[time-nuts] 9390 GPS RX

Ed Palmer ed_palmer at sasktel.net
Wed May 29 11:47:04 EDT 2013

On 5/29/2013 4:27 AM, Mark C. Stephens wrote:
> Well, what do you know, I turned it up on its end with the heatsink end on a heatsink and overnight it locked dead on 10Mhz.
> Well as far as I can go, 10Mhz exactly, to 10 digits.

Do you mean you didn't have a heatsink on it before?  That would be very 
bad.  It would cause overheating.

> Lamp-Volts=9.6

Very nice.  I've got 3 FRKs.  None of them have a lamp voltage that high.

> Crystal=8.2
> Lock=yes
> HDev=1.78E-12 @ 700 Seconds so it's still a teensy weensy wobbly.

How did you measure this?  Provide details, please.  I was measuring 
mine by measuring the time interval between the FRK and a Z3801A GPSDO.  
Then I realized that I might be seeing the GPSDO so I replaced it with 
my best OCXO.  After I remove drift from the results, I'm seeing AlDev 
of about 2e-12 @ 1000 sec. and still trending down after about 16 hours 
of runtime.  Total Deviation (Timelab doesn't have it) measures about 
9e-13 @ 10K sec.

> Long term stability is awful. 4.7E-11 @ 1:12 before I gave up on it while I was ahead..
> I wonder if the stability is correctable?

I'm not sure what you're saying.  4.7e-11 @ what?  I haven't studied 
long-term drift on my house standard, but I would expect that it would 
take a while for it to settle down.  In any case the 9390 will correct 
that.  If you log any data that the 9390 can provide you might end up 
with a good data record showing how stability changes with runtime.

> Also, I was 'gating' my timer to quickly before so some of the previous the readings have been out by miles.

Yes, one bad setting can spoil a data run.


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