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Wi-Fi access for Boats

July 2016 Update:  Xfinity and Time Werner are now beginning to make public access hot spots available in many areas.  For customers of theise companies they are able to connect and have internet access in many locations.  We found this to be true in many locations along the US East Coast ICW from Marathon Florida to Washington DC during the spring of 2016.  Boats that are not subscribers to Xfinity can subscribe to their hot spots by the hour, day and month.  When doing so, Xfinity records the MAC Address of your system and automatically validates your connection whereever you may be. 


January 2013 Update:  The level of interference from competing Wi-Fi signals in the US continues to increase and the number of stations using Wi-FI security is approaching 90%.  This is limiting the ability of customers to find an open or public Wi-Fi signal greatly. It is increasingly necessary to pay for a data connection or in the US from a local marina or vendors such as Beacon Network.  Outside the US this continues not to be a problem.


August 2011 Update:  In the United States there is an every increasing number of Wi-Fi stations causing an ever increasing amount of interference with one another. In addition, the rapid adoption of Wi-Fi security is making finding an open or public Wi-Fi signal more dificult to find in the US.  Thankfully this  has not happened to as great extend in the islands.  Friends using my equipment in the Islands continue to report comonly anchoring 1/2 to 3/4 mile and more from island hot spots with reliable connections capable of high speed internet and Skype Video calls through out the Caribbean, Europa, the Med and across the South Pacific.

Below is the talk I gave in 2009 to the crusing community in Annapolis MD.

This discussion is a factual presentation of Wi-Fi the technology available tempered with years of practical experience in what is, and is not reasonably possible.  I spent eight years on my boat Quietly in the Caribbean building Wi-Fi systems for myself and friends.  Before that I spent 30 years in the computer and networking industry building computer systems and high speed data networks.  In 2010 I returned to the US and am once again working in the computer industry.  Wi-Fi for boat is my dedication to making crusing fun and easy for those of you out there doing it!

Can a typical boat cruising the Caribbean or US waters really have a 7, 5 or even a 3 mile Wi-Fi range?  I see a lot of exaggerated claims on the Internet for Wi-Fi ranges of several miles.  In my opinion, these claims are disingenuous as best.  Reasonable expectations for a boat at anchor with a typical external 6to 9 db USB Wi-Fi Antenna is approximately 1200 feet. 

To increase this distance requires high gain antennas and commercial grade equipment.  Using such equipment a range of 1/2 and sometimes 3/4 miles for fast reliable Wi-Fi from a "Hot Spot" Wi-Fi signal is reasonably possible.

That said...  it is possible to provide Wi-Fi to a fixed slip or mooring over a distance of several miles.  This is similar to a commercial point to point link using good equipment with highly directional yagi or parabolic antenna on shore carefully aimed directly at your slip or mooring.  In this case, you could have reliable Wi-Fi at a distance of several miles while at your mooring or slip.  When away from your mooring or slip you would have the more common ranges discussed above. 

Commercial vs. Home Equipment

What makes one Wi-Fi system different than another system is intended use and how the manufacturer designed the equipment to function in that intended use.

Wi-Fi was originally envisioned as a simple way to connect several computers in a conference room. Over the past few years more powerful equipment, up to about 200mw, become available for home and Wi-Fi Hot Spots.  All of this equipment use similar if not the same internal components to extend the range from a few feet in the conference room of years past to cover a larger area such as a restaurant or small office.

Home/Office equipment is often be a small radio called an Access Point with one to three short antenna's and perhaps 100 - 200mw of transmit power.  These are excellent when used in a single room or perhaps in an adjacent room in your home, or a coffee shop, restaurant or small office.

Commercial equipment is made for very different use, often making quite long range point to point connections of up to 20 miles.  This equipment has much more transmit power of typically 1000mw.  However, it's not only the commercial equipment's transmit power that makes this possible.  These long distance commercial Wi-Fi systems use special purpose very high gain antennas to make connections at these distances.

Antenna's have a characteristic called gain which depending on the antenna design can focus the transmitted energy and also act like a big ear to hear a weak signal. 


