Antenna testing

How to test the OLPC XO antennas.

Why test them?

• they may have been damaged by impact, misuse, or electrostatic discharge,
• to classify laptops for repair,
• to verify a repair,
• to survey a site,
• to find parts of a site that have low coverage.

Linux, GNOME or Sugar

• connect to an access point,
• use Browse, Firefox or Epiphany to visit a web page,
• while transferring data, display the signal and noise values:

iwconfig eth0

References

Link Budget

The total gains and losses of a radio link.

For an OLPC XO using an access point, this is the sum of:

• the access point transmit power,
• the access point transmission line (the link from the transmitter to the antenna, normally very short),
• the access point antenna,
• the loss due to distance,
• the loss due to obstructions,
• the laptop antenna,
• the laptop transmission line (the coax from the antenna to the receiver),
• the laptop wireless card receiver sensitivity

For two OLPC XO using an adhoc network, the link budget is the sum of:

• for the first laptop:
  • the transmit power of the wireless card,
  • the loss in the transmission line (the coax from the transmitter to the antenna),
  • the gain of the antenna,
• for the environment:
  • the loss due to distance,
  • the loss due to obstructions,
• for the second laptop:
  • the gain of the antenna,
  • the loss in the transmission line (the coax from the antenna to the receiver),
  • the sensitivity of the receiver.

See

• http://en.wikipedia.org/wiki/Link_budget