Birdie above Upper Beacon on 10490.0 MHz

  • pe1hzg

    I can confirm the carrier. It has been on the upper beacon since day one. The carrier is not visible/audible on the IS0GRB websdr. That's indeed a bit strange :-) Like DK8KW said this looks like a locally generated carrier. My RX setup is similar to the setup at Goonhilly, we both use the AIRSPY SDR. Another mystery to investigate ....

    de Greg DF2IC

  • for those with extra carriers: have you locked your setup to an external reference? 10490.000 is an even multiplier when running with 10 MHz ref so it might be an internal birdie.

  • See attached picture, IF-display, yellow arrow. Are we talking about this? This is even there, when i remove power from my lnb, so i suspect

    it is generated in the RTL-dongle. Depending on the accuracy of the 25Mhz reference fed to the lnb, this carrier was above the beacon before i removed power, was there when power was removed and is there below the beacon now that i restored power. It is slowly drifting further down and i am sure it will be above the beacon again when everything has warmed up again. No 10Mhz reference here when i tested it, just a homemade 25mhz reference , rtl-dongle and sdr-console. I have an older screenshot from a while back before the transponder was widened up, the carrier already was there. Will make another screenshot when it has moved to it's "original" position.

  • Hi Martin, yes I think that is it. If it stays without LNB power, it's certainly a RX birdie. Try to change RX frequency a few 100 kHz up and down, for me this changes the absolute birdie positions significantly (they might be aliases of the digital sampling).

    The joy of digital receivers :)

  • Hi Achim,

    i just heated up the dongle with a heat gun, the carrier drifts all over the place and is now back to the position it was before . So at least in my case, the culprit is the dongle. YMMV

    Greetings from your hometown..

  • DB2OS

    Changed the title of the thread from “Extra carrier in top experimental beacon?” to “Birdie above Upper Beacon on 10490.0 MHz”.