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View Poll Results: Where to mount the WiFi antenna?
Backstay 2 28.57%
Spreader 5 71.43%
Voters: 7. You may not vote on this poll

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Old 05-06-2011, 20:08   #1
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WiFi antenna location????

OK, so I just took delivery of one of Island PC's WiFi antenna booster thingums. I was originally going to put the antenna on the backstay with a self designed mount. But then in a momentary bout of lucidity, I looked at the chain plate running down the inside of the hull right next to the nav station. EUREKA!

Now I'm thinking about a wire through hull fitting at the deck by the shroud... zip tie the wire to the stay, and mount the WiFi antenna on the top spreader.

What say you? Backstay or spreader?
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Old 05-06-2011, 20:14   #2
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Re: WiFi antenna location????

I go with spreader.
In practice, the higher the better imho.

There have been discussions about height and theoretically being out of a signal's pattern, but mine's at the masthead and I can pick up my own boat's local area network every time. It's almost straight down from the mast!

Whether or not a source is close by or several miles away, I've been able to pick them up well with the antenna/transmitter/receiver 50 feet above the water.

Mounted on the backstay might induce twisting back and forth in wind.
Not necessarily bad for reception, but not desirable either.
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Old 05-06-2011, 20:20   #3
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Re: WiFi antenna location????

There are commercial backstay mounts... just with your concern in mind I tried to twist the backstay, and it is surprisingly rigid. The reason I was not going top of the mast was that I have the cellular and VHF antennas already there. the Cell is awful close to WiFi freqs and with only 6" separation, I was worried about interference. The top spreader is about 8 feet below the top of the mast, so like 36 feet above the water.
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Old 13-06-2011, 21:09   #4
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Re: WiFi antenna location????

One thing to add to this is that the longer the coax cable you run from the antenna, the more signal you will loose. Idealy, the cable should be kept as short as possible. Therefore, the extra height may be a false ecconomy.

I would trial fit both before making the final decision. Temporarily mount the antenna on the spreader, with the cable just passed through a window or something, see how much you can pick up and how strong. Then do the same with it on the b/stay and compare.

Before you jump up, I KNOW the cable length will be the same in both cases BUT, if the b/stay results are the same or only slightly worse then you can be assured they'll be as good or better once the cable has been shortened with the final instal.
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Old 13-06-2011, 21:13   #5
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Re: WiFi antenna location????

coachhouse roof is better yet---is right there. doesnt need to be elevated, as the directions on my old one stated--lol---and wire is short. but the poll had not this option.
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Old 13-06-2011, 21:34   #6
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Re: WiFi antenna location????

Quote:
Originally Posted by simonmd View Post
One thing to add to this is that the longer the coax cable you run from the antenna, the more signal you will loose. Idealy, the cable should be kept as short as possible. Therefore, the extra height may be a false ecconomy.

I would trial fit both before making the final decision. Temporarily mount the antenna on the spreader, with the cable just passed through a window or something, see how much you can pick up and how strong. Then do the same with it on the b/stay and compare.

Before you jump up, I KNOW the cable length will be the same in both cases BUT, if the b/stay results are the same or only slightly worse then you can be assured they'll be as good or better once the cable has been shortened with the final instal.
AFAICT, the unit the PO purchased has the radio hard connected to the antenna. The cable runs power and ethernet, not RF. Length to the spreader shouldn't be a problem.
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Old 13-06-2011, 22:13   #7
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Re: WiFi antenna location????

Masthead
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Old 13-06-2011, 23:06   #8
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Re: WiFi antenna location????

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Originally Posted by Unicorn Dreams View Post
Masthead
I second masthead, that is IF you are talking transmitter+antenna and not a coax extension. I have an all-in-one EnGenius on the masthead and it works great. At WiFi frequencies, extending the antenna from the main unit even a couple feet will result in noticeable signal loss and degradation of performance, no matter what sorta "boost" devices you use.
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Old 13-06-2011, 23:26   #9
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Re: WiFi antenna location????

