[time-nuts] Why are 1PPS signals so skinny?
Rick Karlquist
richard at karlquist.com
Mon May 14 19:10:46 UTC 2012
Mark Sims wrote:
>
> My first inclination, if I were building a timing receiver, would be to
> make the PPS output a nice, symmetrical square wave. But pretty much
> all GPS timing receivers output an anorexic, dinky little heroin addicted
> supermodel sized pulse (from 1 to 150uS wide is typical).
> _______________________________________________
One reason might be that it is convenient to have AC coupled
hardware, with a reasonable low frequency cutoff. 1 Hz is
not a reasonable low frequency cutoff, which is what you
would need if a square wave were used. (Actually, to accurately
reproduce a 1 Hz square wave requires response down to .1 Hz
and preferrably .01 Hz, due to droop and phase shift distortion
issues). A short pulse will conveniently propagate though
the same sort of distribution amplifiers used for 10 MHz, 5 MHz,
100 kHz, etc.
Rick Karlquist N6RK
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