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Old 26-04-2010, 02:55   #1
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Antenna Mounting Question

Thanks to great advice received here, I now understand that neither my new WiFi antenna nor my GSM/UMTS cell phone antenna needs to be at the masthead, 75 feet above the water with attendent long cable runs, more weight aloft, and other disadvantages.

My first thought was to mount all this gear (plus GPS antenna, satphone antenna, and Navtex anntenna which are presently cluttering up the stern rail) on a pole.

I remember seeing an Oyster which had a pole approximately 2.5 meters high with a ring on the top of it, where all kinds of anntennae were living.

But I can't find any such thing. The Scanstrut poles and all that ilk are made for radar domes or satellite TV domes, and antenna mounting is an afterthought. In fact there seems to be provision for at most two other antennae on most of them.

Since my radar dome is already up on the mast, and I have no plans ever to have satellite TV, it seems a bit like the tail wagging to dog to buy a radar pole to mount my WiFi and GSM antennae.

Yet hours of Googling have failed to uncover any kind of pole like the one I saw on that Oyster.

Any of you guys faced the same problem, or have any ideas?

I would also mount these antennae on the mast, but lower down, if there were some way to do this.

Ideas?
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Old 26-04-2010, 04:49   #2
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Not a great photo, but here is the antenna mast I saw on that Oyster:

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It seems to be just a stainless pipe, mounted to the deck and well braced to the pushpit, with various antennae mounted to a stainless hoop at the top. I suppose I could have something like that fabricated.
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Old 26-04-2010, 07:51   #3
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Quote:
Originally Posted by Dockhead View Post

"Yet hours of Googling have failed to uncover any kind of pole like the one I saw on that Oyster."

That pole could be custom made. Frequently cheaper than you might think.


"I would also mount these antennae on the mast, but lower down, if there were some way to do this."
There's always a way. What about mounting them on the spreaders?
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Old 26-04-2010, 08:20   #4
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There's always a way. What about mounting them on the spreaders?
Yes, that was my question. First spreader would be a good place, or maybe even mount them to the radar dome guard. But I've never seen an antenna mounted that way -- anyone try it? Does the mast interfere with the antennae?
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Old 26-04-2010, 08:43   #5
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That's my mast (purdy, ain't it?):

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Any place for a couple of antennae there someplace? What do you guys think?

I can kind of imagine bolting a strut to the radome bracket, between the radome and the mast, and mounting one antenna on either end of that strut. Hmmm. Might make a mess out of a spinnaker halyard, though. Maybe on the spreader itself?
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Old 26-04-2010, 08:59   #6
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I've got my AIS antenna mounted on the top spreader and it seems to work very well. No doubt the proximity to the mast and shrouds has some effect on the antenna pattern, but I don't think it's too significant.

On other boats I've seen GPS and satphone antennas mounted on the spreaders.
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Old 26-04-2010, 09:48   #7
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I've got my AIS antenna mounted on the top spreader and it seems to work very well. No doubt the proximity to the mast and shrouds has some effect on the antenna pattern, but I don't think it's too significant.

On other boats I've seen GPS and satphone antennas mounted on the spreaders.
Do you have a photo of your installation, by chance? How did you mount it, exactly?
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Old 02-05-2010, 15:35   #8
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Looking for any pictures of spreader mounted antennas

I too am looking to install an (AIS transponder) antenna on the spreader. Any good installs to share? I am thinking upside down from the upper spreaders. Probably a shakespeare 5396.

Fair winds,

Matt
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Old 02-05-2010, 20:05   #9
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OK. Why upside down?

(Why is it me that always ends up asking these questions?)
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Old 02-05-2010, 20:24   #10
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No problem with upside down - RF pattern wise it is the same as upright. I have my #2 VHF antenna mounted upside down under the radar platform. Works just fine - except - the antenna is one of those with a replaceable whip and with vibration the whip keeps falling out. One time the whole guts inside the little base fell out. Other than that consideration - no problem with upside down.
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Old 03-05-2010, 07:39   #11
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FSMike, Upsidedown is for two reasons. First so that if the halyard wraps around the antenna it will fall away easily. Second, since the shrouds slant sharply inwards above the top spreaders but go virtually straight down vertically below there.

Osirissail,
No problems except the whip falls out and the guts fall out. heheh. I wondered about the water intrusion into the body. I'm still interested though. How'd you mount it to the radar mount? Any pictures?
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Old 03-05-2010, 08:54   #12
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The antenna has a right angle bracket supplied with it so I simply mounted the bracket on the side panel of the radar platform support. The supplied bracket has a long enough "leg" that it could be bent again for attaching to a horizontal part of the radar mount. Or you could make a new bracket or an extension for the supplied bracket. Not difficult.
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