[time-nuts] Low noise power supplies?

[Charles P. Steinmetz]

Bob wrote:

>An AD 797, a couple of metal film resistors, and a fairly large (say 
>47 uf) plastic cap work pretty well.

The band from 10 Hz down to 0.1 or 0.01 Hz is generally important 
when testing oscillators.  To keep the 797 input noise density below 
a few nV per root Hz, the terminations must have very low 
resistance.  With such low resistance, a 47 uF cap won't even get you 
to 10 Hz, much less 0.1 or 0.01 Hz.

One more thought: Many oscillators have internal regulators that are 
not nearly as good as what you can build.  No sense using an external 
supply with 5 nV per root Hz noise density if it will be re-regulated 
inside the oscillator by a circuit that has a noise density of 250 nV 
per root Hz.

Best regards,

Charles