Antenna for WiFi

[jdoe71]

I just got one off eBay for 60 buks, it's a USB wireless adapter inside a can mounted on a tripod. Looks crude, works great. You don't need your internal adapter. This one is not too directional, probably gives about 120 degree coverage. We find it very useful indeed, and I'd just like to thank all those folks who just buy a wireless router and plug it in. thank you.

[Vasco]

Hellosailor,

This is getting better and better. One thing about the AP. I assume that it needs power to work, if it's attached to the antenna halfway up the mast how does it get power?

[hellosailor]

jdpoe-
Just remember, when you are connected to an open Wifi hub, unless you are using a VPN server of your own, EVERYTHING you transmit can be recorded by the folks running that hub. HTTPS pages are probably secure--but everything else can be read by them. And in any event--using a firewall to protect your own computer is a must. There are plenty of bad guys who KNOW where the open systems are, and they exploit innocent travelers using them.

Rick-
There are two ways to power an AP up the mast. One, is by running the power adapter alongside the ethernet cable.<G> Or if the AP runs on 12V, run ship's power up alongside the ethernet cable. But many of them now provide for "POE" meaning "Power over ethernet". The power adapter (or connection to 12V) is made down below, at your computer, and a "T" connection sends it up the ethernet cable on a normally unused wire pair.

From what I'm told, unless you really need the *height* of the antenna to clear local obstructions, you don't need an AP aloft. Simply putting a good high-powered PCMCIA card in the computer, and attaching a high-gain omnidirectional antenna to it, will come close to the performance.

The other solution of course is instead of using the AP, add an in-line bidirectional amplifier in the antenna cable. It's like a cigar tin or a big fountain pen, that screws inline into the antenna cable. Smaller and simpler than an AP, although it will cost a bit more.

[donradcliffe]

I'm happy with my Hawking HWU8DD --called a hi-gain USB dish adaptor. It's directional, but will allow the boat to swing back and forth 20-30 degrees at anchor. Bought it for about $60 with rebate.

Putting the antenna higher is better with weak signals, so we use a 6 ft USB extension and put it under the dodger when necessary. Longer extensions can cause problems.

[slomotion]

We met some people in the Bahamas who claimed good results with 2 directional antennas mounted on oppositite sides of their radar pole. The antennas connected to a twin antenna access point which was then connected by ethernet cable to a wireless router. That way the the laptop(s) remains mobile and does need an etherent cable or wired connection to the antenna.

Not sure I followed hellosailor's remark about using a VPN server, but these are trivially easy to set up - just don't see how that protects you if you are connecting to an unsecured wireless network, unless you have a remote server which is connected to the Internet in some other manner. IE. I can use my laptop to connect to a wifi hot spot and then establish a VPN connection to my home server. That way my wireless communication is encrypted through the VPN tunnel and uses the server's connection to access Internet sites.

[cferger]

An external omnidirectional antenna with a usb adaptor will work fine. My company provided laptop has an internal wifi adaptor and antenna, but simply does not work. When I need to access our corporate network from home via ivpn, i just connect an external usb antenna and it works fine.

[cjenkins]

I'm going to need something like this soon. Someone mentioned "hoisting it up the mast if/when you need it." I had been thinking that anything up the mast would need to be permanently mounted and had not considered the possibility of a moveable antenna arrangement. If any of you have used that system, how did you like it? How do you keep it from banging against the mast? Could you hoist it up to one of the spreaders (whichever side is facing the likely source of a signal)?

Charlie

[slomotion]

I think hellosailor's point was simply that so called 'standalone' USB wifi antennas are really an integrated USB wireless adapter + antenna. There are some 'pure' USB antennas which require a wired connection to a separate PC card. However, there are few cards that support an external antenna connection - some others (both PC card and USB) can be dissected to allow soldering an external connection. Under no circumstances should you open a laptop and attempt to solder an external connection to the laptop's internal wifi circuit - even serious wardrivers do not risk this.

[W32PAMELA]

An "AP" is what we want to connect to for WiFi access. 2 AP's cannot communicate with each other. Most AP's can also be set to act as a client device which can connect to an AP. AP's are frequently refered to as "wireless routers".

All PCMCIA cards, USB wifi adapters and laptop internal wifi adapters (mini-pci cards) are client devices. Client devices operating in the "infrastructure mode" can connect to an AP. Client devices operating in the "adhoc" mode can connect to another client device that is set to "adhoc".

