Paul Burridge wrote:
If this is a misconception it must be an extremely widespread one. I've
found a reference to RMS power and how it's calculated in 'Practical
Radio Frequency Test & Measurement' (Newnes) and have posted the
relevant page he

http://www.burridge8333.fsbusiness.co.uk/cvcvcv.gif

If we are wrong, it appears we're not alone...


Any fool can write a book that includes the words "RMS power". I've done
it myself.

I have known since age 15 how to calculate the average power or an
arbitrary AC waveform: "Take the root-mean-square averages of the
voltage and current first, and then multiply those results together.
Doing it the other way around gives the wrong answer, stupid boy!"

My particular mistake was to try to use "RMS power" as a shorthand
label. I naively assumed that everybody would understand that it was
short for:

"This is power that has been calculated by a *correct* use of RMS
averaging, which we all know means taking the RMS average of the voltage
or current first, and obviously it does not mean taking the RMS average
of the power, because that would *not* be correct, and now that we've
wasted half a paragraph on this point, and completely derailed the
original train of thought, which was mostly about something else, I'd
rather like to get back to our main topic."

Just writing "RMS power" seemed so much more appealing...

BIG mistake! It fell right into the gap between people who don't know
how to calculate power correctly; and people who do know, but were all
too eager to assume they'd found a fault.

I learned from that mistake... but the mistake itself is immortalised
6000 times over, in cold type.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek