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Wi-Fi on a Boat

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Making shore-based Wi-Fi Internet work well on a boat.

Tip: See also Wi-Fi (main article), Wi-Fi How To, Fast Fixes to Wi-Fi Problems, and Cellular on a Boat

Common Problems Edit

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 Edit

Higher Power Edit


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 Edit

Wireless ap outdoor

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:

Antenna Gain
Example of
Vertical Beam Angle

4 dBi
6 dBi
8 dBi
10 dBi
12 dBi

Omni Antenna Patterns

There is a fair amount of discussion here about beam width and why a boat must have an omni antenna with about 8 dBi or less gain. Let us do a practical test of this. Take your hand bearing compass out and site a location about 1000 feet from your boat. Then slowly turn six degrees and look at that point. Now imagine that distance turned vertically and that is the beam with of an omni antenna with a beam with of 6 degrees at 1000 feet. Repeat this for a point 2000 feet away, then 3000 feet away, then 6000 feet away.

This test convinced me to experiment with high gain omni antennas from the practical perspective of a sailing boat. I am not disagreeing that at close proximity that a lower gain antenna is better. But as the distance increases the effective beam width increases. Years of actual experience aboard sailing boats confirms that higher dBi gain omni antennas work well on a boat at anchor as well as at a dock close to the shore side station.

Antenna Location Edit

Higher antenna locations tend to have less interference from obstructions (e.g., biminis, dodgers, booms, and other very close proximity boats) than lower locations since there are more obstructions on a boat closer to deck level, so in general, it's a good idea to locate the antenna as high as is practical. WiFi is line of sight, and the use of a medium gain antenna (4dBi-9dBi) will provide a fair amount of flexibility in accessing WiFi access points on shore regardless of the height of the antenna on the boat due to it's wide cone of transmission. Use of a higher gain antenna (12dBi - 15dBI) may cause you to have a need to adjust the height of your antenna based on the access point location since the cone of transmission is significantly smaller than on medium gain antennas. Height is important to get clear of nearby obstacles however mounting the antenna on a mast of a sailboat is typically unnecessary.

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 Edit

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.

There are hobby projects to build an auto-aiming directional antenna capable of staying locked into the best signal while a boat rotates around an anchor line.

Temporary Setup Edit

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 Edit

Hawking HWU8DD Hi-Gain USB Wireless-G Dish Adapter

Hawking HWU8DD Hi-Gain USB Wireless-G Dish Adapter


  • Plug and play (check manufacturer's specifications)
  • Low cost (desktop type devices).
  • Power provided by USB cable, directly from the computer so no additional cabling is required.
  • USB Devices are designed for portable applications with quick (i.e. boat moving from port to port) setup.
  • Can often be used onshore as well as on the boat.
  • Using a software based access point (ICS), you have the ability to connect multiple computers or devices that use only built in Wi-Fi (such as iPhones and iPads) with no additional hardware purchase.
  • Some products integrate directly into the operating system making their use as simple as built in WiFi adapters.


  • Maximum length of a passive 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).

    1 Watt USB Adapter with antenna

  • Requires software drivers to be installed before the WiFi unit can be used. (Check with manufacturer to assure compatibilty with your particular operating system as not all units will work on all operating systems.)
  • Potentially more complex connection sharing. USB Internet connection can be shared by means of Internet Connection Sharing (on both Windows and Mac OS's). If using Microsoft Windows 7, this has become trivial via "Virtual WiFi". Connection Sharing will require the sharing computer to be left on whenever connection sharing is needed, however, no additional hardware or electricity requirments are needed in order to allow multiple devices (i.e. iPhone, Blackberry, iPad, etc) to get online.
  • When running from a laptop battery, the power consumption of a high power Wi-Fi device will deplete the battery at a higher rate than if using the computer with no external devices attached (maximum USB port power is 500mA at 5v). The actual rate of power consumption by a USB device will be dependent on the device being used, so check manufacturer's specs for power draw.

