I was listening to Minnesota Public Radio today, at close to 1PM CDT, when the announcer mentioned that twice a year solar activity is such that it can interfere with the station’s satellite transmissions to out-state stations. Today was one of those days, and people listening to radio stations that recieve their feed through a satellite feed might have experienced about 20 minutes of interference or loss of signal.
As we are still on daylight savings time here, this 20 minutes would closely correspond to noon, natural time.
So, what is special about today, and 1 other day of the year, that results in a bad satellite feed between the main MPR office in Minnesota and transmitters in other parts of the state?
Presumably this is when the sun is right behind (to within the satellite dishes’ beamwidth) the transceiver satellite. It seems to me that this should affect downlink by the receiving stations, though, and not the uplink to the satellite (since the satellite is looking almost directly away from the sun toward the transmitter at local noon). For a satellite in an equatorial synchronous orbit, this will occur twice a year, near the equinoxes but adjusted toward local winter (i.e., before the vernal equinox and after the autumnal equinox) by some amount depending on latitude (because at northern latitudes the dish must look slightly southward to the plane of the satellite’s orbit).
Yes - when the sun, the satellite and the receiving antenna are all in a straight line, you’ll experience “solar interference” or “solar outage” because the electromagnetic energy coming from the sun is many times stronger than what comes from any satellite, and the sun just “swamps” the receiver.
Fortunately, this line-up has to be precise, so it only lasts 10-15 minutes at a time, and happens at easily predictable times twice a year.