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Old 03-01-2012, 16:07   #1111
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Re: Long-Distance WiFi Device

Chester, make sure you rig a down haul on that bullet. Don't try and use the data cable. I broke our masthead rig getting a halyard wrapped on it. We are using a hoisted spare with a 9dbi omni that quite working well when the wind piped up today. When I checked it, it was like a dart in the wind! Once I secured the down haul we were back in business.

Have fun in the BVI!

George
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Old 03-01-2012, 16:09   #1112
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Re: Long-Distance WiFi Device

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Originally Posted by jcmoon View Post
Howdy, I have been looking at wifi booster systems and this one looks pretty interesting. I have tried radio Labs Wave RV and it does not work very well for us. It has very low power 200mw compared to this gadget. has anyone tried one of these?

We went with a completely different route.

Attachment 35543
Cellular Mifi

PLUS

Attachment 35544
Wilson Sleek Mifi booster

Works everywhere we've been and we can take the package with us when we travel without the boat.
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Old 03-01-2012, 18:59   #1113
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Re: Long-Distance WiFi Device

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Originally Posted by Seahunter View Post
Cellular Mifi
Works everywhere we've been and we can take the package with us when we travel without the boat.
Wow, the cellular data roaming costs must kill you. This costs thousands per month !

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Old 03-01-2012, 19:11   #1114
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Re: Long-Distance WiFi Device

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Wow, the cellular data roaming costs must kill you. This costs thousands per month !

cheers,
Nick.
Roaming charges, there ain't no stinkin' roaming charges.
Really. We stream Netflix, etc with 10Gb per month. You can get less if you want and can use any number of carriers; it's up to you. If we're out of range we use this, albeit not so inexpensive:

Attachment 35548
Iridium with WiFi
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Old 03-01-2012, 19:29   #1115
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Re: Long-Distance WiFi Device

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Originally Posted by djdeakyne View Post
. . . I think I get it, putting it on top of the mast has nothing to do with line of sight for range. It is only to avoid the dark spots created by other masts in the anchorage.

But, unless the hotspot is also elevated, won't the other masts will still be in the way as the line of sight points down to the beachfront bar? . . .
In most of the places I have been that have WiFi in the eastern Caribbean and Florida, the land station (like a marina) has their antennas up on the same antenna masts that they mount their VHF and other antennas. In other words the WiFi is quite high up off the ground.

But in any case shooting a line of sight down through the close in obstacles has a better probability of getting a good lock-on versus shooting a line of sight through a whole forest of obstacles (masts, sport fisherman rigs, buildings, etc.) Naturally it is the "metal" obstacles that can cause the problems although I have found in real life some good reduction in signal when shooting through FRG hulls.

Of course, swinging at anchor (you and others) can make reception intermittent at times, but still getting your antenna system up high seems to increase the probability of good solid signal lock-on.

And it also works the other way. In the outer anchorage off St Georges Grenada, there was a restaurant/bar up on a bit of a rise and their antenna was inside the building. I had to lower the antenna to get a straight line of sight shot up into antenna which was "covered" by their metal roof if I raised my antenna too high.
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Old 03-01-2012, 19:29   #1116
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Re: Long-Distance WiFi Device

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Originally Posted by djdeakyne View Post
HI Michael, Nice How-To on the cable.

I really don't understand all the infatuation with height. The VHF is high for line of sight to the horizon. The "6ft man sees a 6ft man at 6 miles" rule is plenty for the range we're talking about for wifi.

Yes, the antenna does need to be above the bimini and boom, but what is height really buying you. For a hotspot 300 meters away, the top of a 6 degree vertical beamwidth from a high gain omni antenna would still be 15 meters high. Much higher than most bars and coffee shops that I frequent.

I think the real problem is when a narrow beam pitches up and down, above and below the hotspot, the reception will be crappy. Lets face it, 6 degrees is not much for a boat to roll at anchor.

Cheers, Dave
The reason for height is two-fold - get above obstructions and above fresnel lensing effects. While masts, etc are small dimensional profiles, they reek havoc by disrupting signal polarization and causing multipath signals. The fresnel lensing problem is caused by ground interactions and is solved by mounting the antenna 8-20' (gain dependent) above the water.

So 8' or so is the minimum mounting height, and any higher is a choice dependent on the environment you will find yourself in most of the time - empty anchorages = no problems, full anchorages or lots of trees/houses = more problems.

And you don't have to worry about over-shooting close-in AP's. There are strong enough side lobes on all antennas to take care of that. Right now, my router is sitting 15' directly underneath my wifi radio and it shows the radio as a strong signal.

FWIW, our wifi radio is mounted 15' high on a pole on the back of our arch and we find this to be fine.

Mark
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Old 03-01-2012, 20:34   #1117
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Re: Long-Distance WiFi Device

"
And you don't have to worry about over-shooting close-in AP's. There are strong enough side lobes on all antennas to take care of that. Right now, my router is sitting 15' directly underneath my wifi radio and it shows the radio as a strong signal."

Same here. My antenna is 50 feet up and always the strongest signal.
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Old 03-01-2012, 22:38   #1118
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Re: Long-Distance WiFi Device

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Originally Posted by Seahunter View Post
Roaming charges, there ain't no stinkin' roaming charges.
Really. We stream Netflix, etc with 10Gb per month. You can get less if you want and can use any number of carriers; it's up to you. If we're out of range we use this, albeit not so inexpensive:

Attachment 35548
Iridium with WiFi
Huh? yes, now you are showing an Iridium phone, but I was replying to your post where you showed a Verizon MiFi with booster. As soon as you cross a border going outside the country where the cell contract is, you are going to pay thousands per month in roaming charges.

There are unlocked MiFi type of devices, which accept SIM cards from any carrier in any country. This works to keep costs in hand.

The Iridium link is crazy slow and expensive too.

cheers,
Nick.
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Old 03-01-2012, 23:55   #1119
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Re: Long-Distance WiFi Device

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Originally Posted by djdeakyne View Post
I think I get it, putting it on top of the mast has nothing to do with line of sight for range. It is only to avoid the dark spots created by other masts
It does indeed also have an affect on range and line of sight. Google 'near line of sight' for example. You can also look up 'fresnel zone' for another reason. Water absorbs, metal reflects wifi signals.

Quote:
Originally Posted by djdeakyne View Post
Also, we're talking about centimeter wavelengths and most mast thicknesses don't even approach that. Also, my house, or even the coffee shop wifi doesn't seem to have much trouble going through walls that are much thicker than a centimeter.
You'll recall that a few posts previous, it was mentioned that tin foil was being used as an attenuator... Pretty thin and very effecttive. Look inside most directional antennas and you will find 'tin foil' reflectors focusing the radiated energy. Wifi travels easily through dry materials such as cinder blocks, bricks and dry wall. Not so well through leafy trees (full of moisture). Bounces off metal like light off a mirror.

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Old 04-01-2012, 05:46   #1120
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Re: Long-Distance WiFi Device

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Hi! Not sure how this one slipped past me. I have a drawer full of components under my bunk now to make a like device. I can't load your video yet but I am looking forward to viewing it soon. Are you using an Arduino?

George
Hi George.

I'll post a link to more pics when I get back to the boat.
I used a Basic Stamp for the prototype. This one uses a Parallax Propeller because I wanted to fit the controller board inside the rotator.
The compass is an HMC6352 from Sparkfun (+/- 1 degree), and the DC motor is from ebay ($20).



Your Arduino would work just fine for a setup like Version1 that I had with the Stamp, but the board would be too big to put inside 1 1/4" PVC conduit. On that design, I used a string taped to the outside to tell me if I was twisting the wires inside.
Everything else is from Lowes/Home Depot. The rotating section is a PVC conduit expansion joint. The radios are back-to-back Nanostation and Picostation. I made the slip rings by sending the power and ground through skateboard bearings.
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Old 05-01-2012, 07:45   #1121
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Re: Long-Distance WiFi Device

Thanks all for all the great ideas. The reason I asked was to find out why putting wifi up a mast was necessary and if it would be worth my time.


After researching all the factors that you all proposed, I have tried to generally quantify these interferences and here's what I came up with:

The Fresnel Effect is the only thing that matters.

1. Antenna height helps for the purpose of fresnel zone ground interference. See LigoWave Link Calculator
Boat Hotspot Rx Signal (db)
14’ 5’ -77.90
14’ 12’ -71.48
14’ 20’ -68.39
60’ 20’ -68.37
So, as you can see, with my situation of a 14’ boat antenna, if the hotspot is sitting on a table on the beach (5’MSL) there is considerable degradation . If the hotspot is on a table in a bar on the dune (12’MSL) the signal would be better (-71.48db) and if the hotspot was at 20’MSL there is nothing gained by putting the antenna on top of the mast.



