By popular request, here's the transcript: Wireless Communication for Cruisers
I gave this seminar a couple of times, on the beach, in Georgetown in early 2009. Some of the commentary is unique to Georgetown, such as the morning net, and WiFi hotspots. It's my notes, so it doesn't necessarily read like an instruction manual (and which it's certainly not), but you might find it useful. (Begin transcript) This will be an Interactive seminar - participation from audience, questions and answers. If you can hear me in the back, stick up your hand. I'm not a communications professional - just a hack who's learned at the school of hard knocks. Saying: Experience is what results from making mistakes - Another: Experience is the best teacher, but has very high tuition. So, what I've learned is mostly from making mistakes (smiley) This could be extremely technical, except I expect we'd lose most along the way. So, I'll try to keep it very simple, in layman's terms. Questions are welcomed and encouraged. If I don't know the answer, I'll say so, and call for my audience lifeline. If those of you with vastly more experience than I hear me make a patently wrong statement, please not only call me on it but also provide the correction. For those who'd like one, there's a box of boat cards here - if you take one, drop me a line on the Internet, and if you have one, leave one of your boat cards. So, with that as a preamble, let's get started. First off, let's define what I mean by wireless. That's communication that's not tied to a landline of any sort - telephones, telegraph, etc. The quality of those communications is largely defined by "ears" and "mouth" quality. Antenna is ears, and transmission power is mouth. If you have big ears and a big mouth, generally speaking, you can communicate better than those with smaller ones. In this case, "size matters" - but it's not necessarily physical size. We'll look at this a lot as we go along. "Ears" are generally defined by gain - shown in decibels - and bigger decibels is better in general, if you want to hear better. You pretty much can't get in trouble with bigger ears - other than some stuff I'll talk about in the section on wifi. "Mouth" is generally defined by amplification, usually shown in watts, and depending on the type of radio you have, you may be limited in the watts you can use by regulation, or by the type of radio you have, or, simply, the power available to you. In every area we'll look at today, these principles will hold true. Is there anyone here who isn't here as a result of hearing an announcement over the net in the mornings? Great. That's VHF, just one of the areas we'll cover - so, since you're all familiar with this means of wireless communications, we'll start here. As I said in the beginning, wireless communications is all about ears and mouth. A better antenna will hear better, and more power will be heard further - you can "shout louder". And, in general, height is your friend. You'll hear me say that more than once (smiley) However, there's some problems with that, and in any instance, the antenna is the in and out point. If your antenna isn't up to snuff, and all the connection details between it and your radio, you won't hear or be heard. And, as was pointed out yesterday on the net, if you're on high power, you may bleed over into other frequencies when you're nearby, which is why we're requested to go to low power on 68 after the net. In wireless communication, "shouting too loudly" is referred to as an alligator - a really big mouth, which sometimes hurts folks. So, you have to adjust your power to the circumstances. In general, using only enough to be heard is the best, especially when you're paying for power in the sense of having to have a battery to support it! The USCG has really big ears, and a very big mouth, as those of you who've ever communicated with, or even just listened to traffic coming from them, over 100 miles away know. However, some of that's a function of antenna height, and they can also direct that big mouth in the case of an emergency so it doesn't overcome everyone. I expect most here have omnidirectional antennas - ones that listen and talk relatively equally in all directions. On a moving platform, that's the best. The Coast Guard's emergency communication would be done over a directional antenna - one that works best in only one direction. It's also how their several stations can triangulate on a signal, whether to respond to an emergency in an unknown location, or to track down someone misusing the VHF frequencies. Some of you may have heard the CG berating someone in the general area of X/Y for misusing channel 16 - that's how they did it. Having said all that, most of which I assume you know, there are some bleedover facts which will apply to other areas we'll talk about. One is that in order to be heard, you have to get the signal from the radio to your antenna, and to hear, you have to get the signal from the antenna to the radio. Many things can affect the quality of the signal you try to send up and down the cable, but that's another seminar entirely. It's enough to say that interference or quality degradation can come from lots of places, and sometimes tracking it down is enough to make you want to tear your hair out, assuming you have some! In the frequencies used by VHF, generally speaking, your communications are practically limited by line of sight. For most boats, that will be about 25 miles due in part to antenna height and power out. Pretty good, for most coastal communications, or between boats and sometimes to shore points like marinas and businesses. I'm sure there are those of you who have hacked the frequencies on a SSB radio to communicate much further with the better antenna and more power available