Thread: Help calibrating a noise source
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Old October 1st 06, 12:31 AM posted to rec.radio.amateur.homebrew
Roy Lewallen Roy Lewallen is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 1,374
Default Help calibrating a noise source
wrote:
. . .
Random noise voltage or current can ONLY be calibrated by
a TRUE Root Mean Square measuring instrument. By "true" I
mean a thermionic type such as an RF power meter (thermistor,
bolometer, etc. sensor). Few voltmeters on the market have
TRUE RMS measuring capability; those that do are specified
as such and rather on the expensive side.
. . .

Not too long ago, I got an HP3400A (10 MHz bandwidth) on eBay for the
purpose of measuring noise. Don't recall what I paid, but it was very
reasonable. Since truly random noise also has low-frequency
fluctuations, an RMS meter reading wanders quite a bit while measuring
noise. I find it easier to eyeball interpolate an average reading with
the analog meter of the HP3400A than with a digital meter.

Roy Lewallen, W7EL
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