[time-nuts] OT: Power level reference

Poul-Henning Kamp phk at phk.freebsd.dk
Wed Dec 2 12:47:19 UTC 2009


In message <BA422CF5-53F0-443C-8AD1-EDC91A58464A at cq.nu>, Bob Camp writes:

>The accuracy / flatness of the detector is only one part of the problem. 
>
>In an RF system, the match to the detector can be a significant
>part of the error. If some of the power is reflected it messes up
>the reading ....

No disagreement from here on that.

What I played with, was a 50 Ohm termination a rotating mechanical
shutter and a IR sensor to see if it would be possible to level
three different frequencies to the same power-level, for calibration
of a HP3458A.

For this particular _relative_ power measurement, I think
the method has merits, it it may be possible to use it
to calibrate relative to DC as well, thus making the
calibration absolute, but I need to work on the mechanical
setup some more.

-- 
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.



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