to the SSB platform - but that's another seminar, too (smiley) And, finally, the newer radios have some digital communications capabilities. One is the DSC emergency button, which only works with a GPS input, to tell those receiving the alarm where you are. The other is the MMSI numbers, which allow you to call a given station directly rather than having to hail and wait for a response. It's about like dialing a phone - only that number answers. Are there those here who use this regularly? Great. I'm going to point questions in this area to you cuz I'm not up to speed on that! As you've all used this VHF form of wireless communication, we'll move on unless there are questions - ? Moving up the scale, we have High Frequency Radio. HF radio in the marine world is generally either SSB or Ham. Just like the VHF morning net here, there are nets in both SSB and Ham bands, and you can talk to other stations by calling on a listening frequency and going to another to keep the listening frequency clear. However, HF has other communications advantages. First, you can have a much more effective antenna and a great deal higher transmission power than in VHF. Who here's a general or higher rated Ham? Of those, who has a ham shack at a land-based location? Great! I'll ask you to chime in on questions, as you're far more qualified than I am! Back to the ham shacks. Some of these may transmit with thousands of watts - much easier with land-based antenna systems and ample power available. Most marine radios will be limited to about 150 watts, and eat up power at a rate of about 30 amps if they use it all. All tradeoffs of our marine lifestyle. However, HF radio has the ability to take advantage of atmospheric conditions to reach out literally to the other side of the world. If you thought VHF quality challenges were frustrating, just wait for HF radio! Antennas, tuners, ground planes, propagation, sunspots, all have a part. I'm assuming this area will be relatively well covered in the various ham seminars available, but I want to touch on a couple of generalities. First is that even 100' of thin wire trailed behind the boat can be an effective ground, when connected to the tuner. A chain hung over the stern or the side, depending on where your tuner is, touching the bottom, can be a killer ground (killer in a positive sense). There are entire books written about making effective grounds, as the ground plane directly affects how effective the signal is in getting out. Second is that there are many ways to make an antenna, from a bent coat hanger, or a few feet of wire directly stuck into the antenna output of the radio, to a wire hauled up on a halyard, to shroud or stays, with or without insulators, or whips. A couple of generalities, however: You don't need a fancy antenna to receive - it's output where that gets touchy. As to output, if you have metal nearby in a parallel plane to the antenna, it will suck the signal power out of your transmission. Running a cable, and, worse, the actual antenna, next to a shroud or stay, even with standoffs, will suffer great signal degradation. Thus, a free-standing whip, usually vertical, unless it's parallel to some other nearby metal, will generally be effective at getting the signal out, all other things considered. Another generality is that you'll want the shortest cable between your tuner and antenna possible, as signal will bleed out of the cable in a direct relationship of the length of the connecting cable. And, finally, with the higher power available to HF radio, if you touch the antenna during transmission, you can be burned. Here, again, there are entire books written about antennas, as those determine your ability to transmit. The challenge with HF radio antennas as compared to VHF is that there are so many frequencies, and, to achieve the long distances, you need longer antennas, in general. Because effective transmission is a function of antenna length directly related to the frequency you're using, and because it's difficult to adjust your length for each frequency you use, most HF radios will also use a tuner. The tuner electronically fiddles the length of whatever it is you're using for your antenna, to match the output of the frequency you're using. Most boats will use automatic tuners, but some hams will prefer to manually do the fiddling - but not on a boat! Just as in VHF, height is your friend, and, because of the frequencies involved, generally speaking, so is length. That's why, in sailboats, it's so common to see backstays, pretty much the longest point from here to there on a sailboat, used as antennas. However, the signal doesn't go out evenly from there - the line isn't straight up and down - but the length, in general, overcomes those shortcomings. Most powerboats, deprived of that great length, will use whips. They have the advantage of being able to be vertical, enhancing the signal transmission and reception. They, too, are connected to a tuner, which automatically adjusts the electrical length of the antenna. Some sailboats, like Flying Pig, use a whip as a backup in the unlikely event of a dismasting, which could ruin your day but also kill your HF radio effectiveness, which might be critical in an emergency! So, all that said, what can you use HF radio to do for communications? Well, you can talk to the weatherman - Chris Parker on BelAmi or Herb on Southbound, for example. Some of you may have heard me from time to time talking to Chris on 4045, early in the mornings. You can talk to a buddy boat, either right next door, or hundreds of miles away. You can talk on one of the umpteen nets, nearby or halfway across the world. If you're a Ham, you can talk to a shore station who will do a phone patch so you can talk over the phone, albeit with a PTT - and the folks on the other end will probably try to talk over you cuz they're not accustomed to waiting until you say "over"! - but it beats not talking to them at all. Using a special interface, usually referred to as a modem like the old dialup days for Internet, you can get and send email, over the AirMail, Ocens (Xnet), and other programs for SSB and Ham. You can receive weather reports and grib files - visual depictions of wind forecasts - in the same fashion over the AirMail and similar programs. HF radio also has the DSC alarm and MMSI functions if you've got one of the newer radios. SSB was originally designed for business - but the advent of satellite communication has pretty much left those bands unused by commerce. However, it does specifically mean that you can talk about business things over those bands, where you can't over Ham bands. All these things are possible over HF radio. The ears and mouth benefits and restrictions bits are pretty much the same deal as in VHF - except that too much mouth and you can distort your signal. In fact, clipping - an automatic shutdown of power if there's too much - became an issue on some IC M802s, and while you had to pay to get it to them, Icom did upgrades to overcome the problem, and shipped them back on their dime. So, HF radio is like VHF on steroids, except that there are certain frequencies you can't use if you're not qualified, weather and sun conditions have a great deal more to do with whether you'll hear or be heard, and you can use it to get and send email and get other visual data, as well as connect to a landline telephone. As Ham is the subject of many seminars here, I'll leave this for now, unless there are questions? Moving up the frequency scale, we have cellular telephone communications - just another form of radio. Is there anyone here who has not used a cell phone? Here, too, we have the same ears and mouth considerations, except that we're pretty much limited in what we can do about the mouth part. In the early days, there were analog phones - who here had a bag phone? Anyone still have one? And able to use it? Early on, there were relatively few cell sites, and so you had to have greater transmission power and receiving sensitivity. However, to limit the time on any one cell, more cells were built, and the industry went digital. With the digital conversion, power output and antenna sensitivity was reduced, not only for miniaturization but to limit overlap of signals. Today, it's very difficult to have an analog signal, but, as long as you could find them, analog phones could communicate over much longer distances than the current digital phones. That's because along with the digital revolution's reduction in power and antennas, today, you don't generally get much distance from a cell before you can't make a call. Yet, the cellular revolution has made it so that many people on shore no longer have a landline phone, provided by one of the conventional telephone providers. That, and the huge advances in technology, has made cellular phones nearly universal for voice, and even picture, communication. Instruments like Blackberry, iPhone and others have made it possible to be on the Internet over a phone. Some actually connect to open Internet sites over an internal wifi adapter, and others use their cellular network to integrate to the Internet. There are connectors which will allow you to dial up an Internet service provider from your cell phone, providing the data link to your laptop, when you can't see an access point over your wifi adapter. An access point is a site that can connect you to the Internet, over wifi. We'll cover wifi separately, as it's not a cellular issue, but I'll address the internet connectivity part of the wireless communications here. I'm assuming that cellular telephone use for voice communication isn't a mystery, but just in case, I'll pause for questions on that. So, on to Internet connectivity using cellular communications. There are several interfaces using cellular technology that can connect you to the Internet. One is the AirCard or equivalent. This is essentially a cellular phone (again, just another form of radio) which plugs in to the PCMCIA slot in a laptop, but it just does data. Others can plug into a USB slot, whether on a laptop or desktop computer. In these cases, the cellular provider acts as the Internet service provider - usually known as an ISP. Various providers will allow limited or unlimited data access, all at a price, and usually accompanied by the same sort of contract requirements that are present with the usual cell phones that aren't pay-as-you-go. Some cellular providers will allow you to use your actual cell phone to connect to your computer over an adapter cable. Both cases are dependent on your being in the range of a cell. For coastal cruisers, or those in the ICW, these can work very well. However, in each case, these are one-device providers. That is, the connection is for one computer only. If you have more than one laptop aboard, you'd have to have one for each laptop in order to use them at the same time. There's another solution, however, which can be used on a stand-alone (in a single computer) basis, or, using a special router, designed for the purpose, you can have your own wifi access point and cable hub. I have a friend who's used this technology up and down the US East Coast, in and out of the ICW, using his and his wife's laptops simultaneously as they pursued their masters' degrees in education. Their connection and speed was such that they were actually able to broadcast streaming video as they went along in Maryland on the ICW. However, as with all cellular communications, it's dependent on being within range of a cellular provider. This device can, of course, be