Think of it like this. The design and shape of an antenna can act like a physical amplifier extending the range of the equipment.  Remember the megaphone the high school cheer leaders used. It focused the energy of their voice making it seam like they were shouting louder.  And think about what happens when you cup your hand around your ear to here someone a long distance away... your cupped hand gathers more sound making it sound louder.  Commercial applications use very high gain parabolic antennas to make long range connections using these principals of focusing and gathering energy.


Very high gain long distance parabolic antennas used in commercial applications typically have a gain of 24 db or 256 times the signal strength that the transmitter is actually putting out. And when listening, receive signals that are 256 times weaker than possible without the antenna.

These antennas emit a pencil beam of RF energy and can receive very weak signals.  They provide enough gain to literally bounce a signal off the moon and the receive sensitivity to hear the very week echo from the moon.  Ham radio operators have been doing that for years at these frequencies. Long range links of 20 miles are possible using such equipment, but the antennas must be aimed precisely and are mounted on heavily constructed fixed towers to maintain their aim.  A boat at anchor, on a mooring, or even tied to a dock, is not stable enough to maintain a connection using these antenna's.

Unfortunately, we must use an omni-directional antenna that can send and receive signals in all directions as we swing at anchor or on our moorings.

To build a good Wi-Fi system, we need to understand the equipment we are trying to connect to.

The typical Wi-Fi Access Point is a 100 to 200mw transmitter coupled to the "rubber duck" antenna that you see on most pieces of Wi-Fi equipment.  This equipment is designed to provide a connection to a notebook computer across a room and perhaps a slower connection three rooms away in your home or office.  I am sure someone here has an Access Point at home that works great in the living room but when you take your notebook back to work in bed it really slows down.

Now imagine trying to connect to that same Access Point and doing it from your boat anchored several hundred feet, or perhaps a thousand feet away.  Now that presents a real challenge!!  And to make matters worse, as cruisers we usually find a "Free Wi-FI" Access Point that is often tucked away in a restaurant or at the marina bar. 

As cruisers, we must make up for the shortcomings of the shore side signal we want to connect to.

If we are lucky, we find a Wi-Fi Hot Spot at the local Marina.  They have almost invariably purchased a small Access Point and may have mounted an omni-directional antenna on the side of their building giving us a clear view of the antenna.  Starting in 2009 I have begun to see a trend of Marina's contracting with several companies that provide mesh networks at marinas. These sites are much better and boats anchored near the antenna can expect reasonable Wi-Fi reception though there is often a daily, weekly or monthly fee for access.

More often, as cruisers we are trying to connect to a "Free" Wi-Fi signal from a local restaurant, bar, or home.  And in these cases, the better our antenna and equipment, the further away we can anchor and have a reliable Wi-Fi connection.



Common Wi-Fi equipment I see on hundreds of boats. 


Many people have purchased a Wi-Fi extender or a USB device with a small 6 db gain antenna they set out in the cockpit and connect to their computer below.  That antenna effectively amplifies the signal they are trying to attach to by a factor of 2 over the built in antenna of their computer.  Many have found 8 or 9 db USB antennas on the Internet that increase the ability to hear the Access Point by a factor of 8 times.  Systems with 12 db antennas provide 16 times the gain, and a system with a 15 db gain antenna would receive a weak station 32 times better.  If it were possible to use a 24 db gain antenna on a boat that would be 256 times more sensitive in receiving weak signals.


As I discussed earlier, there are some practical limits here.  First that 24 db antenna would have to be carefully aimed at the Access Point behind the bar and your boat would have to be aground to provide a steady aim.  That won't work. 


You could use an 18 db sector antenna if your boat would just keep pointing with in 45 degrees of the Wi-Fi site.  I have actually tried that, and you run yourself nuts running out to adjust the antenna every time the wind shifts.  Nice idea but no cigar.



Basic laws of transmission and propagation to deal with.


As sailors we know that mounting an antenna high on the mast increases the distance our VHF radios can talk based on improving the line of sight distance over the curvature of the earth. This is at relatively low VHF frequencies of 150 MHz.


