AGAF DATV tests at HAM RADIO 2008
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On Friday June 27th DATV specialist Willi DC5QC started a test transmission on 70cm in QPSK 
mode from Wasserburg at Lake Constance to Pfaender mountain above Bregenz in Austria. Our 
23cm yagi antenna on the roof of hall A1 in the Friedrichshafen fairground had been pointed 
to Pfaender mountain in order to receive fine panorama video in QPSK mode from DL0DTV/OE at
"Hotel Schoenblick", but also repeated signals from portable 70cm-DATV stations. Willi´s 
video arrived in decent quality (10 dB SNR without preamp) at the Friedrichshafen fairground, 
after the Wuppertal students in the hotel (from DJ8DW´s developer staff) had reduced the 
data-rate of their MPEG encoder. Earlier there were short blackouts caused by strong inband 
signals and some artifacts with fast movement in their camera video - the modulator had been 
overturned by too much video data coming in.

After lunch time another highlight took place outside the hall: a planned wheather balloon 
launch by OM from DARC chapter P56 and AATIS. As payload a 2m and a 70cm TX together with 
digital cameras and some electronics went up into the blue sky, sending for instance a 
Slow-Scan-TV signal to earth at times. The combined Packet-Radio data-, speech synthesizer- 
(announcing balloon hight and position) and SSTV signal (one after the other) was received 
on 145,200 MHz at the Pfaender mountain without interference. So the Wuppertal students at 
the 23cm DATV TX location put the received audio signal onto their second audio channel 
like it was agreed before between Uwe DJ8DW and the balloon team. At the AGAF stand in 
Friedrichshafen this audio was picked from the digital satellite TV receiver and again 
modulated a small 2m FM transmitter which carried it to the AATIS stand at the other end of 
the hall. There the balloon data was evaluated and shown on a big video screen. During it´s 
flight of two and a half hours the balloon reached 29313m ASL and descended at JN57DK on the 
austrian alps.

On Saturday morning Uwe DJ8DW and Willi DC5QC made a joint DATV test trip to the aerea west 
of Friedrichshafen in order to try longer distances with their 70cm QPSK signal (14 Watt into 
an 11-El.-Yagi). From a high-situated parking place near Hagnau the first decent live video 
(and sound) arrived at the AGAF stand after repeating at the Pfaender mountain. Sorrily the 
mobilists were not able to receive the 23cm "repeater" signal from Hotel Schoenblick because 
of some trees in the line of sight. This succeeded after changing to another parking place 
near Meersburg with unobstructed line of sight over more than 40 km distance. Another proof 
that our 70cm band is an indisputable treasure! 

Klaus, DL4KCK