taken into a landside home and used there as well. His is from Verizon, tied in with their handheld cellular service. There may well be others that would work, but it takes a special router to accept the USB input and power the unit. His is http://EVDOinfo.com for EVDO routers. KR2 - it's not cheap, but it works. You could also do a search for IslandSpirit35 and broadband and get to his blog for more detailed information. If I were a US coastal cruiser, only, that's what I'd use, as cell sites abound, the throughput is great, and it allows more than one computer to be online at the same time. On Flying Pig, Lydia and her mother have separate laptops and I have a built-in 12V system, all of which run off a router. The ability to not have to be connected to (only) one device at a time is a big deal with me. I'll cover that in more detail in the wifi section today. So, cellular communications come in a variety of flavors and styles. You can call anyone you have a phone number for, send text messages if the recipient and you have that feature enabled, send pictures, again if your phone supports it and has that feature, non-telephone devices can be used for data, including internet, and a handheld cellphone can be an internet device. Dick Tracy technology is here in real life, today! - that is, of course, if you're within range of a cell which supports your cellular provider's device. Unfortunately, it's not a secure connection - frequency sniffers can intercept communications over cell phones, and people as lofty as Prince Charles and Camilla Bowles can attest to the lack of privacy in cellular communications, so be careful of what you say! And, the same goes, of course for Internet traffic over a cellular connection. Back to the big mouth and big ears, there are tweaks you can use to boost your reception and strength, but for most folks, the way they use their phones, it's not a biggie. However, if you're in fringe areas, such as near shore but not coastal, external antennas and signal boosters exist that might be of interest to you. Think of the older car phone technology, with the big antenna on the back, and, today, the little whip attached to the rear window. If you get the antenna out of the tiny phone in your hand, and can boost the power, you can achieve a bigger ear and mouth. I'll leave that to research on the web for those who may need it, or if there are any here who've used that solution, I'd invite your comments at this time. Before I leave cellular communications, I'll add that today's technology allows you to make and receive calls all over the world, with phones which can be adapted for different parts of the world just by switching out a chip. However, as I'm sure you've discovered, there are certain parts of the world, the Bahamas, for instance, where state monopolies make it a bit more difficult to be seamless - other than at a great cost, relative to services elsewhere. None the less, you CAN communicate here. Any questions on cellular communication? Moving up the frequency scale, we have satellite phones. At least today, those phones are still pretty big and clunky, with big antennas, similar to the very earliest cell phones. Just like the VHF and HF radio comparisons, however, it's a bit like cell phones on steroids. The advantage to satellite phones is, of course, that you can use them in the middle of the ocean, and adapters allow you to connect to the internet, albeit at dialup speeds, at the same time. Of course, you're limited, just like cell phones, to being able to see, in this case, the satellite, and various providers have better or worse coverage, depending on which part of the world you find yourself in. They come at a cost, of course, and the time on them is extremely dear in comparison to cellular phone time. Yet, in an emergency, a satellite phone and a handheld gps might trump an EPIRB in that you can directly communicate the nature of your problem along with your location. Satellite phones use a frequency that is more sensitive to lots of signal degradation, so, for most cruisers, an external antenna adapter is needed to get the antenna out of the boat. Yet, for all the hassle, the satellite phone provides the primary means of communication for some cruisers, acting as their voice contact with the outside world and internet interface. Are there any here who use a satellite phone on a regular - that is, not just in case of emergency - basis? Would you care to share your experience and provider? Now, finally, to the top of the spectrum - wifi communications. WiFi, or Wireless Fidelity, uses a standard known as 802.1x, with the most common today still being 802.11, with several flavors. These operate on a frequency near 2.4 gigahertz, or 2.4 trillion cycles per second. That makes for a very short wave length, and nearly anything in the way of a visual line between the antenna and the transmitting point will decrease the efficiency. Virtually every laptop sold today will have a wifi adapter and antenna built in. However, those have the limitations I just mentioned, so unless you're in the same building as the transmitter, or very close by, you may not see the signal. As many are not really familiar with what's happening when they log on to a connection point, I'd like to back up a bit and define what's happening. For those with a land-based operation (you still have a home to go to), in all likelihood other than in remote areas, you'll either have cable, DSL (digital subscriber line), maybe fiber-optic or perhaps satellite providing your internet signal, unless you're a mega user, in which case you may have a T1 or T3 line, or even more. As those last two are unlikely for most, and those who need them know what they are, I'll leave those alone for now. In any case, however, those