I recently came across details of this remarkable contact on the 1296 MHz (23cms) band.
On the 22nd January 2025, the PI9RD station at the Dwingeloo radio telescope facility in the Netherlands managed to make a contact with HB9Q in Switzerland by bouncing signals off an INMARSAT satellite in geosynchronous orbit.
While it is reasonably common for stations on the 1296 MHz band to bounce signals off the moon and for geostationary satellites like QO-100 to relay microwave signals, the signals on this occasion were physically bouncing off the metalwork of a geosynchronous satellite.
When you consider that satellites in a circular geosynchronous orbit are at an altitude of 35,786 kms rather than a few hundred kms for satellites in low earth orbit then it's even more remarkable.
Jan, PA3FXB gave this account of the contact...
Today at PI9RD (25m Dwingeloo telescope) we succeeded in completing two QSO’s on 23 cm with HB9Q via reflection off geostationary satellites.
This journey started in May 2013 when Andreas DJ5AR and I (PA3FXB) had our first 23 cm ISS bounce QSO using our 3 m dishes. We started experimenting with the big dish using smaller satellites.
In 2016 we (DJ5AR and PI9CAM) had a QSO via reflection off an old orbiting weather satellite. Since then, we started thinking of a QSO via reflection off a geostationary satellite. Much much, farther away but virtually fixed so no tracking challenges.
With HB9Q we tested using a cluster of ASTRA satellites using the double tone of JT65. We did not hear or see anything, but computer analysis showed that the signal was there! We did it again and got the same result. People familiar with the satellite world suggested us to use INMARSAT as passive reflector.
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| 120W into a 25m dish on the 23cm band |
The first INMARSAT-test with HB9Q was at the end of 2023 and produced a nice stable -23 dB and decoding signal on our screen. We then used Q65-120A. Our output power is much less so Dan did not see our signal and a strange thing happened: After a few minutes the signal disappeared….
Thinking about this and talking to satellite operators brought us to the conclusion that the orientation of the solar panels of the sats is an important thing to get good reflections. Nobody could tell us how it works on the different sats but there appear to be two systems. Constant moving of the solar panels and moving them in big steps every now and then. This might have happened when the reflection disappeared….
With this uncertainty about the solar panel position we decided to simply try a few INMARSATs. Today was the day ??
And some minutes later after sending our RR73’s several times we received 73 from Dan. So, we made it!!! Just barely but we made it ??
After that we tried two other INMARSATs but with no result at all. So, here we are, two QSO’s via passive reflection off two INMARSATs. We think this has never been done before by radio amateurs.
It made us very happy! Thanks to Dan and his patience and many tests!
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Well done to all concerned. For some details of other interesting contacts on the 1296 MHz band, see my Microwave page.
