[time-nuts] M12+ Temp sensitivity

Randy Warner Randy at synergy-gps.com
Tue May 2 20:53:51 EDT 2006


Said,

Hey! Whaddya mean CHEAP? The marketing guys call it feature laden and
cost effective!

Anyway, you're right. The M12+ is extremely sensitive to environmental
stimuli. On our receiver/adapter board assemblies I actually include a
piece of foam tape between the two boards that gives the crystal
(crystal, not TCXO) some isolation from the outside world. The old
original M12's actually worked better in this respect because they were
in a normal crystal can which lengthened the thermal time constant
enough that temperature perturbations weren't a problem. The SMD Rakon
crystal used by current M12+'s just doesn't have any sense of humor when
it comes to temperature changes.

The new M12M's DO HAVE a Rakon TCXO and are a lot more insensitive than
the M12+'s. 

Randy

________________________________________________________________________
_________________________________


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of SAIDJACK at aol.com
Sent: Tuesday, May 02, 2006 5:34 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Question on disciplining oscillators

Hello James,
 
I noticed that the M12+ has a significant temperature sensitivity,
especially when air is flowing over the TCXO. Try blowing air onto the
TCXO, I  have seen the 1PPS immediatly wander off by much more than 50ns
before the M12+ shuts-off the 1PPS output.
 
Maybe you are seing the M12+ react to environmental effects?
 
After all, the M12+ itself only disciplines its internal (cheap) TCXO to
the GPS signal, and is thus itself a slave to the TCXO sensitivities.
 
I wonder how much better the M12+ would be if the internal TCXO is
replaced by an external high-quality OCXO...
 
bye,
Said
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