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Hi All,

Some pictures and description of my short range ground station antenna setup for the 2011/2012 OBC.

 

So essentially from the image above my antenna setup is:

  • 17dB 90 degree corner reflector antenna for WiFi down-link (video).
  • Digi 9xTend (900Mhz) on the top with a 6dB omni on the top (bi-directional link - autopilot)

The design philosophy for this antenna array is to provide the following:

  • Easy setup for LOS testing in the lead up to the OBC.
  • Flexible power supply.
  • Easy to transport.
  • Convert easily to mast mounted configuration as well as be well suited to design changes.

The game plan is that the final system will be mounted on a 4 meter mast attached to a car.  I wanted to integrate as much of the Tx/Rx hardware onto the antenna itself to keep antenna cabling lengths down (minimise the loss).

(above) This is the back of the corner reflector antenna it is home to:

  • A modified router running DD-WRT.
  • A battery (11.1 Lipo but this could be any power source in the range 8-42V).
  • Voltage indicator.
  • DC-DC voltage converter.

QUIZ!!! There is something wrong with the picture above... can you spot what it is?

 

Close of up of the router, the only modifications done to it was to replace the antenna with some RG58 (coming out the bottom) so it can be connected to the corner reflector. This particular router is running DD-WRT which is open source and allows you to configure almost all of the parameters of your router including Tx power.

 

N type plug that connects to the router to the corner reflector.

 

This is the DC-DC converter, it is just a COTS product from Sparkfun (LMZ14203). I selected this converter as it will allow me to run the system off portable power sources (batteries) that don't maintain a constant voltage. 

 

Okay so this box houses the Digi 9Xtend, the insides of this box are covered in a previous post here so have a look. It is mounted at the top of the mast to give a vertical separation of 80cm from the WiFi antenna which is roughly double what would be required.

 

Side on view, the mast is set on a slight angle so that the bulk of its weight appears over the center of gravity.

 

Antenna can be folded up for transport.

System diagram.

 

Overall I believe this configuration will give me the best compromise between performance/usability/scalability. If you have and comments or questions just shoot me an email via the contact page.


Tagged in: WiFi , USB , station , reflector , OBC , LMZ14203 , ground , Digi , DD-WRT , corner , CAT5 , Antenna , 9xTend , 900Mhz , 2.4Ghz
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