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When complete, our spectrum mapping setup will consist of

  • One 5 GHz Ubiquiti Bullet M5 - For raw spectral scanning
  • One 5 GHz Ubiquiti Bullet 5 HP (or Bullet M5) - For wifi scanning
  • One 2.4 GHz Ubiquiti Bullet M2 - For raw spectral scanning
  • One 2.4 GHz Ubiquiti Bullet 2 HP (or Bullet M5) - For wifi scanning
  • High-gain omni-directional antennas for all Bullets
  • One Elonics E4000 USB adapter (compatible with RTL-SDR)
  • One GPS unit with 3.3v serial interface
  • One XO-1 Laptop
  • One USB ethernet adapter for laptop
  • One passive five port ethernet hub with PoE
  • One 12 volt Li-Ion battery
  • One charger for Li-Ion battery

The idea is that this can all be mounted on a bike (petty cab?) or car, and driven around the city to create maps of which parts of the spectrum are being used for wifi, how much, and how much total signal is present on different parts of the spectrum.

Contents

What we have so far

Spectral and GPS prototype

A 5 GHz Bullet M5 with a patched OpenWRT that does spectral scanning, hooked up to a ublox neo 6m gps module using the 3.3 volt serial pins on the Bullet. Only the ground, 3.3 volt power and receive (on bullet) pins are connected. Transmit from the bullet is not connected because the Bullet spews a bunch of output that we haven't figured out how to completely eliminate (how can redboot serial output be disabled?) and may confuse the GPS module, and because the GPS module works just fine without every needing any commands sent to it. It simply transmits all of the info it has on current satellites and its position every second.

XO-1 laptop

We have an XO-1 laptop running Debian. See this guide.

Battery system

We'll be using a battery controller from an old Macbook G4 battery, with a new set of Li-Ion cells.

The charger will be a whatever high-powered 12 volt power supply we have lying around that we'll modify to output the slightly-higher-than-12-volts that the Macbook G4 battery controller expects. Instructions to follow.