LEILA is currently deaf

    • Official Post

    LEILA is currently somewhat deaf and the Siren marker indicating that a user is using too much uplink power is not working.


    Please continue to monitor your own signal and make sure that you do not exceed beacon level !


    Please respect the rules.


    Team is working on this issue and it will hopefully be fixed quickly.

    • Official Post

    just returned from Bochum, LEILA is back working.


    We found some issues in the receive section including LNB, some further investigations will be done before the AMSAT-DL Symposium next week..


    Nevertheless, it was frightening to see how much work Leila had to do now that she is back in operation. Some stations seemed to ignore Leila completely, maybe because they can't do full duplex? Others even felt disturbed.

  • Nevertheless, it was frightening to see how much work Leila had to do now that she is back in operation. Some stations seemed to ignore Leila completely, maybe because they can't do full duplex? Others even felt disturbed.

    This morning I had Leila trigger on signals that (confirmed on some WebSDR's) were clearly below beacon level.

    I made some signals myself to measure (signals that never triggered Leila before) but even signals 5dB lower would trigger it. So, Leila wasn't deaf, it was having morning temper issues.


    I should note that, at this time, the Goonhilly WebSDR cannot be used for beacon signal levels because the beacons are significantly below level (compared to the middle beacon at least). Right now, the middle beacon measures -72.4 dB. On the same Goonhilly, the lower beacon measures -80.1dB and the upper beacon -80.7 dB. So, the lower and higher beacon measure 8dB below the middle beacon.


    Looking at the IS0GRB WebSDR, the middle beacon is -70.2dB, the lower beacon -71.5 dB, and so is the upper beacon.

    This is how I remember the signals from a few months back .

    That (relatively) matches my own signal measurements, and that means the Goonhilly WebSDB cannot be used to qualify signal levels. This problem started after fix of the recent "GPS lock" issues; in any case, it makes the "signal measurement" thing a lot more complex.


    Another issue is that if one sends a carrier, Leila zero-beats on the carrier. If the carrier is made using a SSB radio, then Leila is outside the passband of the radio and I can't even hear it; it is 300 Hz below the low-end of the SSB passband.


    I would appreciate not having another "full duplex" discussion. There clearly are a number of other issues at play here too. It is volunteers who are keeping all this alive and Corona makes working on these things even more complex. Who is without sin throws the first stone!

  • Did a test last night with the Leila system, what I think is that the warning system is triggered by narrow banded signals in the SSB 2700 Hz window. Narrow banded in this context means that Leila performs the power measurement over a much narrower part in the window than the 2700 Hz (or so) that we use for SSB.


    The consequence is that you can transmit with the same power, but that a poor equalization of the transmitted power will trigger Leila. Too much bass or treble and Leila goes off, Equalize the same power and Leila stays silent. Whistle in the microphone and Leila becomes active. Insert a CW tone with the same transmit power and Leila is triggered again.


    I fully understand that we should stay at acceptable power levels but in the current implementation Leila is more of a power density monitor than a power meter. Power metering should consider what we use for SSB in my opinion. Otherwise you are penalizing users for poor modulation rather than excessive transmit power. What did the makers of the Leila system want to achieve? Where is the pass-band aspect in your power measurement? What does it mean, stay below the level of the beacon, in an acceptable SSB band or in a different band, what width are we talking about? Or did you also want to warn users that they are splattering?


    Please don't start the full duplex discussion again, yes I do that myself in both my permanent and my portable setup. We see Leila and act and this is how you find out how we believe Leila works.