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Author Topic: Boat Mobile- Antenna Suggestions  (Read 2858 times)
K3AN
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Posts: 787




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« on: April 27, 2006, 02:31:12 PM »

I live in a community on the shores of a large lake in western South Carolina. I am planning to operate HF from our pontoon boat. I'm thinking of adapting a 3/8-24 mirror mount, installing it at the top of one of the metal canopy supports. I will use a short run of braid and a large alligator clip to make a "ground" connection to the canopy frame. I'm planning on getting 3 Hamstick-type antennas, for 40, 20 and 17.

Quick band changes are not a priority. Keeping cost relatively low is a priority since this is just for fun, to while away a lazy afternoon on the water. Most operation would be with the engine off, anchored in a shady cove or drifting with the breeze.

What do you all think? Alternative suggestions are welcome.

Bill,
K3AN

P.S. Don't put off retirement a day longer than you have to!
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KT4NR
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Posts: 571




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« Reply #1 on: April 27, 2006, 06:05:20 PM »

Check on Hi-Q antennas. The support group has some suggestions for Maritime mobile antennas and they are good antennas. They will be a bit pricier but with the salt water and limited mounting options it may be worth the investigation.

Dan S
KO1D
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N8EMR
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Posts: 248




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« Reply #2 on: April 27, 2006, 07:27:05 PM »

Why not get you a marine SSB antenna. That an an antenna tuner makes an all band HF radio.
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K0BG
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« Reply #3 on: April 28, 2006, 06:53:38 AM »

Ground plane is EVERYthing. In this case, since you're going to be using Hamsticks, it doesn't matter much about the ground plane as the losses are already high.

It doesn't make much difference whether we're talking about a boat, car, truck, or base vertical, the major losses you have to deal with in the ground plane loss. A lot of amateur feel, that because they are atop sea water that magically they have a ground plane. That's not so. Most non metallic boats have some form of keel plate to provide a half way decent path to the water, morre for lightening protection than anything else. If the boat doesn't have one, you can always add one, and there are tons of info on the net about doing just that.

The suggestion about the auto coupler is a good one too, as you typically don't have a lot of room to store antennas. A back stay, or tall pole works well, as long as the other end of the coupler is grounded as best it can be on a keel plate. While the railings will work to some extent, remember thay are the OTHER half of the antenna and will radiate!

Alan, KØBG
www.k0bg.com
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K3AN
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« Reply #4 on: April 28, 2006, 09:25:43 AM »

I guess my original post wasn't clear on a couple of points. I'm on a fresh water lake, near the mountains in western South Carolina, not on salt water. The boat is a pontoon boat, with two 24 foot long polished aluminum pontoons partially submerged in the water. It's not a fiberglass hull.

The pontoon boat has a fixed metal canopy over the aft half of the boat. It's about 8 feet by 10 feet. The canopy is held up by metal supports, and the bottom of the supports are attached to the metal railing that surrounds the deck. This should be as good a ground plane as an average car, and better than a fiberglass RV body.

I know hamstick-type antennas are lossy, especially at 40M and below. What's a reasonably-priced alternative?
Again, quick band changes are not a necessity.
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K0BG
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« Reply #5 on: April 28, 2006, 04:39:34 PM »

Bill, the pontoons are perhaps a moderate ground plane. However, mounting the antenna atop a frame, whether or not it is physically attached to the pontoons, just raises the antenna higher above what little ground plane it woul have otherwise.

This is the same as mounting you base vertical on top of a 5 foot mast, and the radials are at the bottom of the mast. Quite obviously, this is not ideal.

Alan, KØBG
www.k0bg.com
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K3AN
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« Reply #6 on: April 28, 2006, 08:10:28 PM »

Installing the antenna so that its base is close to one of the pontoons is an option. However, I think it would be analogous to installing an HF antenna to the bumper of a car (old days, when cars had chrome bumpers!) vs. installing it on the roof or rear deck. Everything I remember reading said get the antenna up high. The boat's metal canopy is certainly larger than the roof of any car, van or SUV.

I'll probably end up trying different mounting locations. It's always fun to experiment.

So, which antenna?
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N1QKH
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« Reply #7 on: April 29, 2006, 06:02:47 AM »

I would go with the 17 and 20m hamsticks. The price is right and they easy to tune up. They are not all that efficient but, you can move up to something more elaborate if you "get into it", later on. The 40m hamstick will be more trouble to get working. An antenna analyzer would be a help in trying out different locations. You can be sure that a bad location for a hamstick will be a worse location for a screwdriver or bugcatcher because of the higher Q.

I don't get a warm fuzzy feeling about the copper braid  and alligator clip for a ground. Copper strap is better as long as it does not have to flex (wider is better). Clean bright metal connections with penetrox compound and bolts/screws are the way to go. If the alligator clip lets go in the middle of a QSO, your finals are toast.

73

Don N1QKH
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VA7CPC
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Posts: 2831




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« Reply #8 on: April 29, 2006, 05:50:16 PM »

I hate to disagree with K0BG, but here goes . . .

A Hamstick, or loaded mobile whip, mounted in the middle of your metal top, may see a reasonable ground plane on 20m. If the top is well-connected to the pontoons, that would be even better.

That's the simplest, cheapest arrangement. No need for fancy tuners if you're lucky.

Try it first.
 
If it doesn't work, my next suggestion would be a Hamstick dipole, elevated well above the metal top on a pole.  Or a "Dudleypole" vertical, using a 20' crappie pole, with a counterpoise trailing in the water.

The single Hamstick _uses_ the top, and the dipole and Dudleypole would work better if it weren't there.

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KC2MMI
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« Reply #9 on: April 30, 2006, 12:53:54 PM »

Bill, if you want a little casual fun during retirement...pick up a mylar balloon, a spool of 28g magnet wire, and a helium tank from a party store, Costco, or a local gas supplier.

You CAN actually send up a long wire via the balloon, over a lake that should be no problem, real cheap & simple to boot. There are also some folks on the web having fun with kite antennas, and balloon-kite hybrids.

Why limit yourself to mobile sticks when you literally can raise a real long-wire dirt cheap?
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