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**David M** · 31-01-2012, 08:46

I have a powerboat with a 10 foot mast that I would like to mount a high gain WiFi antenna to. A large whip antenna would work fine. I am looking for coax that would have the minimal amount of loss and a router that has a coax connector that is compatible with the coax connector.

The WiFi will only be used when the boat is tied up, therefore a narrow vertical beam angle will not be a factor. The antenna does need to be omnidirectional because being up on mast, I will not be able to point it. I will be getting a cellular modem for underway use. WiFi at the marinas I visit is usually free.

I am open to ideas and any links to Amazon, Fry's, Newegg or any other electronics store would be most appreciated.

This 15db antenna with a 30 degree vertical beam angle looked interesting...
http://hawkingtech.com/index.php/pro.../hao15sip.html But I am certainly open to other ideas.

AnchorageGuy · 31-01-2012, 11:53

David, I don't know that I have ever seen a "whip" wifi antenna. They tend to be short, maybe 18" and connecting an antenna to a router with coax is a bad idea. Anything over a foot or two will give you too much signal loss. As you know the Wifi discussion on the board has been going on for some time with a ton of good recommendations. The best combination is a bullett 2HP connected to a 9db omni directional, connected to either your computer or a router with a Cat5 cable. We like the Engenious 9db antenna and are using a Cradlepoint router. A Google search for either of these will give you lots of sources at a variety of prices. Chuck

SoonerSailor · 31-01-2012, 13:03

At Wireless B/G frequencies of 2400 mHz, a 50 ft run of Times LMR400 would lose only 3.15 dB according to my Linecalc app assuming a proper impedance match. That doesnt seem too bad to me. The OP would probably have a much shorter run than that and so less loss. Cant direct you to a specific product, maybe others can.

Chip

hellosailor · 31-01-2012, 13:09

At ten feet, DOCKED, I'd just hoist the router aloft in a plastic bag or tupperware container, a bit oversize to let the heat transfer better. Okay, that's not elegant, but it sure meets the "cheap and simple" requirement. Ten feet...no big deal. And if the router has an external antenna, odds are you can unscrew it and add on something like a 6db gain omni that uses only about a foot of cord for minimal loss. Again, just hoist the whole thing.

AnchorageGuy · 31-01-2012, 13:29

LMR 400 will loose about 1/2 db per foot and this does not include connection which will add to the signal loss. That is under ideal conditions. With a 10 foot mast it is highly doubtful that the computer will be sitting at the bottom of the mast. The point being that there are better connection methods than coax. A wifi adapter with an active USB cable will even have less signal loss and as hellosailor stated can be hoisted higher when needed . Here is a system we have used for years and pick up signals miles away.
The Trawler Beach House: Simple and Inexpensive WiFi
The Trawler Beach House: WiFi Adapter For The Boat Revisited

This system has worked and was still working until recently when we switched to the Bullett using the same antenna and our second mounting system. We switched only to try the Bullet to see if we saw any significant improvement. To date we have not picked up any more APs than we did with the older system. We have used this extensively while cruising all over the eastern US and western Caribbean. Chuck

St. Elsewhere · 31-01-2012, 13:30

I am not a WiFi expert.

My system has an antenna on top of the boat, a "bridge" connected to the antenna by coax, and then a router connected to the bridge via Cat 5 wire, and then computer/s plugged into the router also with Cat 5 wire.

My understanding is that the bridge is a radio transceiver that is needed for the long range WiFi link. It also has software that provides for identifying available networks, and configuring the bridge to connect to a selected network.

Here is a link to one such bridge: Client Bridge and Access Point Combo

christian.kautz · 31-01-2012, 13:32

Quote:

Originally Posted by hellosailor

At ten feet, DOCKED, I'd just hoist the router aloft in a plastic bag or tupperware container, ......

the best way by far, even if u add hundreds of feet CAT5 ;-)

SoonerSailor · 31-01-2012, 15:06

Quote:

Originally Posted by Waterwayguy

LMR 400 will loose about 1/2 db per foot and this does not include connection which will add to the signal loss. That is under ideal conditions.

Chuck -

All of my sources, including Times Microwave themselves, give a matched loss of 6.6 dB per 100 feet at 2.4 gHz for LMR-400. Even little old RG8X has a matched loss of only about .26 db per foot. What is your data source?

As for the rest of it, I agree completely. Connectors will add some loss, and an imperfect impedance match will add more. It is certainly best from the signal strength point of view to avoid long coax runs, but 10 or 15 feet of the right coax is not going to hurt you much. There is more than one way to skin this cat, his installation needs will dictate the best solution.

Chip

ka4wja · 31-01-2012, 15:26

David,
I'm hesitant to reply here, as I don't wish to get involved in a long winding thread......but here are few quick facts that might help you...along with one opinion....

1) a 15dbi gain omni antenna will probably have a vertical beam width narrower than 30 degrees, so you'll need to take extra care to make sure you've got it vertical.....
But even so a Wi-Fi antenna marketed as a "12db" or "15db" should work fine for your application.....

Quote:

Originally Posted by David M

This 15db antenna with a 30 degree vertical beam angle looked interesting...
http://hawkingtech.com/index.php/pro.../hao15sip.html But I am certainly open to other ideas.

2) Although I'm partial to Davis RF "Bury-Flex" (which is a LMR-400 UF variant), you can get the loss figures for all the Times Microwave cazbles here....
Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator

And, as you can see at 2450mhz, a 10 foot length of LMR-400 would have a loss of about 0.7db...and LMR-400UF (ultra-flex) would be 0.8db loss for a 10 foot legth at 2450mhz....

3) And, now here's an opinion.....
Bite the bullet and buy a Bullet2HP, attach a 12 - 15db gain omin antenna, and run a Cat 5 cable inside to a small wi-fi router...and you'll find life to be much happier!!!!
I did this and have been very happy!!!!

I hope this helps....

Fair winds...

John
s/v Annie Laurie

**s/v Jedi** · 31-01-2012, 15:33

Simply:

- Ban coax.

- Get a BulletM2 instead of Bullet2hp

ciao!
Nick.

**bstreep** · 31-01-2012, 15:55

I'd agree with the above - go Cat5 rather than coax. Give Bob a call at islandtimepc.com.

LeaseOnLife · 31-01-2012, 16:03

Simply....

I fully agree with pointing towards a Bullet 2HP or 2M, this is our setup here. We also use a Nanostation where directional antennas work.

But lets make sure the OP, and others, understand the parts needed to make the Ubiquity Bullet work.

* Omni-directional antenna without down-tilt, coupled directly to the Bullet, I prefer 9db over 12db, on a monohull
* the Bullet device
* a way to mount or hoist the Bullet
* Ethernet cable to reach from Bullet to POE injector
* POE, power over ethernet injector. The bullet seems to like more than 12V, especially for long ethernet cable runs.
* If you are powering from 12V you probably need a DC/DC converter 12V to 18v with proper connectors. There is a POE injector with built-in DC/DC converter from Tycon, just ordered one, don't know how well they work.
* Ethernet cable from POE injector to PC/Mac or router
* Knowledge, time, interest, to configure all above

I am sure I forgot a few things, but this is a start.

Cheers

Dirk