[ntp:questions] Re: Fingerprinting hosts by clock skew

Terje Mathisen terje.mathisen at hda.hydro.com
Sat Mar 5 14:24:27 UTC 2005

John Ackermann N8UR wrote:
> I'm guessing Dave was joking in his comments, but the frequency vs. temp 
> curve actually can provide a very accurate thermometer.  HP manufactured 
> one along those lines, with a crystal and oscillator contained in the 
> sensor and a frequency meter for the display, that had something like 
> 0.001 degree C resolution.  And, those of us who play with frequency 

I actually did exactly this for my Master's thesis:

A 2-3 m long single-mode optical fiber, with laser mirrors at both ends, 
and a single-mode laser source:

The resulting optical oscillator had a temperature sensitivity of about 
0.01 degree per resonnance peak.

Using a longer piece of fiber would have increased the resolution linearly.

> standards often see temperature related fluctuations even in units that 
> have ovens or double ovens.
> Another example is an antenna that I use to receive Loran-C 
> transmissions for frequency monitoring.  The antenna is up on my roof 
> and contains an FET preamplifier.  I've seen an 80 nanosecond diurnal 
> phase shift as the antenna warms up and cools down each day.


- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"

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