new GMSK-Tests on 434 MHz in Germany
------------------------------------
In October 2005 several prototype boards of the GMSK-DATV receiver developed by 
the group around Uwe, DJ8DW, at University of Wuppertal were ready. Willy, DC5QC, 
and Rudolf, DJ3DY, helped to fit them with components and to proof test them at 
the "Chair of Communications Technologies". 

In the end we were able to establish a contact between our home stations with 
two sets, although the route from Haltern (DC5QC) to Bochum (DJ3DY) is nearly 
34 km without line of sight.

Willy`s equipment: DATV encoder and 434 MHz exciter by DJ8DW, PA 80 W by Microwave, 
antenna 19 el. yagi horiz. 20 m above ground. The eye diagrams were barely open, 
but the improved receiver software decoded sound and vision in good quality in 
spite of severe ISM interference (LPD band around 434 MHz). Some dropouts were 
caused by GMSK type signals appearing in different time frames.

The next day also DJ3DY was ready to transmit, after Willy had repaired parasitic 
oscillations in a driver amplifier of DJ3DY, and the retransmitted video from DC5QC 
appeared on the screen in Rudolf`s shack.

Station DJ3DY: DATV encoder and 434 MHz exciter by DJ8DW, driver module M57745 with 
3 W, PA 80 W by Motorola, antenna 11 el. yagi 15 m above ground. A week later 
another test was successfully performed between DJ3DY and Peter, DF4EA, in Essen 
about 12 km away.

This link was stable all the time, only the vertical omnidirectional RX antenna 
tested by fault (hi) generated some dropouts caused by ISM signals. Then on 
31.10.2005 Peter transmitted to DC5QC over 38 km distance in proper quality with 
some ISM dropouts. Willi returned the video on ATV repeater DB0CD, so Peter was able 
to check his own signal.

Station DF4EA: DATV encoder and 434 MHz exciter by DJ8DW, PA 80 W by SSB-Elektronik, 
antenna 18 el. yagi. Now we are hoping to get some more receiver sets from Wuppertal 
after completing the software design.

Rudolf Pfeiffer, DJ3DY
1.11.2005