[time-nuts] Why a 10MHz sinewave output?

Attila Kinali attila at kinali.ch
Mon Feb 6 08:56:38 UTC 2012


On Sun, 05 Feb 2012 19:50:28 -0800
bob grant <bobgrant at fastmail.fm> wrote:

> Why is 10MHz output of many sources or distribution amps in the form of
> a sinewave?
> Is it something to do with signal reflections or ease of isolation?
> 
> Since zero crossing detectors are susceptible to noise wouldn't a fast
> TTL square 
> wave be more appropriate for signal distribution within a equipment
> rack?

The advantage of a sine wave is that you have a single, bounded frequency.
A square wave has quite strong components at odd multiples of the base
frequency, theoretically going up to infinity. To get a "good" shape
of the signal you need at least the first three of the harmonics, resulting
in a seven times increased bandwidth need.

Beside of the more complicated handling of the higher frequency components,
you also have to think about dispersion of the signal if you go trough
filters or use longer cables.

			Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin



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