April 30th, 2013

The doppler shift was the problem to be solved for performing further steps in ISS bounce. There are two practical strategies: If every station will compensate its own doppler component, so even random QSOs would be possible. The other solution is, when the whole compensation will be done by one of the stations. That would open ISS bounce to stations that are able to do antenna tracking on the ISS, but not to compensate the doppler. In this case it is required to arrange skeds, because the compensating station is required to know the coordinates of the other one.

Basing on DC9ZPs E-Book I extended the software, I use for station control, by satellite tracking. That opens the possibility to calculate the relative speed and the resulting doppler shift of the ISS pertaining to given locations and given frequencies.

Above diagrams show the elevation with the according doppler components on 1296 MHz for a window between DJ5AR, JN49CV in Mainz (green) and EI8HH, IO53HN near Galway (blue). If the full doppler compensation will be done by one of the stations, the red line with a total span of 120 kHz will be relevant. The window in this example would open for about five to six minutes.