Portsdown 4 ISS Tracker

The Portsdown 4 ISS Tracker is designed to control an az/el rotator to track the ISS during a HamTV transmission. Initial testing has been on a G5500 rotator using the g5500pi controller (https://www.clearskyinstitute.com/ham/G5500/) connected to the rotator; however, other rotator controllers supported by HamLib rotctl may be compatible.

Portsdown Implementation

To access the rotator menu, go to M3, ISS HamTV RX Merger, ISS Tracker Set-up.

Before use, the Controller needs to be configured. Set either "Controller G5500pi" (the default) or "Controller HamLib".

If using the G5500pi controller, select "Set-up Controller" and enter the IP address and port of your controller in the format 192.168.2.140:8008. You may find it useful to allocate a fixed IP address in your network router for the controller.

If using the HamLib controller, select "Set-up Controller" and enter the HamLib device address. This is typically in the format /dev/ttyUSB2. Next enter the model number (the number in the first column of the table below), and the baud rate (typically 9600).

You should also enter the desired park position for your dish; the controller will move the dish to this position at the end of every pass. Select "Set Park Position" and enter the azimuth and elevation.

The configuration settings are stored for future use.

Now select "Track ISS". You should see the demanded position for the ISS displayed above the buttons, and the dish will move to track the position if it is more than 5 degrees above the horizon. Selecting "Track Moon", or "Track Sun" will also display the demanded position, and the dish will track if above 5 degrees.

Details

Selecting "Track Moon", "Track ISS" or "Track Sun" will always display the current position of the object in the sky. When "Stop" or "Park" are selected, the display of Demanded Position may not be valid. If using the g5500pi controller, the actual position of the dish is also displayed when "Track Moon", "Track ISS" or "Track Sun" is selected. It is hoped to extend this capability to HamLib controllers in the future.

Flip Mode

The controller always assumes that the rotator has an end-stop at North. To cater for ISS passes that are North of the dish location, and to better cater for overhead passes, 4 Flip Modes are available. The Flip mode button cycles between these 4 modes:

• Flip Mode Disabled. In this mode the maximum demanded rotator elevation will be 90 degrees. On ISS passes North of the dish location, some tracking time will be lost just after apogee as the rotator travels nearly 360 degrees to get to the other side of the North end-stop. Note that this mode is the only mode comaptible with rotators that cannot achieve more than 90 degrees elevation.

• Flip Mode Auto. This mode is a placeholder for a future capability to enable unnattended auto-selection of Flip Modes. Currently it has the same function as "Flip Mode Forced" below.

• Flip Mode Forced. In this mode, the azimuth is set to (demanded azimuth =/- 180 degrees) and the elevation is set to (180 - the demanded elevation). The effect of this is that the dish tracks the ISS "upside down" (beware waterproofing!) and the rotator end-stop is "moved" to South enabling continuous tracking of ISS passes North of the dish location.

• Flip Mode Half-flip. This mode is designed to cope with overhead, or near-overhead, passes where the ISS is within the dish beamwidth at apogee. Normally, such passes would need the azimuth rotator to transit 180 degrees after the ISS passed apogee, resulting in the loss of several seconds of tracking after the apogee as the demanded elevation decreased but the rotator was transiting through South while the ISS was in the East. In this mode, the tracking is normal until the ISS reaches an elevation of 80 degrees. Then the azimuth is frozen while the elevation still tracks to apogee; at apogee, the elevation enters flip mode, meaning that it continues to track the ISS through the overhead. Once the ISS descends through 80 degrees again, the azimuth control is unfrozen, but in flip mode, allowing continued tracking to the horizon.

The desired flip mode must currently be selected before the pass. It is hoped to automate this in a future update.

Supported HamLib Rotator Controllers

Portsdown 4 uses an early version of HamLib (rotctl(d), Hamlib 3.3) that supports the following controllers:

Rot #  Mfg                    Model                   Version         Status
    1  Hamlib                 Dummy                   0.2             Beta
    2  Hamlib                 NET rotctl              0.3             Beta
  201  Hamlib                 EasycommI               0.4             Beta
  202  Hamlib                 EasycommII              0.4             Beta
  204  Hamlib                 EasycommIII             0.4             Alpha
  301  XQ2FOD                 Fodtrack                0.2             Stable
  401  Idiom Press            Rotor-EZ                2010-02-14      Beta
  402  Idiom Press            RotorCard               2010-02-14      Untested
  403  Hy-Gain                DCU-1/DCU-1X            2010-08-23      Untested
  404  DF9GR                  ERC                     2010-08-23b     Alpha
  405  Green Heron            RT-21                   2014-09-14      Alpha
  501  SARtek                 SARtek-1                0.2             Untested
  601  Yaesu                  GS-232A                 0.3             Beta
  602  Yaesu/Kenpro           GS-232                  0.1             Beta
  603  Yaesu                  GS-232B                 0.2             Beta
  604  F1TE                   GS232/F1TE Tracker      0.1             Beta
  701  WA6UFQ                 PcRotor                 0.1             Untested
  801  Heathkit               HD 1780 Intellirotor    0.1             Beta
  901  SPID                   Rot2Prog                1.0             Stable
  902  SPID                   Rot1Prog                1.0             Stable
  903  SPID                   MD-01/02 (ROT2 mode)    1.0             Stable
 1001  M2                     RC2800                  0.1.1           Beta
 1101  EA4TX                  ARS RCI AZ&EL           0.1             Beta
 1102  EA4TX                  ARS RCI AZ              0.1             Beta
 1201  AMSAT                  IF-100                  0.1             Untested
 1301  LA7LKA                 ts7400                  0.1             Beta
 1401  Celestron              NexStar                 0.1             Untested
 1501  DG9OAA                 Ether6 (via ethernet)   0.1             Beta
 1601  CNCTRK                 CNCTRK                  0.1             Untested
 1701  Prosistel              Prosistel D             0.3             Beta
 1801  Meade                  LX200                   0.1             Alpha