I like to call the pcmcia card, usb adapter, mini-pci card adapter devices computer based because they all require special drivers and a utility program installed on your computer for them to operate. XP provides a basic utility program to operate your wireless device but generally the program provided by the device manufacturer will provide more functionality.

AP/Client Bridges are ethernet based devices. They require no special software or drivers to be installed on your computer. They are actually basic computers running either a proprietary OS provide by the manufacturer or a third party OS frequently based on Linux. Because an ethernet based device operates independant of your computer, they can be used with both Mac's and PC's. The OS in your device (firmware) controls what functions your device has and how easy it is to use the device in a particular configuration. Most AP/Client bridges are sold to be used mainly as an AP and the software that allows it to be used as a client device can be very cumbersum. On the other end of the spectrum are devices that are intended to be provided to subscribers of private WiFi networks. These usually have easy to use software, are more powerful and have better receive sensitivity than most retail AP/Client bridges.

I prefer the use of a USB device or ethernet device onboard. In any case the amount of coax used between the device and the antenna should be kept short as possible, less than a meter. PCMCIA cards always require too long a run of coax to the antenna. The connection point on the card is usually one of the more fragile types making mechanical failure likely from frequent connecting and disconnecting. If you have to use a PCMCIA card try to get one with an SMA jack rather than MMCX or U.fl. As mentioned in hellosailor's post, losses in the cable can be made up by using a bi directional amplifier but this adds another level of complexity to the system and considerable extra cost. If you are considering a system with an amp be sure and check the maximum input power the amp can tolerate. Many can only handle 50-100 mw.

When comparing wifi devices you need to consider both the output power and the receive sensitivity. Most of the time the only advertised statistic is the output power. A wifi connection requires 2 devices to talk to each other. They both have to hear and be heard. If you're anchored 200 yards off the beach, the crew has gone ashore in the dinghy to play volleyball and didn't take a VHF and you need to know what they did with the cork screw, you'll be able to get their attention with the loud hailer on your VHF if you have one but you won't be able hear their response to the question. High output power will allow you to be heard by the device ashore but that device onshore may only be putting out 30-50 mw and if you don't have adequate receive sensitivity you won't connect.

Hellosailor also raised a good point concerning the fact that wifi connections that aren't encrypted are recordable. Even some of the encryption schemes are easily broken. Most access points can log all of the url's you visit. To avoid having your transmission read over the air you can use a "hotspot VPN" these are commercially available for a monthly fee or you can use one of the free ones. Software installed on your computer encrypts all your over-the-air transmissions. The encrypted transmissions are sent over the internet to a VPN server which decrypts the information and routes it back into the internet to the address you intended. I use the AnchorFree Hotspot Shield when I want privacy. This is one of the free services and it generally works ok although it can sometimes slow things down. I think the server gets overloaded.

[slomotion]

Well, I don't want to quibble about the precise definitions of "AP", "bridge", and "router" because many devices are multifunctional, but these statements are mutually exclusive:

"2 AP's cannot communicate with each other. Most AP's can also be set to act as a client device which can connect to an AP."

One of the most common uses of APs is to extend the range of wireless networks by having multiple APs which communicate with eachother. Also, I don't find, for example, DD-WRT to be particularly "cumbersum" (sp).

[hellosailor]

Slomotion-
Directional gain antennas are great at what they do. There are also "stacked" or colinear coaxial antennas, which can work very, and would allow them to use one single stick (maybe in inch thick) instead of two dishes. And--not have the blind spots off the edges that the two dishes would have. There are many ways to make a "better" antenna, if using twin directional antennas back to back makes them happy...fine by me.

"I think hellosailor's point was simply that so called 'standalone' USB wifi antennas are really an integrated USB wireless adapter + antenna." Precisely. While a USB port could be used as a power supply for an amplified antenna...I've never heard of doing it that way. And, the antenna would still need to be plugged into some wireless networking card, not just the USB power source. Which is why I say...

