. I need to take more
> care with my measurement techniques
> If it was easy, people wouldn't charge $20 - 50k for a box that dies it
> Thanks all again
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