come from an ISP - Internet service provider - to your home or business. Those provide the gateway to the Internet. >From that signal point, you may distribute that signal through a router. It might be wired, with Ethernet cable, but, more likely, it will be a combination of a wired and wireless router. The router assigns an address to each computer, and directs the traffic, so that data goes to the right place. So, if you have more than one computer, all can get the right information that they need. For those of you with such a facility - a home or business with a router - you have the choice of just plugging in the router, at which point it will usually work just fine. However, if you go into the setup instructions, you'll find that you can change the default settings. For example, you can name your router something meaningful, such as the one on our boat, which starts with Flying Pig. You could also limit the number of computers which could connect to the router, or block certain computers from connecting at all, or from accessing certain points on the internet, or, even, provide an encryption requiring someone to log in with a password. With that as background on how the signal gets distributed, if you just plugged in your router, and you wanted a laptop to go on line, the wifi adapter (the thing in the laptop which sees the signal and interprets it) would show you the available places you could sign on to. If you named your router, it would show that name. If not, likely it would show the name of the manufacturer, such as Linksys or Belkin or others. It might well, if you were in a crowded neighborhood, show you other points you could connect to. In fact, if you didn't have your own Internet service provider, it might allow you to connect to someone else' Internet connection! Now, all this has assumed your having a home or business. However, here you are, out in the middle of the sound, and you "look around" - that is, your wifi adapter looks around - and depending on where you are, you may see gaviotta bay, harbour wifi, linksys, or a bunch of others, all showing up as "open". You may also see a bunch of others, which are shown as encrypted, typically with WEP or WPA protocols. If you have the passwords, you can sign in to those encrypted sites; everyone else is left outside drooling over the prospect of being able to connect to the Internet. I want to talk a bit about ethics. Early on in the days of wifi, there were lots of discussions about "stealing signals" - using someone else' Internet service provider, essentially, because if you signed on to someone else' account, you were using their service. In addition to the ethics of that, the concern was that if many were using the service, bandwidth would suffer. As time went on, knowledgeable folks frequently left their routers - the thing connected to the ISP - open intentionally. I've even got another buddy who built a "cantenna" - a home-made, very high gain, very directional, antenna, hung it high in a tree, and pointed it at the local air force base, to provide servicemen there a signal where there would otherwise be none. Other knowledgeable folks encrypted their routers in order to prevent anyone from using their signal, or out of concern for the ability to compromise one of their computers connected to their system. Whether or not they were likely to be vulnerable, they chose to limit access to their system. With today's broadband capacities, unless the owner was a major power user, in which case, it's nearly certain they'd encrypt, anyway, there is bandwidth to spare. It's pretty typical that the novice computer networker (for that's what we're talking about - you're signing on to a network when you connect to a router) just plugs in their router, and that's it. It's those Linksys and Belkins you see all over in highly populated areas, unless, like my buddy who built the cantenna, a MAJOR power user, you prefer not to identify yourself at all, and intentionally leave it that way. Then, there's the Denny's, Starbucks, McDonalds, Eddie's Edgewater, Day's Inn, Holiday Inn, and a host of other restaurants, hotels and other businesses who leave theirs open, just because it's more trouble than it's worth to deal with folks having difficulty signing on to their systems which are, of course, intended to benefit their customers and/or to attract business to them based on the ability to get a signal. So, today's ethics largely have folks signing on to whatever signal they can find. Whether you're comfortable doing that is up to you. And, if you're uncomfortable, you may not have a pay site, such as gaviotta bay or harbour wifi, here, available. So, without getting into an ethics discussion, let's talk about ways to increase your ability to communicate over wifi. We have the same big mouth and big ears challenges with wifi as in the others. It's complicated by the relatively short distance capabilities of the usual built-in adapters. I'm going to stop for a moment and do some definitions here. A wifi adapter is a receiver and transmitter of wifi signals. It's either built-in, or connects to, a computer for bringing Internet signals to the computer. It's part of a network. An access point is something that distributes wifi signals. It's identified by the wifi adapter by an SSID - an identifier that shows which one it is, and it will have something called a mac address - something unique to each piece of network hardware. Wifi adapters have their own mac addresses too. Mac addresses assure that traffic goes to and from the intended points, and not somewhere else. An access point can be part of an internal network, or connected to an ISP. An ISP is an Internet Service Provider. Without the ISP, nothing happens between you and the Internet. An antenna