Folks,
It has been pointed out to me that I left out one step in my stepwise
calculation for power - there is one more step to be added and that is
to divide by 2 one more time - that is usually done just after the
'multiply by the square root of 2' in the steps below.
Just one more reason I like to reduce the formulas before calculation,
it is less prone to mistakes than stepwise calculation. If you are not
familiar with formula reduction techniques, it is covered in High School
level algebra (or at least it was in mine back in the late 50s).
73,
Don W3FPR
Don Wilhelm wrote:
As a parallel example, consider the process for calculating power when
one knows the resistance and the peak to peak RF voltage. It is quite
possible to work at the solution one step at a time - divide the Peak
to Peak voltage by 2, then multiply it by the square root of 2 to
obtain the RMS value, then square the result and divide by the
resistance. Each step takes time, but if one reduces the formulas
necessary to do the same computation, and plug the values into the
resulting formula, the peak to peak voltage can be directly squared
and divided by 4 times the resistance to obtain the same result in
much less time than the stepwise approach. The same principles work
in any mathematical computation, including those used for DSP - no
magic, it is all in the math.
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