This solution is becoming more popular. High-end bridges were first introduced for marine applications in about 2005. For a couple of years, these solutions cost upwards of USD 2000, essentially limiting them to the super yachts. By now they have come down in price significantly. See Ubiquiti solutions on data-alliance.net
Note: See Ubiquiti Picostation 2 HP: $90, has transmit power of 800mW, is very small, and has the RP-SMA fitting that allows antennae to be switched. In addition, it can be take 5-24V input power. It also has well developed software.
1) These units have fairly powerful and sensitive transceivers (400mW).
2) Different antennas can be attached and used as the situation calls for
3) The antennas are close to the transceiver
4) These are somewhat modular systems where transceiver cards, and antennas can be upgraded over time. (To upgrade the cards one needs to be fairly technically competent).
5) Bridges can often double as Access Points, meaning that multiple PCs can share the same connection to the shore.
6) Most of these units are weatherproof.
1) Antenna positioning: Whilst these systems can accommodate directional antenna(s), one still has to get to the antenna to aim it. A permanent installation high up a pole may make it difficult to aim the antenna…
2) Power: These systems can draw 3A of power and/or require 110V, 48V, or 24V. Read the manuals to verify the input power requirements. Ideally one powers them directly off the onboard 12V system.
3) Ease of use: Configuring and maintaining these systems requires extra skills and attention to detail that go beyond what most cruisers have. We know of two boats that threw them out because they were too cumbersome to administer.
There are cheap off the shelf WIFI Bridges (e.g. Linksys WET54G). The transceivers contained within them have lower power and sensitivity than is optimal on board use. In addition their software isn’t optimized for on board use. Stay away from them!
Bridges have come down in price and are becoming more attractive. However, we think a bridge is overkill for most users. In addition, a permanent install seems (somewhat) at odds with a directional antenna, which in our experience is so important for increased range. We had a system like this on Bravado. We found it performed worse than the “Bravado solution” described below. Later we met with a super yacht that had a top of the line Syrens system. Again, we could see substantially more Access Points than they could. If you really want a permanently installed system, a bridge indeed is the way to go. However, using just an omni-directional antenna means a significant performance hit. Other people also report that a modular USB solution yields better results.