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Noise source won't turn on

Posted: Tue Jan 19, 2021 12:50 pm
by b.mayr.1984
I've received a new KerberosSDR beginning of January.

An initial test with the directionfinding function worked immediatley as described in the Quick Start Guide at

But I can not manage to get it running ever since. The reason is, that the noise source does not appear to be able to be activated anymore. Unlike shown below in the screenshot from the Quick Start Guide I don't see any spike from the correlation function in the ABS X Corr window anymore. Instead all the traces remain noisy without any distinct correlation spike (just like the system behaves if the noise source is deactivated intentionally).

As instructed in the guide, I did activate the logfiles in, but apart from the usual initialisation and termination log messages I don't see anything out of the ordinary.

  • Is there a way to further narrow down the problem with the correlation function / noise source?
    • Maybe by expanding the code to yield more logging information with regards to the noise source?

Best regards,

  • I just want to highlight that I use the same cables and power sources for all the test. Since I managed to get the unit working with these already I reason that they are not the problem.
  • I also checked the forum for all threads that mention the noise source, but couldn't find anything that relates to my problem.
  • I noticed that the metal housing of the KerberosSDR gets quite warm rather quickly. So I thought it could be a thermal problem. But also trying to get a cold unit to run was not successful.

Re: Noise source won't turn on

Posted: Wed Jan 20, 2021 5:13 am
by rtlsdrblog
The noise source is just activated via a GPIO so there's not much logging info from that.

When the noise source is turned on, there is an LED on the board in the bottom left which should turn on (you'll need to remove the metal case). Can you confirm if that turns ON?

Re: Noise source won't turn on

Posted: Wed Jan 20, 2021 4:13 pm
by b.mayr.1984
Hello Carl,

Thank you for the quick response.

Yes, the green LED at the corner of the board, next to the GPIO pins, toggles on and off with the Noise source ON/OFF checkbox in the Sync tab (see attached photo for when it is on).

But this does not have an effect on the ABS X Corr graph.

Other observations:
  • The RF cable that goes from the noise source to the distribution board does not show any damage.
    • The RF connectors seem to be properly connected.
  • To the naked eye the solder joints around the noise source area seem fine.
  • The JP2 jumper is shorted (as can be seen in attached photo). But a printed message on one of the circuit boards says "Please remove JP2 jumper for Raspberry Pi operation" (I in fact operate the KerberosSDR with a Raspberry Pi 4). The quick start guide did not mention JP2 whatsoever.
    • What is the purpose of the JP2 jumper?
    • Should I unshorten JP2?
Further questions:
  • Would it help to check certain voltages or signals with an oscilloscope?

Best regards,