Cf-
"external usb antenna" Think of it this way. If someone at the marine store keep trying to sell you "new ropes for that pole thing in the middle of the boat" would you cringe a bit? That's how "usb antenna" sounds. There's no such thing, the USB bus is a data bus, it cannot and does not carry radio frequency signals. It is not an antenna. All that you can do is connect a complete external USB Wifi card to the USB bus. Whether some clever folks have hidden that gizmo in what they call an "antenna", or not, doesn't affect what it really is. Calling it an "antenna" is dumbing it down and underselling it

Charlie-
I think I mentioned hoisting it up and down the mast. You certainly could use an external antenna with, say, a 6 foot cable, belowdecks, and if you need more gain (from line of sight) hoist it up the halyard on a 50' cable instead. Or, use an AP and hoist it...whatever...so the Wifi rig was only aloft when you were in port.

Pamela makes some good points--there is lots of confusion about nomenclature, partly from devices that combine multiple functions, partly from maufacturers who don't want to use technical terms like "mast" or "mainsail".<G>

"The connection point on the card is usually one of the more fragile types making mechanical failure likely from frequent connecting and disconnecting. If you have to use a PCMCIA card try to get one with an SMA jack rather than MMCX or U.fl." Sadly, the typical snap-in connection like an MMCX is actually rated for some ridiculous number like 100 uses. If you use one--plug it in and leave it plugged in! Or get a "pigtail" which has the MMCX connector at one end, and 6" away has a better conector like SMA, which won't wear out the same way. Then get an antenna to match the SMA or whatever the pigtail ends in.
"Hellosailor also raised a good point concerning the fact that wifi connections that aren't encrypted are recordable. Even some of the encryption schemes are easily broken." Yup. Folks don't realize how insecure most Wifi is. WEP encryption can be broken in 3-5 minutes. WPA is pretty good, but in these days of identity theft it pays to be paranoid. If I'm logged in from an airport wifi access, I may read email and visit forums or newspapers--but I'll never do online banking, even though it uses HTTPS and is supposed to be secure. One day, that too will be hacked. I just need it badly enough to want to be the poster boy for the first hack of it.

[slomotion]

hellosailor,

Gotcha - the system that we 'heard' about, but did not see in action, had twin powered 15 dBi antennas plus a powered AP plus a powered router. Obviously, you want to turn this system OFF when not in use. They claimed to have 'reasonable' Internet access 1+ mile off shore when we had trouble with 300'. Don't know the brand or specs of directional antennas they were using.

[W32PAMELA]

Slomotion:
"Well, I don't want to quibble about the precise definitions of "AP", "bridge", and "router" because many devices are multifunctional, but these statements are mutually exclusive:

"2 AP's cannot communicate with each other. Most AP's can also be set to act as a client device which can connect to an AP.""

It's not an AP when it is acting as a client device.

"One of the most common uses of APs is to extend the range of wireless networks by having multiple APs which communicate with eachother. Also, I don't find, for example, DD-WRT to be particularly "cumbersum" (sp)."

When you extend the range of a wireless network you are placing the AP in a different mode to allow communication (bridge, WDS etc). It's not an AP any more.

DD-wrt is a good firmware but if you compare the browser interface to one used in a client subscriber device it looks complicated if not cumbersome (used spelling check this time) to a new user. I use DD-wrt in my router and it's great but some AP/client bridge/wireless routers are a pain to use if you want to easily change from one AP to another. Rather than simply allowing you to scan for available AP's and choose one from a list to connect to, you have to do a scan on one browser page to see what's available, then go to another page to enter the name of the AP along with other information then try to connect while not knowing if the AP is secure or not. That can be cumbersome.

[slomotion]

Well, if you buy a device called an "access point" and like most such devices it has these other capabilities, then well ....... OK, it's a definitions quibble and we are both right.

MCSE, MCSA, MCP+I, MVP (Windows Networking)

[hellosailor]

slomotion-
One mile is nothing. I think the current record stands at 125 miles for line-of-sight WiFi, there's an annual shootout vaguely around Vegas every year. Of course, to get that distance the team was using a 12-foot dish, and getting "line of sight" by erecting it on a mountain.<G>

Unfortunately, unless you are a real techie or in the military/government market, everything about "communications gear" today is "What color would you like?" "We've got a smaller one!" and "Would you like fries with that?"

Ask a cellular company where the nearest tower is (to find out if they serve your area) and they get all paranoid and assume you must be intending to steal it or blow it up. They'll never tell you. Most of the ISPs and Wifi vendors act just about as nicely.