Wi-Fi for Sailors
The term Wi-Fi gets bandied about plenty these days. After all, you probably use it to obtain high-speed Internet access at work, in airports and hotels, or at home, and youve probably used it on your boat, likely with varying degrees of success. Built-in Wi-Fi hardware in laptops, or PC Wi-Fi-card adapters (802.11 cards), such as those from Linksys, work fine if youre close to a hotspot (geek speak for a wireless Internet connection), but gettingand keepinga signal isnt always easy at a marina. And using Wi-Fi on a mooring, at anchor, or while sailing is often problematic. The problem is that the integrated systems in a laptop or in an 802.11 PC Wi-Fi adapter card arent powerful enough to get and maintain a good Internet connection more than 300 feet away from a hotspot.
Unless youre a computer geek, you probably use Wi-Fi without knowing much about what it is or how it functions. While the underlying technology can get confusing when looked at on a granular level, it neednt be intimidating.
Theres a whole alphabet soup of Wi-Fi terminology, much of which you dont really need to understand, but some knowledge of it is helpful when you start examining Wi-Fi systems for your boat. Lets start with “Wi-Fi” itself. Wi-Fi stands for wireless fidelity and is a trademark of the Wi-Fi Alliance, a nonprofit organization working to ensure conformity to the IEEE 802.11b standard. Originally known as the Institute of Electrical and Electronics Engineers (IEEE), the Alliance is a professional organization covering a wide scope of scientific disciplines. IEEEs 802.11b was the first standard for Wi-Fi. It basically denotes the transfer of data to and from a computer over a radio frequency of 2.4GHz and operates quite like a VHF radio. While both VHF and Wi-Fi use radio waves, Wi-Fi operates at a much higher frequency that can accommodate much more data.
In the sort of wisdom known only to computer geeks, the standard flipped alphabetically backwards in its next evolution to 802.11a, which also operated on a frequency of 2.4GHz, and then skipped ahead in the alphabet to 802.11g on 2.4GHz. The important thing about all this is that 802.11b is slow with data transfer rates of only 11 megabits per second (Mbps). Its still in use, whereas 802.11a has gone by the wayside. What you want is equipment that coheres to the 802.11g standard because youll get a theoretical data-transfer rate as fast as 54 Mbps. Obviously, when it comes to the Internet, you want fast data transfers, which is why the 802.11g standard is the most common in todays Wi-Fi applications. Most Wi-Fi products for your boat will accommodate both 802.11b and 802.11g to achieve the widest possible access.
An above-deck antenna designed to withstand the marine environment is an important component of most onboard Wi-Fi systems. Youll see antennas designated as 2dBi, 8dBi, 10dBi, and higher; dB is an abbreviation of decibel and dBi describes antenna gain. Higher-gain antennas enhance signal reception and deliver better performance than lower-gain antennas. Most Wi-Fi systems for your boat incorporate a high-gain, omni-directional antenna, which means that it handles signals from all directions equally well.
You want an omni if youre out and about on your boat. However, if you only want to use your Wi-Fi system at your slip, where the boats position remains constant, a directional antenna aimed at the marinas hotspot is an excellent option. Generally speaking, it will deliver a better signal than an omni with the same gain, but only from one compass-point direction.
Transmission power is another key factor. Not every system delivers the same power punch, nor do all systems have an antenna with the highest-possible gain, and therefore ranges vary widely. Look for transmitters with as much power as you can afford, and get a higher-gain omni antenna for the most flexibility. These two components will greatly influence the way the overall system performs.
Some manufacturers claim their systems have a range of up to 12 miles, but always with a disclaimer that every situation is different and subject to factors that can degrade range, such as signal loss through interference and attenuation. Like your VHF radio, Wi-Fi works on line-of-sight, which is why you can happily use your laptop with installed Wi-Fi hardware in the cockpit at a marina (sometimes), and why you often lose the signal when you take the laptop below. Maintaining line-of-sight and reducing interference from buildings and other objects is critical. The typical range for most systems is from one to five miles, and its often greater in permanent and custom installations, depending on the system you select.
Power is expressed in milliwatts (mW). Generally speaking, the more transmit power, the better. For example, some Wi-Fi hardware built into a laptop is as low as 30mW, whereas the transmit power on the Wi-Fi systems available for use on your boat can be as high as 1,000mW. Typically, youll find 400mW is the most common.