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Friday May 1st, 2015 the Ham Video transmitter on board the Columbus module of the International Space Station was powered on and started transmitting in “Blank Transmission” (BT) mode.
In this mode, the transmitter is operated without camera. The digital TV signal is fully formatted, but the content of the video is black and the content of the audio is at zero level. From a technical perspective, the BT signal is all that is needed for testing and fine tuning ground stations.
The European network of chained ground stations is presently nearly complete. Six ground stations span the continent in “X” formation. For each ascending pass over Europe, four stations provide about ten minutes of solid copy and the same is true for descending passes:
– Ascending passes: Lisbon (Portugal ==> Poitiers (France) ==> Casale Monferrato (North Italy ==> Kolo (Poland)
– Descending passes : Cork (Ireland) ==> Poitiers (France) ==> Casale Monferrato (North Italy ==> Matera (South Italy.
The chained ground stations are streaming the digital video to the BATC server (British Amateur Television Club). BATC set up a multiviewer page, accessible at: http://www.batc.tv/iss/
The page shows all six streams from the chained ground stations. Each view can be maximized to full screen and the audio of each stream can be set to level or muted.
Presently, active stations stream technical data provided by the software developed by Jean Pierre Courjaud F6DZP. Several data are most interesting to observe:
– the “constellations”, which visualize the QPSK (quaternary PSK) modulated signal
– the digital Signal/Noise ratio = MER (dB) (Modulation Error Ratio)
– the control LEDs that change from red to green on decoding the digital signal.
The Ham Video transmitter frequency is 2395MHz and the symbol rate is 2.0Ms/sec.
More information is available at: http://www.ariss-eu.org/
The Ham Video transmitter will stay on as long as on board operations permit. When the ground stations will be operating reliably, the Ham Video transmitter will be used to enhance ARISS school contacts. Uplink will remain VHF audio only. This operational mode is dubbed ARISS Ham TV.
Gaston Bertels – ON4WF