[time-nuts] Another "atomic" clock question

Bob Albert bob91343 at yahoo.com
Sun Mar 2 14:56:45 EST 2014


Thank you for your comments.  I see the situation a bit more clearly now, and will do some searches on Trimble and GPSDO and so on.  Right now I am interested in seeing what my options are, and deciding which way to go.

Yes this can become an obsession but I keep reminding myself that it's a hobby and isn't stopping me from eating or sleeping or breathing.  I do have fun with it.  Recently I bored a couple of visitors showing how my counter and signal generator drifted during warmup but eventually settled within about 10 ppb of one another, within about a half hour.  (Both units have 24/7 ovens.)  The generator actually accounts for nearly all the drift.  The counter is a venerable HP 5245L with 500 MHz plugin.


On Sunday, March 2, 2014 10:33 AM, Tom Miller <tmiller11147 at verizon.net> wrote:

----- 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...

I've been watching a 3 MHz ovenized crystal.  It was something like 4 for 
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 
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.


time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

More information about the time-nuts mailing list