Communicating on VHF via reflections from the International Space Station ISS

Making things difficult... without adding digital communications..!

The other day, Håkan SM7WSJ suggested that we should try to communicate on 144 MHz by reflecting signals off the ISS. To me this sounded like quite a challenge, and we set out to do some testing. Both were using our EME systems.

Contrary to my belief, signals were indeed heard, but funny enough not by the two stations involved, instead it was Frank PE1NFE who heard us and made a recording. This was on Friday, November 30, 2007. Frank is using a single yagi.

Here you can listen to Franks recording


One can clearly identify the two calls "SM2CEW SM7WSJ", and this is probably SM7WSJ's transmission that Frank recorded. Note the huge doppler shift on his transmission.

The following night, December 1, 2007 we made two attempts as the ISS was in a favourable position. Many stations in Europe were listening to us, and some even heard us. I recorded the 2nd attempt, and have made two MP3-files out of the full wav-file that is >9 Mb. A couple of fellows also made recordings, and I will update this page with their recordings when I receive them.

We were using EME procedures and 30 second periods. Håkan was just missing my RRR to make it a complete QSO. In future tests we will use shorter periods. It is very difficult to follow the signal for a long time as the doppler shift is taking the signal out of the passband very quickly, so we have to track with the VFO continously.


In this file we can hear the transmission from SM7WSJ with calls


Here we copy RO RO RO from SM7WSJ

And, again Frank PE1NFE heard us, and made a new recording, see below.


In this recording Frank caught both stations first me sending calls, and then SM7WSJ sending calls, but slower speed.

In my opinon, the best recording of them all was made by Rune, SM5CUI. Good signal levels and brilliant doppler tracking, thanks Rune!


First we can hear me calling, then we hear RO's from SM7WSJ.

All files show huge doppler shift due to the fast moving object we are reflecting signals from.


To be continued.........


73 de Peter SM2CEW


Back to first page.