Dear Joe,
On 2022-02-13 23:31, Joseph Gwinn wrote:
On Sun, 13 Feb 2022 03:30:30 -0500, [email protected]
wrote:
time-nuts Digest, Vol 214, Issue 15
Attila,
Date: Sat, 12 Feb 2022 20:38:48 +0100
From: Attila Kinali <[email protected]>
Subject: [time-nuts] Types of noise (was: Phase Station 53100A
Questions)
To: Discussion of precise time and frequency measurement
<[email protected]>
Message-ID: <[email protected]>
On Fri, 11 Feb 2022 18:25:05 -0500
Joseph Gwinn <[email protected]> wrote:
May not realize that thermal noise (additive) and phase
noise (multiplicative) are not the same, and do not behave the same.
It seems like you are mixing up here quite a few different concepts:
Phase noise vs amplitude noise, additive vs multiplicative noise,
thermal vs other noise sources, white noise vs 1/f^a-noise.
You are right of course. I was using shorthand.
A better word than multiplicative is parametric, the varying
parameters being path loss and path group delay. This is as seen at
the phase noise test set.
All these are orthogonal to each other and you can pick and match them.
I.e. Phase noise can be additive, 1/f^2-noise and thermal.
At the generator, certainly. But the downstream PN test set may not
be able to tell. More later.
Amplitude and phase noise are looking at noise from two different
perspective. One is how large the variation of the peak of a sine
wave is, the other is how much the zero crossing varies in time.
Note that all natural noise sources will be both amplitude and
phase noise.
Hmm. One case I'm interested in is where the path attenuation varies
according to a random telegraph waveform, due to for instance a loose
connector or cracked center conductor rattling under heavy
vibration. In this, the electrical length does not change. While
the source of the carrier whose PN is being measured will have some
mixture of AM and PM characteristic of that source, the residual
(added) PN will be characteristic of the transit damage encountered
between source and PN test set. So wouldn't this randomly varying
attenuation yield mostly residual AM PN and little residual PM PN?
Actually, measure vibration inpact like this have a long tradition and
is indeed possible.
It may or may not be an effective method thought. As suggested by
others, TDR may very well be more effective method to locate impedance
errors. Could be that they add good information for different errors.
Also, recall that errorenous connectors can create passive
intermodulation distorsion (PIM), which is readilly measured using the
two-tone method.
I would use a wealth of methods to attempt different techniques and see
what they excell at and not.
I would not assume the random telegraph waveform variation. I would
rather learn from reality the types of variations you see.
I think you should consider two different phases, detection of problem
and location of problem. When it comes to location finding, TDR excell
at that. AM measurements as well as PIM is relevant for detection of
problem as well as verification.
I would recommend you to look at the updated IEEE Std 1193 when it comes
out. There is improved examples and references in it that may be of
interest to you.
It may be beenficial to stick accelerometers here and there to pick up
the vibrations, so it can be correlated to the measured noise, at it
could help to locate the source of the noise and thus help with locating
where, more or less which engine that was causing it.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- [email protected] -- To unsubscribe send an
email to [email protected]
To unsubscribe, go to and follow the instructions there.