Zip-tie to the stay, or shroud?. Only if you are permanently aground. Wrong in so many ways...
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Old 14-06-2011, 00:28   #10
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Re: WiFi antenna location????

set up many ISP's in the Caribbean over the years.
always had complaints from sailboats regarding signal strength even though the signal
was usable from up to a mile away via dinghy. Issues were usually antenna placement and the occasional "dead" zone. (yes they occur despite the denials, always conducted a signal survey when setting up a commercial wifi ISP so we knew where they were).

1. In a sailboat salon, which is usually at or below water line it is just not going to work.
My multiwatt transmitters can beacon you but your 17mW return signal just doesn't reach from virtually underwater. I even ran receive amps but without a decent antenna and some kick it just isn't reliable. Thus, the need for external amps and antennas.

2. I have used Linksys routers with DDWRT firmware in repeater mode for ages. They are cheap, reliable, will put out up to 250mW in native mode, and will repeat the signal so all you have to do is set the bloody thing somewhere with a clear view of the ISP and it will translate their wireless signal onto your own private wireless net. All it needs is a 12Volt power wire. NO ether cables or coax.
I had one survive for 3 years in a plastic bag on the boom in south america.
I have run them up the mast on a halyard.
I have even placed them ashore in a vehicle parked between the ISP and my boat.
This works because the DDWRT firmware will also "daisy chain" so a friend on a boat with better reception can act as a repeater for you. The DDWRT 54GL (available from walmart by special order, $50) also has external antenna connectors so you can
add a beam or omni external for a few more dB gain.

3. It is amazing what will interfere with a wifi signal. I have noticed substantial differences in signal level just by moving the antenna from inside the shrouds to outside the shrouds at the same height and heading. Some folks had great results putting the wireless device in a cheap chinese colander and making a beam out of it.
My experience has been if you can't see the antenna without obstruction, including
even a shroud wire, then sooner or later you will have problems in fringe areas.

The other thing to consider is most good wifi coverage is in mooring fields or relatively
dense anchorages. That masthead mount is above both your own boats interference and most of your neighbors. The spreaders not so well. Your own mast and a row of 50 others may be in the way along with the grounded shrouds of all those other boats. (or wait till that steel trawler anchors next to you and blanks you entirely till
the wind shifts).

If you decide to go low, i use a 120 degree beam antenna. Its not as sensitive to swing as a tighter 15 degree but still gives you some gain and the ability to aim through some of the interference. However, it is a pain in the backside if you swing a lot.

And i second the imho of coax up the mast is a loser. Yes, it works, but it is so much
more expensive and doesn't work near as well as a power over ethernet solution or
a repeater like i recommend to my customers. And coax insulation degrades with moisture. Particularly at these frequencies. Yes I know, the manufacturer guarantees their coax won't absorb moisture. File that with the government is here to help, the check is in the mail, and the 100 mpg carburetors.

cheers

gello
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Old 21-06-2011, 04:55   #11
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Re: WiFi antenna location????

Well, I went with the first spreader...about 24' off the water. Best so far was six miles! Guess it works. Thanks for y'alls input!
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Old 21-06-2011, 08:48   #12
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Re: WiFi antenna location????

wow, guess you showed us.
6 miles, geeeezzzz.
I only used to get that with multiwatt transmitters, receive amps, and
tightly aimed beam antennas when we were using wifi as cheap microwave like repeaters.

my best experience was 3 miles with
ISP station: a 15 degree beam, 1 watt of transmit power, a receive amp, antenna elevation 50 feet above water. No obstructions and total signal path over water.

Receive station:
.1 watt transmit, omni antenna, antenna height 15 feet and completely
visible to the beam antenna.

and that was a pretty sketchy in and out signal.

I never used more than 2 watts of tx power. With my license i could purchase up to 35 watts but that was just too damn dangerous to have around civilians. Don't want to cause cataracts or boil the brains of the poor guy cleaning the windows.

How did you manage 6 miles and what kind of contact was it?
More than just a beacon?

cheers

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