Typical USB setup:

Ethernet Edit

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

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


  • Long cable (up to 300 feet or 100 meters) - masthead mounting becomes achievable.
  • No software drivers needed by computers. Firmware built into ethernet based devices control Wi-Fi access. This makes hotspot selection changes more flexible since any computer or device is capable of doing this via a browser. However, most interfaces of these devices were designed for network engineers so check manufacturer for information about usage.
  • Ability to create private networks using switches, hubs and wireless routers. Ability to connect multiple computers or computers that do not have Ethernet or USB connections and use only built in Wi-Fi (i.e. iPads, iPhones, Blackberry, other tablets).


  • Not all devices support multiple clients. Check manufacturer specs and/or Wi-Fi Wireless Ethernet Bridges. However, PC Connection Sharing (same as above with USB systems) can be used.

    Bitstorm's BAD BOY Xtreme

  • Client bridges, repeaters, and routers all require a source of external power. Devices require either a power cable or PoE (Power over Ethernet). Check manufacturer spec.
  • Depending on supplier, configuration and management can be more difficult for average

    Wi-Fi for Boats Omni antenna and Wireless Ethernet Router.

    computer users. Check supplier specs.

Typical Ethernet setup:

Hybrid Solutions Edit

There are a new set of solutions that are coming to the market that combine the benefits of both USB and Ethernet based systems into an extremely easy to use package and provide a full onboard network for your boat as well as give you long range connectivity to shore-side access points.


  • Single hardware and cable installation, no Ethernet or USB cables to use.
  • No software to install, connect 12V power and connect over WiFi.
  • One user interface to manage both local network and connection to remote access point.
  • Power supplied by standard 12V power cable. Typical draw is < 500ma.
  • Unlimited cable length, allows unlimited mounting possibilities.
  • Built in Access Point allows all devices to share the WiFi connection simultaneously.
  • Management of the device can be performed by any WiFi enabled device with a web browser (ie PC, Mac, iPhone, iPad, etc)


  • Depending on supplier, configuration and management can be more difficult for average computer users. Check supplier specs

Typical Hybrid setup:

  • The Wirie AP - Long Distance, Easy to Use, Simple Installation, Affordable - Marine Grade, for Boats and RVs. Built in access point, 12V power source.

Lightning/Surge Protection: This may protect your investment although lightning suppressors may cost as much as the Wi-Fi equipment itself.

Permanent Installation Edit

[[Image:CA World WiFi 250mW Outdoor WiFi transmitter -

WL24005 Outdoor AP/Client

.jpg|thumb|CA World WiFi WL24005]]

Any permanent mount solution mounted above deck level will give far more range than regular Wi-Fi at deck or cabin level.


  • Install marine-grade waterproof high-gain omnidirectional antenna. Non vented type suggested as any water ingress into the antenna will reduce the life of the antenna. Avoid the use of dish or directional antennas.
  • Install weatherized Ethernet device (e.g., Bitstorm BAD BOY Xtreme, Ubiquiti Bullet, SENAO SL-2611CB5 EXT or SOC-3220) as close to antenna as possible in order to eliminate signal loss in antenna cable. (See picture at right for an example mounting using the Ubiquiti Bullet 2HP.)
    Masthead Xtreme

    Masthead mounted Bitstorm Xtreme resulting in no signal loss due to cabling.

  • Run outdoor rated CAT5 cable from Ethernet device.
  • Devices are powered via Power Over Ethernet (power requirements vary by manufacturer). Some devices operate directly from 12Vdc.
  • At cabin end of Ethernet cable, attach:


  • Install marine quality USB device with non-vented omnidirectional antenna mounted next to the WiFi adapter. (e.g. The Wirie)
  • Run the USB cable into your boat from the WiFi system.
  • Extend the USB cable as needed to location inside your boat. Use Active USB extension cables to extend the length.
  • Install software for the WiFi adapter on any computer you want to use with the WiFi adapter.
  • If desired, set up Internet Connection Sharing on a single computer to allow multiple computers/devices to access the USB WiFi device simultaneously.

Hybrid Solution:

  • Install marine-grade waterproof high-gain omnidirectional antenna mounted with a Hybrid WiFi Adapter/Access point (e.g., The Wirie AP) .
  • Antenna should be non vented type as any water ingress into the antenna will reduce the life of the antenna. Avoid the use of dish or directional antennas.
  • Run marine grade DC Electrical Cable to a 12V power source.
  • Connect to your local HotSpot over WiFi to manage both your local network and the shoreside connection.
  • Allows all your computers and devices (iPhone/iPad/Android) to share the internet connection and manage the connections to shore.