can be integral, or separate from, a wifi adapter. The higher gain the antenna, with some limitations, which I'll discuss later, the better you can hear. An amplifier is something that allows the antenna to send the signals you put out further. Like in HF radio, the shorter the cable between the antenna and the amplifier, the better, because signal loss is severe in the 2.4 gigahertz band. And, finally, a bit of tech-talk in non-technical terms, so you understand what's happening when you're communicating over the internet (or any network, for that matter): Traffic is passed in packets, which have headers and footers. The header tells where it's heading (the mac address), as well as the number of the packet, and the footer tells the computer when that packet's ended. The header allows your computer, or the receiving site (such as an email address), when you're sending something, to get it - but it's all over the Internet, and packet sniffers could see those packets. That's why when you're ordering stuff over the internet, or doing banking or other sensitive stuff, typically it will be on an encrypted site - to protect your information from prying eyes. Those packets - thousands of them, sometimes - arrive, not necessarily in order, and not necessarily all successfully. The headers and footers allow the computer to be sure that all are received, and then puts them together in the order they belong. If they don't all arrive, it keeps trying until they do, and then sends a completion message so the sender doesn't keep trying. It's a little like someone tossing you a book. If it were bound, it's easy - but it weighs a lot. Unbound, tossing it would make all the pages jumble, but any given page wouldn't weigh very much. Because of the page numbers, you could gather up all the pages, assemble them, and read the book in proper page order. That's essentially what your computer does for packets which then are interpreted as text, images, sound, or all three. So, here we are. Is there anyone here who hasn't logged into an SSID over a computer? Ok - so we're all on the same page. Now, how to get those elusive signals? It's the same big mouth, alligators, sometimes, and big ears discussion, all over again. Unlike HF radio, you can't use the atmosphere to send this information back and forth - it's pretty much line-of-sight. And, due to the nature of the gear, the power levels are tiny by comparison to the other radio gear aboard. And. boats are moving targets, even if they're just at anchor, making it more complicated due to the line of sight limitation and the antenna limitations we'll discuss. Further, there are some limiting considerations for big mouths and big ears. Let's start with big ears, because if you can't hear them, it won't matter how big your mouth is. The linksys variety of router will have a low power transmitter built into it, typically under 70 milliwatts, and relatively low-gain antenna(s). That's because it's usually only used in a single building. However, signals usually leak out of it unless there's a knowledgeable person behind it adjusting the power. It's those signals that you'll sometimes see as you travel. The commercial systems, such as gaviotta bay and harbour wifi will have powerful antennas and amplification to make their signals go further - so they can get you to sign up with them, even if you're all the way on the other side of the harbor. So, back to the big ears. Bigger is better, right? Not so fast. The antenna on your handheld VHF is pretty small in comparison to the one on top of the mast, right? Yet, it's pretty good. The higher the gain, the flatter the pattern of the signal you both send and receive. If your handheld has an antenna of 4-6 inches, it's likely a "rubber duck" antenna. In the wifi spectrum, a rubber duck will typically have a gain of about 5 dbi. The pattern of that gain is sort of like a donut. Pretty fat, and when you slice it, the inner part and outer part look sort of like an egg with the narrow part in. That pattern doesn't miss much - but it's not very powerful, either. Moving up, a common next-step is about 8 dbi. Usually, those will be stand-alone antennas - that is, they won't be directly connected to the router or built into the wifi adapter. In those, the donut's squashed a bit - it goes out further, but doesn't have the height. If you consider the donut as the area you can hear, and the middle of the donut body being the "sweet spot", the higher gain antenna won't paint as wide a pattern on the shore, where you might want to see someone on a hill, or, worse, not see someone close in, under your antenna. Next typical would be in the 12-15 dbi range. Same song, different verse. Cats are better suited to this range, as they don't rock around as much as monohulls, and thus don't miss as much as the antenna moves. However, they've still got the problem of not getting the pattern (the area where the signals are seen or heard) up or down from where the antenna's located. If that's not enough, you can also buy these with various levels of downtilt built into them. That is rather than look like a flattened donut, they're a little more like a fat Chinese umbrella. 