[time-nuts] 9390 GPS RX

Mark C. Stephens marks at non-stop.com.au
Wed May 29 11:58:05 EDT 2013

Uh, well. No one told me about the heatsink thing :)

I am using a HP5370B.
I am comparing to my best GPSDO.
For instance my 5x Z3805A's get down to the low -12's after 1 hour.

4.7e-11 at 1 hour 12 minutes.

Do you think the FRK is ready to go back in the 9390 :)
I hope so, I like that 9390 and I want it in my rack :)


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Ed Palmer
Sent: Thursday, 30 May 2013 1:47 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] 9390 GPS RX

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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