Managing a Wireless Ethernet Bridge Edit

Wi-Fi Boat Permanent

Wi-Fi at top of sailboat mast

When using a wireless Ethernet [client] bridge, IP addresses of networked clients on the boat (wired or wireless) are normally assigned by a shore-based DHCP server.

The problem is that the wireless Ethernet [client] bridge will typically have a fixed IP address for management that won't necessarily be on the same subnet as IP addresses set by shore-based DHCP servers, preventing networked clients from directly managing the wireless Ethernet [client] bridge.

Possible solutions to this problem:

  1. Use two network adapters {wired or wireless) on a given networked client:
    1. One configured by (shore-based) DHCP for Internet access
    2. The other configured manually just for managing the wireless Ethernet [client] bridge
  2. Use a multi-homed Ethernet adapter with both a static address and a DHCP address
  3. Use a client (ethernet adapter) that incorporates a router to create your own LAN (example Bitstorm BAD BOY Xtreme and Express). By adding a simple network switch, you can share the internet simultaneously with several computers.

Wired versus Wireless Clients Edit

Boat Wi-Fi Wired vs Wireless

Note: In order to minimize possible interference, a boat Wi-Fi access point should ideally be on a different minimally-overlapping channel (1, 6, 11 in the USA) from the shore access point.

Power Edit

Many standalone low-end networking devices that use separate "wall wart" type power supplies are able to tolerate a relatively wide range of input voltage, and can be run directly from 12 VDC boat power with an appropriate adapter cable. Check manufacturer input voltage specs if possible.

One advantage of the Ubiquiti systems (the Bullet 2HP or the Nanostation 2HP) is that they run on power over ethernet which can be "injected" using a passive PoE injector (like $5) wired straight into 12VDC. Getting an injector with separate power and lan leds is a good idea, since you can figure out the polarity without having your device plugged in.

LAN on a boat Edit

  • When the boat has its own wireless access point (or wired hub or switch), and multiple network devices that get their IP addresses from a remote DHCP server, then all those IP addresses will be on the same subnet, and are thus part of a local area network (LAN).
  • It won't necessarily be a private LAN -- unless the remote wireless access point implements wireless-to-wireless isolation (which many do not), all boats will be on the same LAN, and should take precautions accordingly -- see Secure Internet access in a public hotspot.
  • That kind of LAN will be "up" (working) only when connected to remote Wi-Fi; otherwise it will be "down" (not working).
  • To have a private LAN, and one that works even when not connected to remote Wi-Fi, then use a local wireless router instead of a local wireless access point (or wired router instead of a wired hub or switch). That creates a "double NAT" which will usually work fine, although it can cause problems with certain older network protocols and applications. To access the LAN management port of the wireless Ethernet (client) bridge:
    • Good method: If supported by your local wireless router, configure a manual route from LAN to WAN for a (RFC 1918) private IP address on the LAN management port. (The wireless router shouldn't forward private addresses without a manual route.)
    • Crude method: Set a fake non-conflicting public IP address on the LAN management port of the wireless Ethernet (client) bridge, which your local wireless router will automatically forward to its WAN port (since it's not a local or private address).

Relaying and Mesh Networks Edit

When some boats are too distant from a shore access point for a direct Wi-Fi connection, it may be possible to setup nearer boats to repeat or relay the Wi-Fi signal to more distant boats. See Wireless Distribution System.

International Use Edit

Wi-Fi channels are standardized, but vary slightly in different parts of the world. Many Wi-Fi devices will work properly anywhere in the world, either by means of a configuration option (preferable), or by means of different firmware loads (clumsy). See Wi-Fi Channels.

External Links Edit

  • The Wirie - Long Distance, Easy to Use, Simple Installation, Affordable - Marine Grade, for Boats and RVs
  • Wi-Fi for Boats - You Can't Connect To A Station You Can't Hear
    Use our 15 dbi High Gain Omni Antenna to hear the weak signals.
    "It works beautifully!" Bill Campbell, S/V Alcheringa II

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