7 degrees is pretty common, but you can find them at up to 12 degrees downtilt. If you're offshore, you might be hitting the water, instead of the shoreline, so downtilt has its limitations. On the other hand, if you're pretty close in, and you've got this at the top of a 60 or more foot mast, it might allow you to see a point you'd otherwise look right over, electronically speaking. Two cases in point will be mentioned later. All of these have been omnidirectional antennas. That is, they see, relatively, as well in any direction. There are also directional antennas, which typically can have higher gain in a smaller footprint, because all of the effort is aimed in one direction. Other than in a marina situation, these aren't much good for cruisers, but if you have the means to effectively keep a directional antenna on your target, they can be very effective. All of these also require a point to connect to an adapter, not necessarily a simple thing on a laptop. Now, on to the big mouth part. The typical Linksys router has about a 69 milliwatt output. Put that together with a 5dbi rubber duck equivalent antenna and it won't go very far. On your end, if you can hear it (with the antenna gain we've just talked about), he won't hear you unless you shout. The typical laptop puts out a very small amount of power - because it's usually going to be used in a very close environment. Thus, you may be able to see a site, but not communicate with it. What to do?? There are several options, and depending on your situation, any of them may work well for you. I'll start with the simplest and work up. In any case, remember that height is your friend. The higher you can get your antenna, in general, the better. It's the same as with a VHF antenna - height gets you distance, as WiFi is line-of-sight. First is an externally mounted wifi adapter/antenna combo with a higher gain and more power. These will typically be connected to your computer by a USB cable. Here's an example of a 6.5 dbi gain directional adapter/antenna (hold up the desktop Hawking 6.5dBi USB). I used it in the yard during our 3-year refit on Flying Pig, and it worked well, because I was able to orient it to the signal I was using. However, it's not an external antenna, and it's got a pretty short leash, so I was faced with making it not only go out my porthole, but protecting it from the weather and having a cable which could extend it. External adapters will require something called an active USB cable. They amount to a single-point hub, and carry power as well as data. They come in 16-foot (5-meter) lengths and can be combined for up to 80 feet. While this one's directional, there are others that are omnidirectional. Regardless, all require the power provided by the USB connection - and thus the need for the "Active" cable - they aren't just antennas, they're adapters. Because they're feeding data to the adapter, which has the antenna attached, you don't have signal loss - but you do have a power consideration. A step up from this is something that has become pretty common - a higher gain, USB-powered, omnidirectional stick antenna, with the adapter attached to it. Being attached directly to the antenna, even though it's a high-gain antenna, you don't have a signal loss due to cabling. One such, which has found fairly high usage in the cruising community, is the Radiolabs unit. You can find these at RV sites on the Internet, as well as at marine dealers. You can haul these up the mast or otherwise raise them above the deck - remember, height is your friend - to improve your signal reception as well as propagation. They come in a variety of strengths, both on mouth and ear considerations. 100 to 150 milliwatts and 8 dbi are common. The downsides to this sort of antenna include that, just like the HF antenna, if you've got it lashed to the shroud, the shroud will eat a lot of the signal output. Also, if it's not all-weather, you'll have to bring it inside every time it rains. Likewise, you'll have to deal with the USB cable, and it will attach only to one computer - not so good if you have more than one aboard. And, the power, while better, is relatively marginal if you're a couple of miles or more out. Finally, typically these will have two USB connectors, due to the power demands of the higher output - which will mean two active USB extensions if you don't have it right next to the computer. And, too, it's a single-device unit - it can't be used on more than one computer at a time, a big deal with me for our setup. Another way to skin the cat is an amplifier in the middle of an antenna cable between the antenna and a wifi adapter. These can be found anywhere between 200 and 1000 milliwatt, though the 1watt units usually carry some sort of restrictive stuff about licensing, because they're such a big mouth. At that, consider that the highest I've mentioned is only one watt, compared to the VHF and HF radio outputs. That's why distance is so hard to achieve in WiFi. However, the cable length is the bigger issue. At 2.4 gigahertz, signal loss is significant over long distances such as up a mast. Therefore you'll commonly see antenna cabling as big as your thumb to try to overcome that. Nonetheless, many people see this as an effective solution. The amplifiers are typically mounted in a weatherproof box, and attach to the mast, with the antenna mounted on the top of the mast. They have to be bi-directional in order to amplify the signal in both directions, and, to minimize the loss in either case, are best mounted midway between the antenna and adapter. The next step up, the one we've chosen, is to put an adapter at the top of the mast, in a weatherproof box, with a high-gain omnidirectional external antenna connected to it by a 6" pigtail to minimize loss. It's powered, and delivers data, over Ethernet cable. I'll get into the specifics of this design in a bit, because there's much more to it, but I want to stop a moment and take questions on what we've talked about so far. So, back to our setup. We have an adapter in a NEMA weatherproof box at the top of the mast, which eliminates the problem of antenna cable length. It's also a 400-milliwatt amplifier, so it has the capability to shout back to points a long way away. The power is adjustable in the user interface so that you don't become an alligator, should that be an issue. In the case of WiFi, alligators