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($40 GPSDO working well now, my mistake)

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cdev:
Edit: Old title was: GPSDO loss of satellites+fix troubleshooting
New title: True Position GPSDO working well now

Original post: What would you look for as broken/fixable in a GPSDO that:

1.) fails to lock on more than 1-3 satellites at a time, and that with extreme difficulty.
2.) wanders in terms of temperature and seems very hot (upper 40s C.)

The antenna and signals are known to be good, so its not that. It currently has around a 50% sky view.

Note: I should have known better.
The GPSDO was never broken, it was my dumb mistake, its a semi old GPSDO, and it needed to have a big and expansive sky view to be happy, which it wasnt getting in my windowsill. Moved to the middle of the back yard, it got seven sats.

its happy and working well now (and these GPSDOs, which were used in cellphone E911 radiolocation, are a great value.)

ConKbot:
What the c/n numbers (signal strength or SNR potentially) for the 3 satellites you do lock? A good antenna/lna/rx should pull C/N numbers in the high 30s to low 40s for satellites in good positions, and in the 30s for the rest of a reasonable constellation, with a few satellites (maybe on the horizon) in the high 20s.

If you're only getting lock on 3 or so and they are in the 20s, something is potentially wrong with your antenna/lna/cable/rx front end.

edpalmer42:
Cdev, you know better than this!  We can only give vague general suggestions when you give us vague general info.  What type of GPSDO is it?  Can you talk to it?  Any error messages?

Ed
 

cdev:
Its a True Position cellphone radiolocation board. Telecom surplus, apparently.

It looked like too good of a deal to pass up.

And now its working better, much better.

So, (crossing fingers) maybe that was it!

Wow, now seven satellites.. things are looking good.. 


Thank you!

cdev:
Its a telecom surplus unit that was made in 2008. It contains a Bliley OCXO and Furuno GT-8031 timing GPS.

It cost me around $40! 

What do you get?

 The bare board. It requires 12 volts of power and you need to talk to it via 3.3 volt UART or RS-232. When it boots, you have to enter in $PROCEED and then it starts receiving.

There are a number of commands that are possible which are detailed in a PDF at packratvhf.com  There was a thread in May mostly about them on the Time-Nuts mailing list.

Now the fun part starts, building a device around it.

There is an "$EXTSTATUS" message which is not documented in the PDF which contains the number of satellites tracked.




Quote from: edpalmer42 on Today at 10:43:52
Cdev, you know better than this!  We can only give vague general suggestions when you give us vague general info.  What type of GPSDO is it?  Can you talk to it?  Any error messages?

Ed

--- End quote ---

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