[time-nuts] Another "atomic" clock question

[Tom Miller]

----- Original Message ----- 
From: "Hal Murray" <hmurray at megapathdsl.net>
To: "Bob Albert" <bob91343 at yahoo.com>; "Discussion of precise time and 
frequency measurement" <time-nuts at febo.com>
Cc: <hmurray at megapathdsl.net>
Sent: Sunday, March 02, 2014 2:45 AM
Subject: Re: [time-nuts] Another "atomic" clock question



bob91343 at yahoo.com said:
> Okay you want numbers. Well, I think 10 ppb or thereabouts should do it.
> Somewhere there is a discontinuity in accuracy plotted against cost and I
> don't want to cross that barrier just yet. If I can get 1 ppb without a 
> big
> increase in cost, I'll take that.

How good is your crystal?

Junk crystals are good thermometers.  Ballpark is 1 ppm/degree-C
If you are running ntpd, turn on loopstats and measure the temperature...
  http://www.megapathdsl.net/~hmurray/ntp/slope.gif

I've been watching a 3 MHz ovenized crystal.  It was something like 4 for 
$25
from ebay.  It's a 2 in sq can, over an inch high.  It's got a few ppb of
noise over minutes/hours and a few more ppb of drift/wander over 
days/months.
 It took several weeks to stabilize after power on.

-- 

Is that 3 MHz OCXO one from Ridge? If so, I opened one up and was surprised 
to find it did not have any foam insulation.

Tom