QO-100 solar conjunction nearing!

  • A first for hamradio satellite operators: we will have our first solar conjunction nearing.

    The Sun will pass behind the satellite and generate a lot of radio noise in our receivers.

    The exact time and date will vary according to your location, but for me here (QTH Zuerich, HB9) QO-100 will pass in front of the sun next Sunday (March 3rd) on 10:21h UT. Only 0.2 deg Offset so well within the 1.xx deg of my dish and the 0.5 deg apparent diameter of the sun.

    Expect apparent transponder noise to drop.. reason of course will be system noise temperature rising. Looking forward to all your observations!

  • Interesting! I remember when I started receiving satellite TV that there were also events when the satellite passed through the earth shadow (during the night, of course) and the transponders were switched off.

    I have not heard about that recently so apparently there is enough battery capacity now to keep operating.

  • For the NB transponder, the noise floor is so high that I would not expect to see much difference in S/N of downlink signals. The situation with the WB transponder may be more noticeable as the transponder noise floor is at a lower level, so the sun may well cause a noticeable degradation.

    I'm testing a 76cm dish (for /P operation) and see about 5.5dB sun noise with it, measured using Spectravue continuum mode. The cold sky reference was at the same elevation as the sun. Clear blue sky conditions.



  • Hey I can use it to check the alignment of my yagi! Let's get out the solar eclipse glasses....

    Edit: ok this conjunction was within .6 degrees here so well within the beamwidth of my 80cm dish but I did not notice anything on the NB transponder receive.

    Maybe when I make a plot of the noise floor over an hour interval.

    I checked the alignment standing behind the antenna with solar eclipse glasses and it looks OK (see the silhouette of the mast over the sun but yagi not visible).

  • Hi Achim

    As expected, WB beacon dropped out here on my 76cm dish, which gives an MER of 6dB under clear conditions. Sun noise was measured yesterday as 5.8dB with this dish.

    At 1012z MER started to fluctuate between 6 and 5, with sun at 146.4/24.3 deg az/el. Satellite is 147.7/25.3.

    MER continued to degrade and I lost video at 1016:30 with sun at 147.5/24.7

    Video back at 1024:31 with sun at 149.6/25.3.

    MER back to 6dB at 1030 with sun at 151/25.7.