"Richard Clark" wrote in message
...
On Sun, 6 Feb 2005 15:59:36 -0000, "Dave" wrote:

leading edge of a step from 0 to some 'static' value

Hi Dave,

...negates the usage of "static" - clearly.

A step pulse is not "static" and in fact contains an infinite range of
frequencies all of which are NOT DC. This is called the genii out of
the bottle and no one here can (but no doubt will try to) put it back.

73's
Richard Clark, KB7QHC

you will of course note that i quoted the term 'static' to denote that it
was indeed not static in the infinite sense of mathematics, but in the real
sense of it being a constant value over some measured time period.

the other obvious thing you are missing is that DC is a frequency... and it
does come out in the Fourier transform as a frequency of zero with some
finite magnitude for any waveform who's average value is not zero. it does
not even require that the waveform stay at some value forever, a short pulse
going from 0v to 1v and back to 0v will have a DC component in its spectrum
both mathematically and on any meter that can properly respond to it.