Wi-Fi systems operate at much higher frequencies at 2,480 MHz.  These Wi-Fi signals are more like Radar signals than VHF Radio and like Radar signals, Wi-Fi signals are adversely affected by wave chop which reflects and scatters signals and by water which absorb them.  Your microwave cooks food because of this.  And you have seen these reflections on your radar as clutter when the seas are rough. This is caused by something called the Fresnel Zone effect and raising the base of the Wi-Fi antenna to at least 12 feet above the water reduces it and improves the Wi-Fi signal path over the water by lessening the scatter and reflected signal (noise) that affects both our transmission and reception.  Another reason to mount your antenna high is to give it a clear line of sight over the surrounding boats which will give you a much better and more reliable connection.


Now before you rush out and purchase that good high gain omni antenna and some very expensive LMR-400 cable to mount the antenna on your radar arch or antenna tree connecting it to a Wi-Fi booster, we are fighting a loosing battle.  The battle of signal loss... 

Depending on the type of cable, for each several feet of antenna cable connecting Wi-Fi antenna to the radio you give up approximately 50% or 3 db of the signal.  Also each time you go through a connector you loose more signal. 


You have probably seen a friend's boat where they have an antenna sitting on the boom and several feet of antenna wire often made up of a short very thin high signal loss wire and a longer LMR400 extension with several connectors leading to a Wi-Fi radio or amplifier in the boat.  Yes it is better than nothing and they can anchor close in and use Wi-Fi, but the cable and all the connectors are consuming most of the Wi-Fi signal both on reception and on transmission.  It is better than no antenna but not as good as it could be.  And a cable loss from the top of the mizzen mast or the back of your boat to your computer would be like having no antenna at all.



There is another very important thing to talk about... the myth that a strong transmitter will always connect further.


I have seen a lot of boats in the Caribbean with a big powerful Wi-Fi amplifier putting out such a powerful signal that no one else can connect but still have crummy connections because they can not receive the weak Access Point signal talking back to them.


Remember, this is a two way conversation.  Just because you can shout loud does not mean you can hear a person whispering to you.  You must have balance in your ability to receive (hear) and well as transmit (talk) to the Access Point you are attempting to establish a reliable connection with.



How to solve all of these problems.


The truth be told... all Wi-Fi transmitters and receivers use similar if not the same internal components.  What makes one better or worse than another is how the equipment is designed to operate with its intended use.  The equipment I selected is designed for the harsh outdoor commercial long range environment.  It combines strong transmission capability and very sensitive receivers to hear weak signals.  This equipment has much more in common with our marine environment than the typical extended range laptop, home, or auto extended range antennas you often see in use on boats today.


Next I found a superb 15 db gain Omni Antenna to go with the commercial radio's excellent sensitivity to hear the weak signals.  With this equipment, the distance I am able to establish a reliable connection at is more a factor of the shore side station than the equipment on my boat. 


But the real secrete is this:  The antenna and radio (actually a wireless Ethernet router) are directly attached.  There is absolutely no RF cable loss; zero, nada, zip. The connection from the antenna to my computer is then a standard Ethernet network connection using inexpensive Cat5e network cable which can be up to 300 feet in length. This allows complete freedom to mount the antenna in the best possible location on my boat and simply run the network cable to where ever I use my computer.  And on Quietly I actually connect the antenna to a data switch which shares my single Internet connection with several computers and other equipment on the boat.


Another secrete is that with the very high gain Omni-directional antenna, I do not have to use the full power of the transmitter to have reliable long distance connections. 


Why is this important?


When a powerful transmitter is running at full power it introduces distortion in its own signal and interference to others. With my high gain antenna this allows the transmission power to be set 3 to 6 db lower than maximum rated power.  This gives a cleaner and clearer signal providing a faster, more reliable connection to the shore based system while at the same time being a good neighbor to my fellow cruisers by not blocking their connection with an unnecessary strong signal. 


It is all about balance.  You can not connect to what you can not hear.  And balancing transmit power and sensitive receiver with the 15 db gain Omni antenna gives me greater connection distances. 


Today back in the United States I commonly anchor 2500 feet (1/2 mile) from a shore side signal and have reliable connections capable of Skype Video calls.  In many Caribbean anchorages where there is less interference, I often anchor and reliably connect at a distance of 3500 to 4500 feet from strong shore side signals.


Thanks for listening and I hope you have lots of questions.


Dalton Williams

SV Quietly & Wi-Fi for Boats