Fresnel Zone with 14'Tx 12'Rx



Fresnel Zone with 60'Tx 12'Rx
Paramaters: Georgetown, Exumas - 2.36 mile link, Tx Power 28db 12db antenna Rx antenna 3db Rx Sens -90db - Basically Nanostation on boat to Linksys on shore




2. Line of sight from the top of the mast is not necessary for 5 mile wifi.

3. Masts do cause scatter and absorption, but are insignificant
The 1st Fresnel Zone for a 1km link has a 5.6m diameter. This is a cigar shaped beam with a cross-sectional area of 117 sqft. Maximum blockage is 40%. Acceptable blockage is 20%. That much may be possible in a crowded marina (where they provide close wifi anyway), but that density just does not exist in anchorages. If there is truly a ‘forest of masts’, I’m looking for a different anchorage anyway.

So my conclusion is that if it makes you happy putting your antenna up the mast, do it, but you’re not gaining much except for a few rare situations but it needs to be above the boom.

Thanks for all your input.

Cheers, Dave
Sailing Vessel Tortuguita


references:
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Old 05-01-2012, 08:54   #1122
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Re: Long-Distance WiFi Device

Which is all very good information - theory and good engineering is always the best plae to start - but then when it is all done . . .

I take the antenna system and attach it to a halyard and a down-haul and start raising it up the mast while I try out each elevation in real life. Then put the antenna where it works best.

However, it you are actively cruising and moving from one location to another what I did was engineer a system that allows me to move the antenna system up and down in elevation and also fore and aft on the boat. Then I can put the antenna in the best position for the specific anchorage/marina/whatever where I happen to be.

Surprisingly enough - in the "old days" before WiFi cruisers tended to anchor away from each other both for privacy/noise and simply - it was more pleasant. But now with most everybody having WiFi and external antennas you will see a "forest" of masts all anchored in the "WiFi sweet spots" that each anchorage seems to have. The sweet spots are the result of mountains, houses, and other obstructions blocking the shore based AP.

Those cruisers without external antenna systems take their computer ashore to "internet cafes" or other "hotspots" and their boats have the rest of the beautiful anchorage to themselves.
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Old 05-01-2012, 11:02   #1123
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Re: Long-Distance WiFi Device

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Originally Posted by djdeakyne View Post
I used a Basic Stamp for the prototype. This one uses a Parallax Propeller because I wanted to fit the controller board inside the rotator.
The compass is an HMC6352 from Sparkfun (+/- 1 degree), and the DC motor is from ebay ($20).
Check out this link: Low Cost Sat TV



ciao!
Nick.
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Old 05-01-2012, 15:47   #1124
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Re: Long-Distance WiFi Device

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However, it you are actively cruising and moving from one location to another what I did was engineer a system that allows me to move the antenna system up and down in elevation and also fore and aft on the boat. Then I can put the antenna in the best position for the specific anchorage/marina/whatever where I happen to be.

Surprisingly enough - in the "old days" before WiFi cruisers tended to anchor away from each other both for privacy/noise and simply - it was more pleasant. But now with most everybody having WiFi and external antennas you will see a "forest" of masts all anchored in the "WiFi sweet spots" that each anchorage seems to have. The sweet spots are the result of mountains, houses, and other obstructions blocking the shore based AP.
In 'the days' when wifi meant using a PCMCIA Card, the only place to anchor was right in front of the bar. Now, with a halfway decent wifi setup, you should be able to anchor just about anywhere.

You antenna height shouldn't matter much but lower shouldn't be better.
What may be happening is that your omni antenna is tilting when you move it around and the radiation pattern is above or below the hotspot. Unless you have devised some way to keep it perfectly perpendicular to the horizon.
It doesn't take too much tilt too miss your AP when you have a vertical E-plane like this:
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Old 05-01-2012, 15:54   #1125
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Re: Long-Distance WiFi Device

Isn't this a good reason to use a lower gain (say 8dbi instead of 10 or 12) to get a wider vertical beam?

Where I'm at right now, at low tide my boat is about 6 feet lower than the main dock. then there is a bit of an incline up to the land dwellings... With a higher gain antenna mounted just above the boom, It seems like I would get fewer nearby networks, or spotty performance, because the 'beam' is too narrow reach 'up' over anything... for a boats motion at anchor it would be a similar situation. You rock one way, and the beam is pointing at the water, etc..

From what I'm hearing here, distance isn't the most important thing, and a wider vertical arc would solve most of the mentioned issues with being at anchor. Or am i missing something?
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