can overwhelm other local traffic, making them unusable, so, just like in HF radio, you should use only that amount of power needed to communicate. This particular unit has both a 12-volt pigtail connection and the means to use the half of the Ethernet cable not used for data to provide power. We have boat power on that non-data half of the cable, and the Ethernet cable plugs into a single jack in the unit, which is designed to accept power there. That Ethernet cable comes down the mast and runs through an inexpensive power-over-Ethernet (POE) injector. Without being too technical about it, we put boat power to that unit, and it does the heavy lifting, putting the power up the non-data part of the cable. This unit can take 8 to 16 volts, so I don't have to provide a special power supply for it - just straight house power. The other outlet on the POE is a standard Ethernet short cable, which could go straight to my computer. However, I don't have it run to my computer. Instead, I have it run to my Linksys router, which I've named with Flying Pig in the beginning of the SSID. Lydia, her mother, and I, are commonly all on the same connection, which, here off Volleyball Beach, could be harbour wifi, or Gaviotta Bay, both very strong pay sites. In our case, since we've got the "ears" to pick it up, and the "mouth" to talk to it 4 miles away, our actual choice is Palm Bay Beach Resort's free signal. When we can't find a usable free connection, we pay for it, so, here, we could have used Harbour or Gaviotta's very strong pay services. Up on Monument Beach, we had at least three usable open sites in addition to Palm Bay - but they weren't good enough for Vonage, a service that allows free calls to England, Lydia's mother's home. Skype worked though, and because it's cheap enough, despite my not liking having to be tethered to the computer, that's what we've used here. However, using this system, on the way south from New Jersey this summer, 7 miles out, we had a working internet connection over a standard linksys home router's access point; I was doing email and writing our internet log while we were under way and Lydia was on watch. Later, we were able to connect to, but didn't have a big enough mouth to talk effectively to, another open site, 12 miles out. Likely, those distances were achievable due to the 7* antenna downtilt, as our point of sail had us tilted away from shore. By contrast, relative to the sometimes-difficulty with height, when we were doing our refit, there was a site only a few hundred feet away - but our antenna looked right over it. On the other hand, before leaving on that trip, 3 miles out from Tampa, I was able to make Vonage voice over internet calls to England and New Hampshire, and Lydia got a call from her banker on the same trip. That would not have been possible without a very strong connection. Needless to say, we like the way it works for us. There are rather more details than that, but it suffices to say that if you have enough antenna and enough power, you can connect to the internet over wifi at distances you'd never imagine. I'll stop here for general questions, and then, if there's interest, get into more specifics on our system as we have it installed. And, before I forget, the source for this system on a plug-and-play basis is www.islandtimepc.com. Bob Stewart's ([email protected]) the owner and extremely knowledgeable about cruisers, having been one until recently when he moved inland for family care reasons. He's got a new weatherproof device that is a bit stronger, 1000 milliwatts, which attaches directly to the antenna, and doesn't require a NEMA box for the adapter. It looks similar to the Radiolabs' unit, but it supplies data and power over Ethernet, gained from the same inexpensive POE injector as ours, rather than USB. It's not suited for mast-top mounting yet, due to the shock stresses there, but could be mounted in powerboat or arch configurations, but otherwise, in use, it's identical to the one we have. He's also the one who built our 12V-computer system for us. You'll find information about both computers and Internet systems for boaters on his site - www.IslandtimePC.com. Ok, questions: (end transcript) That was it - and it usually had lots of questions as we went along, and I found myself on several boats helping straighten out difficulties in most of the areas, despite my not knowing, really, all that much myself! So, I'm happy to take questions. We're likely leaving this area soon so may not have connectivity for a while, but I'll check the topic, and respond to questions sort of in a bunch, just to save bandwidth. HTH L8R Skip and crew, about to jump off to Lucaya and then to St. Simons Island, GA... Morgan 461 #2 SV Flying Pig KI4MPC See our galleries at www.justpickone.org/skip/gallery ! Follow us at http://groups.yahoo.com/group/TheFlyingPigLog and/or http://groups.google.com/group/flyingpiglog "And then again, when you sit at the helm of your little ship on a clear night, and gaze at the countless stars overhead, and realize that you are quite alone on a wide, wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean; and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends."- James S. Pitkin Morgan 461 #2 SV Flying Pig KI4MPC See our galleries at www.justpickone.org/skip/gallery ! Follow us at http://groups.yahoo.com/group/TheFlyingPigLog and/or http://groups.google.com/group/flyingpiglog "And then again, when you sit at the helm of your little ship on a clear night, and gaze at the countless stars overhead, and realize that you are quite alone on a wide, wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean; and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends."- James S. Pitkin _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
