2009-10-12T02:15:00.000-07:00

Common Problems

In locations where shore-based Wi-Fi signals are strong, using them for Internet access on a boat is comparable to using Wi-Fi hotspots on land. However, the marine environment tends to exacerbate general Wi-Fi problems and create other problems of its own:

Boat hulls and sailboat masts can block radio signals, reducing range.
Movement of other boats can cause interruptions of Wi-Fi connections.
Location of a Wi-Fi antenna in a cabin below deck can further reduce range.
It may be difficult to get close enough to the Wi-Fi access point for sufficient signal, especially when anchored.
Boat movement can result in aiming problems with highly directional antennas (even when tied up).
Moisture in the marine environment can result in electronic failures.

Improving Wi-Fi

Higher Power

American Alligator

While it may seem that higher power Wi-Fi might help to improve your range, that's not necessarily true, since higher power only helps on transmit, not receive. Thus it's only likely to help if the other end of your connection is using higher power as well, which is often not the case. In other words, what you may well wind up with is an alligator, big mouth but small ears. Also, unnecessarily high transmit power will tend to increase your interference with other Wi-Fi users, making you a bad neighbor. It's usually much better to just improve your antenna, which helps both transmit and receive.

Better Antenna

Outdoor wireless access point with high-gain omnidirectional antenna.

Usually the best way to improve range is to use a better antenna (or reflector with a standard antenna), which helps both transmit and receive.

Better antennas work by being directional:

concentrating radio energy/sensitivity to/from the desired direction instead of wasting it in pointless directions, and
reducing interference from other radio sources not in the desired direction (path).

The improvement in antenna performance is referred to as gain, where a higher number indicates the amount of performance improvement expressed in dBi. It takes an increase of 6 dBi to double range; e.g., as compared to a typical 2 dBi antenna, an 8 dBi antenna has double the range.

However, a highly directional antenna can be problematic on a boat, since it must be kept aimed accurately at the remote end of the connection, which can be difficult on a boat floating in the water (even when tied up). The width (angle) of the directional pattern (both vertically and horizontally) can be used to see how accurately the antenna must be aimed.

The simplest and easiest improvement is to use a higher-gain omnidirectional antenna (4-8 dBi), thereby avoiding the need to aim the antenna horizontally (point it at the shore-based wireless access point). Such an antenna works by concentrating energy/sensitivity in the horizontal direction that would otherwise be wasted vertically (up and down). Beyond about 8 dBi the vertical beam angle becomes so narrow that vertical aiming can be problematic on a boat:

Omnidirectional
Antenna Gain

Example of
Vertical Beam Angle

4 dBi

6 dBi

8 dBi

10 dBi

12 dBi

50°

28°

15°

11°

8°

Antenna Location

Higher antenna locations tend to have less interference (e.g., from other boats) than lower locations, so in general it's a good idea to locate the antenna as high as is practical. On a sailboat, the ideal location is at the top of the mast.

Since signal loss in the cable between the radio unit and the antenna increases rapidly with the length of the cable, it's better to locate the radio unit next to the antenna, and use lossless cable to support the radio unit, either USB or Ethernet, both of which have advantages and disadvantages (as noted below).

Automatic Tracking

There are products than can be used to keep a directional antenna aimed at an access point as a boat swings or drifts with precision of better than one degree (e.g., Track-It-TV). However, they are relatively expensive, and they only track in the horizontal plane, so it's important that the vertical beam width take into account rolling and pitching of the boat. Usually a vertical beam angle of 10 degrees or so is adequate for all but the roughest conditions, but even beam angles of 20 degrees or more can still result in substantial improvement in gain over an omnidirectional antenna.

Temporary Setup

Setup as needed, packed away when not in use. Ideally the radio unit and antenna are located together as high as possible (e.g., outside on the top of the cabin), usually connected by cable:

USB

Hawking HWU8DD Hi-Gain USB Wireless-G Dish Adapter

Advantages:

Simplicity
Lower cost
Power over USB cable standard

Typical USB setup:

Hawking HWU8DD Hi-Gain USB Wireless-G Dish Adapter
(8 dBi, must be aimed)

Caveat: Maximum length of a USB cable is 5 meters (about 16 feet), although that distance can be multiplied by means of one or more USB active extension cable(s), effectively a standard USB cable married to a one-port USB hub (e.g., StarTech USB 2.0 Active Extension Cable USB2FAAEXT15).

Note: USB Internet connection can be shared by means of Internet Connection Sharing and a separate network (e.g., Ethernet).

Ethernet

Buffalo Wireless-G High Power Ethernet Converter WLI-TX4-G54HP

Advantages:

Long cable (up to 100 meters)
No USB driver needed (universal)
Support multiple clients with a hub or switch

Caveat: Not all Wireless Ethernet [client] Bridges support multiple clients. Check manufacturer specs and/or Wi-Fi Wireless Ethernet Bridges.

Typical Ethernet setup:

Buffalo Wireless-G High Power Ethernet Converter WLI-TX4-G54HP
Buffalo 6 dBi Detachable High Gain Directional Antenna WLE-AT-DACB (if needed, must be aimed)
[1][CA World WiFi Client Setup]
http://www.ubnt.com Ubiquity Networks Nanostation2 and Bullet2 (or Bullet2HP). Include a router so eliminates the problem of IP addressing both the client and the internet. Prices unbeatable. Include POE from 12V. Range of many miles.
CA World WiFi

Power: Separate power cable, or it may be possible to use Power over Ethernet. Check manufacturer specs. Lightning/Surge Protection: This is a must in a Marine Environment. It will protect your investment in any wifi equipment from this natural occurance.

Wi-Fi on a Boat