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Old 16-07-2010, 13:05   #1
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Wifi 'Antenna' Question

I'm mindful that there are other threads on this topic (which I've reviewed), but what I'm hoping is that someone can provide me with a quick primer on what the specifications mean and what I should be watching for...

What I'm looking for is a more or less plug-and-play USB wifi "antenna" to boost the send/receive range of my on-board PC. Range and power are paramount. I won't be mounting anything permanently - ideally, I'll run a reasonably short (< 15ft) USB cable either out a porthole or up the companionway and just sit (perhaps suction-cup) the antenna on the cabin top. The antenna will need to be omnidirectional, as we may swing through a full 360 degrees.

I know technology is always a series of compromises, but for an omni-directional antenna mounted approximately 9ft above the water, what specifications are optimal? Should I be looking for a low-gain antenna? What is "low"? Wattage (more is better, or is it more complicated than that)?

Specific manufacturer recommendations are welcome, but what I'm really looking for is a better understanding of the various specs so that I can determine what I need and be comparing apples to apples.

Thanks in advance!
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Old 16-07-2010, 13:31   #2
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Work great.

Alpha 500 now 1000mW USB WiFi Booster AWUS036H RPSMA - eBay (item 140372205163 end time Aug-03-10 14:33:38 PDT)
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Old 16-07-2010, 14:10   #3
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You will need a WiFi adapter and not just an antenna. You can connect an antenna to an adapter. If this is indeed a USB then most likely you will have to use an "active" USB cable for 15 feet. We have use the Engeniuos for years and are very happy with it.
http://tinyurl.com/dcam3r
You can of course use this without the external antenna but you will reduce the range.
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Old 16-07-2010, 14:13   #4
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Many thanks - perfect! I'll re-post once I've rigged something and let you know how it works. Cheers.
Rob
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Old 16-07-2010, 14:22   #5
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We have done some slight modifications since the first unit.
http://tinyurl.com/m9gg8z
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Old 16-07-2010, 15:38   #6
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Very slick indeed, Waterwayguy - looks like it belongs there. I have an idea as to how to create a flexible mounting option, but I'll wait to see whether I can pull it off before I share...

Cheers,
Rob
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Old 16-07-2010, 16:43   #7
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Marine Wi-Fi - Budget Marine

comes with an installation cd and I gotta say the thing works great....not cheap but lasted ages and works well!
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Old 16-07-2010, 19:55   #8
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The Ubiquiti WiFiStation-EXT is probably the newest Usb device on the market. I haven't tried one yet but they look like they are a good option for the price. They come in a water resistant case with a 16 foot USB cable.
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Old 16-07-2010, 20:12   #9
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3G is the way to go. The WiFi channels are too crowded. The better antenna simply picks up more noise and interference. Your only hope is an antenna that is somewhat horizontally directional to reject unwanted stations. But that's a problem at anchor. Your results may vary.

3G will work 'almost continuously' a few miles offshore from BC to Panama.
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Old 17-07-2010, 09:58   #10
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External Wi-Fi Modem/Radio

Quote:
Originally Posted by RSMacG View Post
What I'm looking for is a more or less plug-and-play USB wifi "antenna" to boost the send/receive range of my on-board PC. Range and power are paramount. I won't be mounting anything permanently - ideally, I'll run a reasonably short (< 15ft) USB cable either out a porthole or up the companionway and just sit (perhaps suction-cup) the antenna on the cabin top. The antenna will need to be omnidirectional, as we may swing through a full 360 degrees.

I know technology is always a series of compromises, but for an omni-directional antenna mounted approximately 9ft above the water, what specifications are optimal? Should I be looking for a low-gain antenna? What is "low"? Wattage (more is better, or is it more complicated than that)?
RS,
You've asked some pointed questions, and here are some answers....

1) What you want (as others have posted) is not a wi-fi "antenna" but rather an external wi-fi modem WITH its own antenna....


2) Although I'm partial to my own set-up, but would probably use a Bullet 2HP in the future.......for YOUR application (portable, not permanently mounted. plug-n-play USB unit), I'd recommend the new Alfa unit.....(see below for specifics)....and two antennas, one short one (~ 3db) for normal use, and one longer one (6-9db) for times when you may need longer range....
Total cost here, including a long USB cable and extra antenna, is going to less than $50.....


