Products > Test Equipment
Unknown GPSDO but BG7TBL logo on the circuit board and OCXO !
cdev:
JBooth, congrats on your first post.
If it wasn't sold as a BG7TBL, my thinking is, it very likely isn't one.
A product could end up with a PCB that was literally copied from BG7TBL, but populated with different parts, that might have issues, like for example, those (vendor name omitted) OCXOs that in 2016 were supposed to be crushed but ended up being sold to people. Or ublox gpss that were sold as M8Ns but which actually were an M8 series but lacking a TCXO, and flash chip, so not firmware upgradeable and not really an M8N, more of a franken-ublox.
Leo Bodnar:
I don't know of any 10MHz OCXO that can be pulled 1000ppm.
More importantly - do you trust your scope to do these measurements? I would expect good OCXO to have ET steering range of only few Hz.
Leo
--- Quote from: JBooth on January 17, 2019, 12:52:18 am ---When the GPS lock is lost and the alarm light comes on, the frequency jumps down much as 10 KHz within seconds and drifts erratically around
--- End quote ---
JBooth:
--- Quote from: Leo Bodnar on January 17, 2019, 08:54:48 am ---I don't know of any 10MHz OCXO that can be pulled 1000ppm.
More importantly - do you trust your scope to do these measurements? I would expect good OCXO to have ET steering range of only few Hz.
Leo
--- Quote from: JBooth on January 17, 2019, 12:52:18 am ---When the GPS lock is lost and the alarm light comes on, the frequency jumps down much as 10 KHz within seconds and drifts erratically around
--- End quote ---
--- End quote ---
Yes, 10KHz momentary deviation is very unusual. I believe it was because I had multiple instruments connected to the output via an improvised set of jumper wires on a breadboard (since I don't have a BNC "T" connector at the moment). I suspect that the unshielded wires may have picked up some noise that caused a false count. With the GPSDO connected directly to the counter only, the count drops about 10Hz when GPS lock is lost and the red alarm LED comes on.
But there still remains a strange mystery: When I had the oscilloscope and the frequency counter connected to the GPSDO via oscilloscope probes to breadboard jumper wires, the GPSDO was constantly losing GPS lock every few minutes and triggering the >.1Hz error alarm LED. With the GPSDO connected directly to just the frequency counter with coax cable, it never lost GPS lock for several hours running. I even took the GPS antenna out of the window and put it under the workbench for several minutes and it never indicated that it lost GPS lock! Weird.
I'm wondering if the GPSDO 10 MHz output is not isolated or buffered adequately? That might also be a factor causing the jitters and pulsing on the output waveform.
Hans_18T:
Do you have a picture of the board (component side), just for comparison.
Also mind that for instance TurboTom reported that the 10MHz BNC terminal had not to be soldered to the PCB at all.
I use the antenna under the roof, the device "sees" 5 or 6 satellites with a SNR of 35 db or better.
cdev:
Photos would be extremely helpful in figuring out things like this- often taking much less time to figure them out with a picture than any other way.
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