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.



  • I just calculated: When I use a 1meter dish and a pre-amp of 0.8db Nf. The VK3UM EME Performance Calculator gives a noise increase of 7.6 db.

    With a 0.8m dish -> 6.1 db noise increase.

    For my location the equinox is 09:55 UTC

    Assuming a beamwidth of 2 degrees (-3db points) the noise increase will start 09:51 UTC and ends 10:02 UTC. So 9 minutes or less.

    I'm curious now.

  • For me the maximum solar interference will be on the 13'th at 11:57 local (09:57 UTC). Interference is also observable 2-3 days before and after the max. event. Last time - half a year ago - I observed something like 5-6 dB increase in background noise looking 500 kHz below the transponder. This time I will watch the effect inside the transponder BW, which will be different due to transponders own noise floor.

    73 Ole

  • Hallo...

    is there any (maybe online) calculator for a given QTH (maybe Locator) and sat postion?

    would be interesting to catch the signal dropout....

    EDIT ... i was not online today ...but see the answer now in this thread 6hours below... sorry for bandwitdth

    73 de dg0opk

  • Can we change the title to Conjunction and not Equinox? I want to do this on a sunny day so I can see the clearance (or not) of vegetation.

    Is there a different calculator? I refuse to visit sites that do this:

    I absolutely do not trust anyone who would do this not to be a source of malware.

  • I am using my swiss army knife for satellite work: Nova for Windows.


    It is free. Also runs on Linux under wine..

    The sun is a standard object and the kepler elements of Es-hail2 can we loaded from https://www.celestrak.com/.

    With this program I can view the conjuction of Sun and QO-100 live by putting both objects in the current view. And make a planning.

  • Hallo ...

    today i could detect the first sun outtage NOISE on the WB-TP Monitor on my backup system with 85cm TV dish (centered to ASTRA 19.2) with an additional LNB to 26east. (effective dishsize is maybe 70-75cm)

    Maximum SUNOUTAGE is calculated for the 11october2019 on my location...

    so lets see was going on...

    picture attached with todays maximum at 10:06 UT

    73 de dg0opk