[time-nuts] 9390 GPS RX

Mark C. Stephens marks at non-stop.com.au
Fri May 31 07:24:24 EDT 2013


Hi Ed, 


> Well, since you've apparently given up on time-wasters like sleep, there are a few things that you can do while you wait.
My daytime job is level 2 remote support so I seem to get by on about 6 hours sleep every couple of days.
Dunno how that works, it probably isn't healthy. The good thing is I get to work from home. And work they make me :)

> 1.  Check your power supplies for noise, ripple, and proper value. Not just the 28V, but there has to be 5V, maybe +-12V or +-15V, etc.  Don't forget that you've got capacitors in there that are over 20 years old so anything's possible.
> 2.  Check the EFC to the FRK for noise & ripple.

I'll get back to you on the PSU and EFC measurements later on tonight if I can sneak out. 
It is 9:30pm Friday night here and I have a deal with Mrs Wife, weekdays, I can work late but weekends must be spent as family time. Fair enough too :)

> 3.  Are there any software commands that have to be or should be used to set up the disciplining?  I glanced through a manual for a 9390 and it looks like there's a 'z' command to initiate disciplining.
I have only found 3 commands that work over the serial port "!", "#" and $.
It spits out a bunch of numbers periodically but they aren't corresponding to anything on the display.
I assume the Serial commands are pretty primitive on this early model.
Certainly z does not work.

> 4.  Do the status reports indicate that everything's good?  Number of satellites tracked?  Signal strength?  EFC value?  Anything else?
When doing GPS corrections, the 9390 always sees at least 4 birds which I think is its maximum. Nothing on SS I am afraid.
You remember I have to use a N to BNC adaptor with a BNC "tee". I have a 75R terminator in one end and a Nokia L1 antenna in the other.
That's the only way I can lose the <ANTENNA FEED ERROR>
I have set it to "Auto" mode. So, when the HDOP gets low enough it picks a satellite and switches to timing mode.
Then I start to see the EFC values. I am upstairs at the moment and unable to see the LCD.
Perhaps a web cam would be the ideal tool in this situation ;))
What I have done is run Time-lab remotely and I am getting 2.98E-12 for an hours samples and it was still dropping at the end of acquisition..
And although the frequency is constantly varying, how can the phase be so good?
Am I missing something here? Is it jumping 360 degrees or something?
Wrap around? I am at a loss, I am afraid.

One thing I noticed is the Lock LED (decimal point) is significantly brightest and clearest LED on the panel.
Either it has not been on for a long time or the series resistor has gone walkabouts.
As it is muxed, it must be the former, we can give ourselves a pat on the back for that one, Ed :)

> I'm looking at the picture of the unit on your website and I'm a bit confused.  I see the FRK in the back corner, but I can't see it's cabling.  I see what looks like an OCXO on the second board from the front with white cables coming 
>off of it.  There's also what looks like the outline of an OCXO on the main board with white cables connected where the output and EFC would be.  What's connected to what?

The FRK cabling comes out on the side facing the main board at the bottom. The EFC and 10Mhz go to the outline on the main board you so observantly noticed.
The "card" has a 16.618 (I think from memory) OCXO that goes to the main board on the 2 white SMB cables closest to the front. 
The next 2 SMB cables go down to the monster GPS RX mounted upside down under the main board platform.
This seems to be the reference for the GPS and the logic board is doing something with the clock to steer the GPS in some way.
I must put a 4 channel scope on and have a goosy gander. The only 4 Channel scope here is a rather ancient HP 180 series with a monster screen.
I think I have one of those early horrible 4 channel sampling HP scopes here as well. Anyway, I digress as usual..

> By the way, in the back right corner of the main board next to the EPROM, I can see a big Dallas Semi chip.  Are you aware that there's a lithium battery in there that's probably stone dead?  I don't know what the effect of that 
> would be, but it's something to check.

Upon Power up All settings are lost, error 17 - Battery Failed.
The battery is a as dead as a dodo I am afraid.
I have my eye out for the same type, I have found a few but the last 2 Digits of the Dallas part number differ even though they look the same.
As it has a sealed Lithium Battery (Who's smart idea was that then, I wonder?) I may have to buy a new one, perish the thought ;)

I powered the 9390 off in the afternoon for 30 minutes and when powered back on, I left it with default settings.
The Rubidium locked within 5 minutes this time. Must have been still a bit warm.
After about 20 minutes it had even found its location and was pulling down the satellite data.
So, Although inconvenient, I can live with that.
However if it holds self-calibration details that is a different story.
You have me pondering again, as Usual, Ed :)


-marki

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Ed Palmer
Sent: Friday, 31 May 2013 3:58 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] 9390 GPS RX


On 5/30/2013 9:44 PM, Mark C. Stephens wrote:
> Oh No, it stayed locked, I sat there until 4:30am watching it..
> But it's still drifting +/- 2 Hz 8 hours later which annoys me so much!
> I will take a page from Ed's book and exercise patience, I guess.
> Not much else I can do without disturbing its natural course.


1.  Check your power supplies for noise, ripple, and proper value. Not just the 28V, but there has to be 5V, maybe +-12V or +-15V, etc.  Don't forget that you've got capacitors in there that are over 20 years old so anything's possible.
2.  Check the EFC to the FRK for noise & ripple.

I'm looking at the picture of the unit on your website and I'm a bit confused.  I see the FRK in the back corner, but I can't see it's cabling.  I see what looks like an OCXO on the second board from the front with white cables coming off of it.  There's also what looks like the outline of an OCXO on the main board with white cables connected where the output and EFC would be.  What's connected to what?

By the way, in the back right corner of the main board next to the EPROM, I can see a big Dallas Semi chip.  Are you aware that there's a lithium battery in there that's probably stone dead?  I don't know what the effect of that would be, but it's something to check.

Ed


>
>
> -marki
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of J. L. Trantham
> Sent: Friday, 31 May 2013 12:32 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] 9390 GPS RX
>
> So, probably means that it is 'flashing', on and off. :^).
>
> Joe
>
>
> So, it's been sitting there for a couple of hours before the Lock LED came on.
> Interestingly enough, I woke up (its 3am here) and I thought, Hmm wonder if its locked.
> I walked down stairs to the workshop and looked at the front panel just as the Lock LED came on!
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