[time-nuts] AM vs PM noise of signal sources

Charles Steinmetz csteinmetz at yandex.com
Tue Jan 9 07:36:31 EST 2018


Bill wrote:

> A switching regulator without the steep (and noisy) transients of
> today's switchers.

Well, don't get too giddy about how quiet the scheme is <smile>.  HP 
warned that if you use the same 12v (nominal) power supply for the oven 
control and crystal oscillator circuits, you need to add extra filtering 
to the oscillator power line to avoid injecting switching noise into the 
sensitive oscillator circuitry.

I always use separate voltage regulators for the oven control and 
crystal oscillator circuits when I build a 10544 or 10811 into a 
project, and I have modified HP instruments by adding an additional 
regulator for the oscillator section when they had 10544s installed, to 
good effect.  Even then, a small amount of switching noise is induced 
into the oscillator section internally to the 10544.

That said, it is a simple and robust system that performs quite well in 
general.

Best regards,

Charles





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