[time-nuts] measure zero beat

Lee Mushel herbert3 at centurytel.net
Tue May 8 01:09:54 UTC 2012


I haven't been following this thread so I suppose it has already been 
answered, but how are you measuring "zero beat?"

Lee Mushel
----- Original Message ----- 
From: "David I. Emery" <die at dieconsulting.com>
To: <jfor at quikus.com>; "Discussion of precise time and frequency 
measurement" <time-nuts at febo.com>
Sent: Monday, May 07, 2012 5:37 PM
Subject: Re: [time-nuts] Oh dear

> On Mon, May 07, 2012 at 08:28:41AM -0700, J. Forster wrote:
>> A crummy crystal oscillator zero beated to WWV is good to 1 in 10E6, a Rb
>> disciplined to GPS maybe 1 in 10E11.
>> Do you seriously think you, or anybody, can hear a pitch difference of
>> 0.001 Hz in the audio range?
>> A quartz crystal is plenty good for any audio application, IMO.
>> -John
> I completely agree, and far more significant than accuracy
> is jitter (phase noise) in maybe the tenths of a Hz to thousands  of Hz
> area.   This does modulate the sampled sound and perhaps is perceptable
> at very low levels.
> BUT Cesium, or Rb buys nothing in respect to phase noise
> in those ranges... really good quality quartz oscillators have much better
> close in phase noise than many Rb's or Cesiums...
> What Cesium and Rb buy is good performance measured over much
> larger taus... which cannot possibly have any impact on human hearing.
> -- 
>  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 
> 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - 
> in
> celebration of what could have been, but wasn't and is not to be now 
> either."
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