Station location: Kingston SE South. Australia – PF93VD
Operator: Tony Hutchison, VK5ZAI
VK5ZAI is an ARISS VHF-UHF telebridge station as well as a HamTV ground station.
Telebridge VHF-UHF system
- 10 turn helix 2m antenna
- crossed Yagi 20 + 20 70cm antenna
- VHF and UHF antennas are both about 5.5m long
- The reflector measures 4m x 2m
- The antennas are powered by 2 windscreen wiper motors
- Preamplifiers installed near the antennas
HamTV S-band system
- 1.2meter dish with a patch antenna on a DEM (Down East Microwave) preamp.
- MiniTiouner receiver
This is the AZ department.
The main drive was a final drive from a 70hp wrecked Case tractor.
Just behind the vertical shaft you can see the pinion that goes onto a 50:1 gearbox, This is spring loaded onto the crown wheel to avoid backlash. It is driven by a windscreen wiper motor.
To the left of the main shaft you can see a small alloy box which houses the digital encoder for the AZ feedback to the computer This is driven by a chain from underneath (not visable).
Tony made up a disc calibrated in degrees to fit on the main shaft. This is invaluable to get the AZ tracking correct. The main vertical shaft is 2″ to fit the main gear but just at the top of the photo you can see it goes onto a 5″ shaft for strength.
This is the EL. enclosure,
Starting from the left is the drive assembly. Motor and chain reduction drives are clearly visible.
Moving to the right and a little below the motor is the switching relay to change the polarity of the 70 cm Yagi.
The two alloy boxes in centre cotain the 70 cm and 2m pre-amps and switching relays.
On the right working down is the chain drive on the elevation shaft driving a digital encoder that feeds back the position of the shaft to the control computer. Below this is the Kuhne down-converted. Below this again, coupled into the co-ax feed, is a small box which taps of the 12 volts for the Kuhne and feeds the DEM low noise pre-amp on the dish.