[Lowfer] Epson Question

[Bill Ashlock]

>So the formula ought to be V^2/2*R, not V^2/4*R.
>This has the feel of a big argument coming up :-)
>Bill VE2IQ

No way, Bill, you are absolutely right. When I did my P-P to RMS conversion 
of a +/- .5v square wave I left out the final step which is the sq rt. That 
changes the .25 factor to .50.

Thanks for pointing this out. Interesting how the RMS of a 1v p-p sine wave 
is only 1/4 that of a 1v p-p square wave.

This reminds me of a mistake one can easily make when they calculate the 
power into a high Q antenna (such as a loop) that originates from a typical 
Class D push-pull output stage. The load from the antenna is NOT equivalent 
to a resistance of equal value to the antenna load. This is because a 
resistor has a broadband characteristic that loads all the harmonic 
frequencies of the square wave, while the antenna does not. Because the 
current into the antenna is a sine wave, even though the driving voltage is 
a square, the V^2/8*R is the correct formula, where the V is the P-P of the 
sq wave from the Xmitter.

Bill A

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