> I haven't seen an analogue 'scope guaranteed to an accuracy of better than
+/-5%
> of full screen. That means a possible power error of around +/-10%,
excluding
> probe errors. Digital ones can get to 1%, although you have to watch
analogue
> bandwidth ratings, and aliasing problems if you're not running single
tone. Add
> the probe error too. Any of these methods requires calibration against a
known
> power source at the frequency of operation.
>
> 73
>
> Peter G3RZP
Any indirect measurement, i.e. evaluating RMS power through a voltage, needs
calibration.
So called in-line wattmeters are actually voltage/current meters, presume a
sine wave is applyed and the SWR is 1:1.
Detecting a peak voltage allows DC measurement but introduces other
parameters (linearity) that have to be corrected (diode curve and
capacitance) so making a useless feature inherent voltage meter precision.
All considered an oscilloscope is not so bad or worse.
73,
Mauri I4JMY
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