Sunday, 30 March 2008

Internet Afloat

Many people have asked us for details of the wi-fi system we use to connect to the internet, in marinas and anchorages, so here they are. As you may know, the 2.4ghz wi-fi system is intended for relatively short range network communications, and the service can be quite unreliable if you're more than 30 metres from an antenna site. To make matters worse, our steel hull acts like a Faraday cage, effectively preventing us from using the system from down below.

In Singapore we found a product that solved these problems - a high power wi-fi transceiver that connects by USB cable to the PC. This allows us to put the transceiver and antenna outside the boat, for best performance. The unit is a Senao EUB-362EXT, with removable antenna. Read the technical details here. It comes with a small high gain antenna (see the brochure at the link abaove), and will usually provide much improved performance over the antenna's that are built into the screen housing of most modern laptop computers. For even better performance, we removed the supplied antenna and connected the transceiver box to a waterproof high gain antenna mounted permanently, high on the vessels railing. Note that the cable between the antenna and the transceiver should be kept as short as possible - do not use standard RG.58 coax, instead look for a coaxial cable with low loss at 2.4ghz. We used German manufactured Bedea RG223, purchased from Coastal Electronics in Singapore (details here).

With these elements in place we can usually connect at quite extreme distances - more than a kilometer is quite common. The optimal antenna gain seems to be about 8dbi, allowing for the rock and roll of the vessel in a sloppy anchorage. Other high gain antenna systems that must be "aimed" are less useful for us, as they lose the signal if the boat swings at anchor (which it always does ....). Waterproof external antennas are made by many manufacturers - ours is a CD.2408 made by RFI, and is about 300mm long. If you're in the area, all the necessary parts can be found at Sim Lim Square in Singapore. A most helpful supplier is Media Mart -see the card at left, or click here for complete purchase details in Singapore. External waterproof antenna can be purchased from R1 Trading Pte Ltd at Sim Lim Square.

I note that some folks have had difficulty with the installation of the Senao software - make sure you use the latest drivers, and make sure your internal wi-fi is disabled before installing the Senao product. If you use Windows Vista (you're bolder than we are), the drivers can be downloaded from the Senao Networks site here.

We have many friends in Asia and the USA using this system, and we recommend it highly. Where signal is available we enjoy solid 24x7 internet access, usually at quite low cost. The computer can stay in its permanent position adjacent to the chart table. Transmission speeds on the system are often good enough for high quality Skype calls, and we have seen one or two video calls succeed, though that is asking a bit much !

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