Ask the Wi-Fi Guru About Long-Range Bridges - Page 2

By Aaron Weiss

March 17, 2011

By analyzing the traffic in the passive mode, the client can infer a variety of information about the wireless network, including its SSID. This method can also be used for malicious purposes, such as cracking a WEP password or sniffing unencrypted traffic from clients. Often, using passive mode requires special device drivers for the wireless adapter.

All of this is a long way of saying that in passive mode, the AP should never receive the MAC address of a passive client unless and until that client switches to active mode and makes a probe request or associates with the AP.

How do I make a Wi-Fi bridge with a two-mile range?

Q:I want to make a bridge with a 2 mile range. C Crane makes a kit. In theory could I add a grid antenna to my Linksys host and client routers? Do I need a power injector as the C Crane kit? Does the power injector power the antenna or is it powering their bridge? I am just a little fuzzy as to whether the power injector is necessary. - Carson

A: The bridge kit uses the power injector to feed the bridge units, which are essentially like miniature routers packed into a small housing. Power injection delivers low power over an Ethernet cable, so that only one physical cable is necessary to connect a network device like these bridge units. Often, power injection is used for situations where the network device will be installed in an out-of-the-way location where a traditional power source is not easily accessible.

If you are building your own bridge using conventional routers, then they will have their own AC power. No further power injection is necessary.

That said, you will need to be using a router that can accept an external antenna. Some do and some don't. Routers which do accept an external antenna typically use one of several connection types, the most common being TNC and SMA, or the RP- (reverse polarity) versions of these.

When you choose an external grid antenna, it may not have a connector that is compatible with your router. Some vendors will let you specify a connector type, so be sure to look up your specific router model in advance. There are also adapters available to connect from one type to another. Be aware, though, the adding adapters and cable length to your external antenna will decrease signal strength.

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