Parabolic wifi dish

These dishes, left on peoples houses from a now-defunct satellite TV provider, are ideal for wireless LAN links. The gadget on the arm replaces the original LNB and consists of a simple biquad (etched onto a PCB) enclosed in a weatherproof box. This in turn is mounted on a galvanised steel reflector to further enhance the signal. This configuration gives better than 20 dBi signal gain, but it still pays to minimise the coax cable run - that's why the AP is mounted nearby in the little waterproof box you can see (without its lid).

WAP in a box

Close-up of the Minitar MNWAPB mounted in its little weatherproof case. The 'extra' exposed wires are the retrofitted Power Over Ethernet (POE) connection. To save running mains power up the tower, the power supply for the AP is located remotely and the 12V DC run through a spare pair in the Cat5e cable. The whole setup is mounted on a water tower adjacent to the main homestead - very convenient and it saved having to construct a tower!

Battery backup

This is the other end of the Cat5e from the AP on the tower, mounted in a weatherproof gear cabinet in the outside wall of the homestead. The cabinet is connected to mains power and has a single LAN outlet. As you can see, the POE is connected directly to a 12V sealed lead acid battery, which in turn is kept topped up by an intelligent trickle charger. As the AP is internally regulated and only requires 12V DC input, this was cheaper, more logical and more efficient than just running the APs plugpack on a little UPS. The charger has enough overhead to simultaneously run the AP and recharge the 7.0Ah battery after a blackout before automatically switching back to float charge. The longest outage we have seen since this was installed was about 8 hours, and the AP was still up at the end of it. The AP doesn't draw much current (its plugpack was only 500mA), and I've already found a good network switch (a Linksys SD-205) which also runs on 12V with minimal current draw. This switch will be installed on the battery if we need any more devices in the cabinet connected to the network.

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