[time-nuts] "The Penultimate HP5065 A15"

[Poul-Henning Kamp]

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timeok at timeok.it writes:

> Another important point is that of the certainty of the results
> of a change. I mean that most hobbyists who have a 5065A, including
> me, do not have the opportunity to measure the proposed improvement
> effects, first of all because they do not have a reference such as
> an HMaser available, nor even such a refined measuring system to
> appreciate the improvements made.

Well, this depends exactly what you mean by "measure".

There is a big difference in being able to measure, with proper
uncertainty intervals, that "A is 7.2% better than B", and merely
measuring that "A is better than B (by some unknown amount)"

Let me give you a concrete example:

I am not kitted out for measuring close-in phase-noise.

But if I feed two signals of *very* close frequency to my HP5370,
hit "TI", "SAMP=100", and "STDDEV", then it shows me a number which
correlates strongly with close-in phase-noise.

If after modifying one of the two signal sources, that number drops,
I have solid evidence of an improvement in close-in phase-noise.

Mind you, I could have improved the phase-noise a LOT, and still
see the same number, if the phase-noise of the other source dominated.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.