J.F.Drew © 2000-2013

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VK5DJ

Satellite system at VK5DJ

My satellite system effectively tracks satellites using the beam rotator project in external control mode.


I use Orbitron to calculate the satellite position and my program Remote (Self extracting) or here ( ZIP file) to communicate between the computer and the shack unit.


To get the best out of the system use the latest shack software version greater than Version 8.1. I use a potentiometer for azimuth and a SCA61T inclinometer for elevation.

Left: The old CDE rotator that was modified to remove the earth connection on the pot to overcome serious noise problems. Note the rubber universal joint to overcome any alignment problems. Thanks to Chris VK5MC who found it in his machinery shed.


Right: is the circuit board of the SCA61T inclinometer chip. See below for details on how this may best be mounted. The photo shows it in a test jig.

Top right: The completed antenna system for 2M/70cm satellites. Both yagis are based on the DL6WU design produced by my Yagi Calculator program. The 70cm antenna is a 16 element one with an estimated gain of 14dBd while the 8 element 2M yagi has an estimated gain of 10.4dBd. The screwjack provides elevation movement of about 100 degrees. The aluminium box at the top covers the SAC61T inclinometer encoder system described elsewhere on my site. Readout is more than adequate for satellite work and the antennas in use. The photo makes it look as if the antennas are not aligned, it's an optical illusion, they are.


Thank you Stan LZ2STO for the 18 inch screwjack. It provided the incentive for me to finish my satellite system. Thanks too to Seb DG5CST for the inclinometer chip.

  1.  Rasping noise from the elevation encoder radiated into the satellite antennas from cable. Fix was to put two "clamp on" ferrite suppressors as close as possible to the elevation box. In hindsight I should have put the elevation encoder system in a metal box as I still have some weak spots coming out of the 10MHz oscillator - fortunately these are not where I listen.
  2. Noise from the screwjack motor. Not bad but it's there, so will put some ferrites on the power lead to the screwjack as close to the screwjack as possible. It may need some caps as well.
  3. AC ripple on the voltage coming back from the CDE44 rotator pot. See elsewhere for the fix which involved isolating the wiper from earth.
  4. RF got into the A/D converter for azimuth when running 200W on HF. I installed a filter made from a ferrite ring and four bypass caps. 22uF and a .001 in parallel on the input of the choke and similar on the output of the choke. The filter assembly was placed inside the beam rotator box close to the DB9 socket.
  5. Discovered the hysteresis wasn't working as I planned. This is fixed from Version 8.11
  6. Discovered that better adjustment of the AZ and EL spread was required other than 10 deg increments. Version 8.20 of the shack software now supports any spread from 20.0 deg to a very large number.

Left: the rotator corner with my controller in the top right hand corner. I’ve recently replaced it with the 4 line version.


Right: The SCA61T elevation encoder is in a plastic box, in turn inside a weatherproof aluminium container.

Problems encountered in installation

Left:The operating position showing the TS790A for 2M/70cm. Just showing to the upper left of mike is relay switching and LED display of antenna in use.


Right: The power supply for relays and preamps and old CDE 44 control box for the rotator live out in the shed.