GPS broken [fixed with software reinstall, root cause not understood]

hey :)

My Kiwi unfortunately receives GPS only very poorly, it hardly comes a fix to stande. You can see sporadic satellites in the admin interface, but no stable data. I thought, okay - maybe the GPS receiver is broken. Have the new now connected, the same problem still occurs. Do you have any ideas? Should I reflash the Kiwi once? Any Ideas?

73 DO1DSH

Dennis


Comments

  • Describe the location of the GPS antenna

  • I can also put the antenna under the open sky, that won't change much. It has also worked properly before, the whole list was full with the receivable satellites. And there was a GPS fix without problems.

  • if you have a voltmeter, check to see if bias DC is coming out of the GPS antenna connector on the kiwi cape

  • How long is the coax, Is it a single piece, is there around 3V on the GPS SMA centre pin?

    Is anything else close to the coax/antenna? (mobile or dect phone, motors etc)

    Is it the same after a Beagebone reboot?

  • The 3.3V of the SMA socket of the GPS antenna are present. I have already tried several restarts of the entire KIWI. Last idea would be to restore the emergency image from the SD card and hope that this solves the problem.  

  • do have or can you borrow an alternate GPS antenna to try? Any 3.3V active one should work

  • I already tried an another GPS Antenna, same behave.

  • OK so about the coax, antenna and items close by? We need to know what to discount as "recently tested good" (ideally on another system).

    GPS is not a massively strong signal if something is wiping it out you would see what you do now, have you tried a phone app like "GPS Status" (Android) to check all is well locally? (bear in mind mobile phone GPS's are horribly good now). I just started the app on my three year old phone and it had about eight satellites indoors (from cold) in the time it took to type the last two lines.

    From previous experience I would be surprised if it is software as there are many more physical things that can break GPS than software if it works to some extent.

    WA2ZKD
  • The problem has been going on for 2 weeks or so, I can't say for sure. I only know at the beginning when I put the Kiwi into operation, the GPS ran as I expected. At some point I noticed that he no longer gets a fix and then I tried some things and thought that the GPS receiver is broken, I have now replaced, but that does not seem to be the case. Just looked again, even if the GPS antenna is attached, is still 3.3V at the SMA socket. So voltage does not break in or so. 

  • Was your other GPS antenna also an "active" antenna with at least +28 dB gain?

    The display you posted is the same as you'll get with no antenna connected, i.e. how it is responding to noise at the input. RSSI readings below about 300 are just the software desperately searching for a signal acquisition through all the noise. If the "subframe" blocks are not turning colors then no satellite signal is being received.

  • After installing the emergency image, the GPS is running again. No idea what exactly the problem was...


  • I had a similar case in August. On both receivers I only received one gps signal, which was very weak. Everything returned to normal by itself after 3-4 hours. Antennas glued to a metal roof 10m above the ground. In my opinion, it was either due to the heavily charged storm fronts at the time, or someone in the area was playing jamming the signal. To this day, the situation has not happened any more.

    The best of 2021

    greetings

    Powernumpty
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