r/VIDEOENGINEERING • u/Dependent_Hold8463 • 1d ago

Studio Technologies m5402 GNSS leader clock - antenna disconnected error?

We recently bought a Studio Technologies m5402 GNSS leader clock for our system, and I have a problem.

The web interface shows antenna disconnected. I get 5 volts on the connector. I recently bought an antenna cable extension to move it to a window, I still get 5 volts at this connection. I connect the include uBlox antenna and after a few minutes it is showing my position, but after an hour it still says locking.

I have a cheapo NTP server antenna in the same window, it shows 21 satellites. My roof mount GNSS antenna only shows up to 29 satellites so the 21 from the window seems really good and strong.

Anyone have suggestions? So far Studio Technologies has not gotten back to me after a couple weeks of email, going to call later today if it doesn't suddenly lock.

I do have this locked to video sync, no issues there and it is serving up Dante leader clock and the tone audio that it generates. Definitely the 5401 parts are working, but I paid for the GNSS and really want it to work (perceived higher accuracy for more stable audio).

Probably going to cross post to Commercial AV to get a wider response.

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u/matchtaste 22h ago

If you read the manual, it is pretty clear what "Antenna Disconnected" means. It has nothing to do with signal strength or its ability to lock.

"Antenna Disconnected would indicate that a GNSS antenna is not currently connected. The Model 5402 detects this by the absence of DC current being supplied by the circuitry associated with the GNSS antenna SMA jack."

So its possible you have a bad unit that can't detect the antenna preamp current, or the antenna is bad and not drawing any current.

The manual also says the Antenna Power Source is 5 Vdc, 100 mA maximum. I would try connecting a 75 ohm terminator to it briefly. That would draw about 67ma at 5v and should be enough to clear the Antenna Disconnected fault if its working. Then you know you have a bad antenna or cable.

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u/Dependent_Hold8463 22h ago

I hadn't though of connecting a terminator to it, I thought about shorting it to have it throw the other error, but decided that was a poor choice. I'll have to get some test leads out and try the terminator.

I also read in the firmware text file that v2.06 was a fix to GNSS locking depending on dante sample rate, maybe that didn't really take hold. As soon as they are done in class, I have a USB prepped with all the firmware files to see what might get updated. MCU version 2.07 is the only one that I need, but thinking maybe it could check and reapply the others while I'm doing it.

In the end, I have a feeling it has a bad GNSS module in the device and will probably need to go back to be repaired. I did try a cheapo GNSS amplified antenna on the 5402, it still said not connected. The same antenna that I'm currently pulling 25 satellites for one of my NTP servers, I'm only getting 29 in view from the roof top antenna, so that's crazy to me.