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
Open Firmware
- to be advised
References
Link Budget
The link budget is the total gains and losses of a radio link.
For an OLPC XO using an access point, this is the sum of:
- for the access point:
- the transmit power,
- the loss in the transmission line (the coax and connectors between the transmitter to the antenna, normally very short),
- the gain of the antenna,
- for the environment:
- the loss due to distance,
- the loss due to obstructions,
- the loss due to noise, (from other radio transmitters),
- for the laptop:
- the gain of the antenna,
- the loss in the transmission line (the coax and connectors between the antenna to the receiver),
- the sensitivity of the receiver.
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 and connectors between the transmitter to the antenna),
- the gain of the antenna,
- for the environment:
- the loss due to distance,
- the loss due to obstructions,
- the loss due to noise, (from other radio transmitters),
- for the second laptop:
- the gain of the antenna,
- the loss in the transmission line (the coax and connectors between the antenna to the receiver),
- the sensitivity of the receiver.
See