3) I spent over a year using, and experimenting with a couple different wi-fi set-ups (both on board and on shore)......and like Chuck, in the end I opted for a more robust and weather proof "semi-permanent" solution.....
I wrote a long article about wi-fi, and my year long experiments, as well as detailed my entire set-up, with lots of photos.....
See here:
Wi-Fi

Please understand that while electronics is my profession, I'm NOT an IT guy, and I did NOT delve into minute details of different systems, but kept my explanations in the layperson to "light technical" genre.....


4) As for what "specs" to look for.....

a) Use an antenna with 3db to 9db of gain.......(short 3db antennas are nice for ease of portability, and 8-9db gain antennas are the max that you'll find "usable" for portable and/or "hanging from a halyard" operation..)

b) USB-based Wi-Fi units are spec'd by their power output (current max is 2watts/2000mW, with typical units being 1/2watt/500mW to 1watt/1000mW)......
And their receiver sensitivity, based on speed/thru-put (meaning the slower the speed, the more "sensitive" the receiver operates...)

Here are a couple of examples:
Quote:
Transmitter Output PowerManufacturer's specification is 2000mWReceive Sensitivity
802.11b: -92dBm
802.11g: -76dBm

Quote:
Transmitter Output Power1000mWReceive Sensitivity
for 802.11g
54Mpbs(64QAM): -76dbm
48Mbps (64QAM): -71dbm
36Mpbs (16QAM): -78dbm
24Mbps (16QAM): -80dbm
18Mbps (QPSK): -81dbm
12Mpbs (QPSK): -82dbm
9Mbps (BPSK): -85dbm
6Mbps (BPSK): -91dbm


c) Assuming that you don't want to spend a lot of $$$, please have a look on-line, for companies that specialize in low-cost and easy-use wi-fi networks and systems......you'll not find much at Best Buy, or computer stores.....
The guys I've found that are VERY knowledgeable and VERY honest, are the guys at Data-Alliance Data Alliance: Long-Distance Wireless Networking Equipment & Support
And, in addition to making sure that everything you're ordering will work together properly, they've got VERY low prices as well.....
(This point is important.....as some stuff you buy on-line is crap, and some of it just doesn't play well together.....trust me I learned the hard way!!!)

d) As for specific units, try the new Alfa unit......
See here:
Alfa AWUS036NH 2000mW Best Long Range USB Wireless Adapter. 802.11N/G/B. w/Jack & Antenna
or here:
Alfa AWUS036H 1000mW USB Wireless WiFi Adapter + Antenna. Long-Range. Upgrade from 500mW (this is the one I'm using)

For more units, antennas, etc.....surf the data alliance website.....including their technical info section, etc. and you'll learn a lot...



I do hope this helps....


John'
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Old 17-07-2010, 10:08   #11
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Quote:
Originally Posted by W32PAMELA View Post
The Ubiquiti WiFiStation-EXT is probably the newest Usb device on the market. I haven't tried one yet but they look like they are a good option for the price. They come in a water resistant case with a 16 foot USB cable.
Wow, Bob, this looks like a nice unit.....good specs, etc. and cheap....
When you test one out, please keep us informed....


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Old 17-07-2010, 11:46   #12
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The wifi spec (802.11a/g) already claims up to 100 meters distance......what exactly does this do?
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Old 18-07-2010, 08:10   #13
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The Alfa 500 mw with an Engenius 2408 omni on a 15 ft. usb works well for me,for longer range I also use the 5 mile wifi,(up to 7 or 8 miles offshore).Otherwise 3G is the way to go.
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Old 18-07-2010, 08:15   #14
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Quote:
Originally Posted by highseas View Post
The Alfa 500 mw with an Engenius 2408 omni on a 15 ft. usb works well for me,for longer range I also use the 5 mile wifi,(up to 7 or 8 miles offshore).Otherwise 3G is the way to go.
I would be very, very, very surprised if the 5 Mile picked up WiFi signals 7 to 8 miles away. Chuck
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Old 18-07-2010, 12:03   #15
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Alpha Networks makes a 2Watt one (USB), then you run a coax to the external antenna (directional - if in port, but omni - if at anchor).

The whole package is about 50 USD for the USB stick and probably another 50 for a decent antenna. The cable is cheap.

You can take a less powerful one and rig it with a wifi booster, but the boosters we found were all pretty expensive.

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