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Antenna height

Old 04-23-2008, 01:36 PM
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Default Antenna height

Will be adding a VHF to my river boat as soon as I get it back from being rigged with the motor.
I remember reading awhile back that VHF antenna's will reach as far as line of sight. Seeing I am an electrical dummy what brand and height antenna would you recommend and why?
It will be rail mounted on an alunimum boat.
Old 04-23-2008, 01:45 PM
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Default Re: Antenna height

Well, your typical boat use for a 20' and smaller would be either a 3-4' metal whip or 8' shakespeare. I've used both on my runabouts and currently have a 3' metal whip antennae from the ttop on my center console.
If you trailer, make sure you have a good place to strap the top half down for traveling.
Old 04-23-2008, 03:47 PM
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Default Re: Antenna height

I have space to use a 8 foot glass modeland can fold it over and secure it to the rails when I am trailering. But would an 8 footer offer me any advantages over a 3-4 foot whip?
Old 04-23-2008, 04:36 PM
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Default Re: Antenna height

A 6db 8' antenna will give you considerable range over a 3' 3db antenna. That is if you can use the range as if your rocking and rolling in a 17' skiff the 6db antenna may not help much. Personally I would go with a securely mounted 8'.
Old 04-24-2008, 04:32 PM
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Default Re: Antenna height

Height is everything. A cheap glass 8' antenna will 'see' several miles further than a 3' antenna mounted in the same place. A cheap antenna will have a fatter donut of reception than a more expensive antenna, meaning it will be less affected by a small boat's rocking and rolling. On a river, a couple feet of height will reduce the shadow effect of low terrain around the bends.
Old 04-24-2008, 06:36 PM
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Default Re: Antenna height

What about a 3' whip mounted on a 4' extension?
Old 04-24-2008, 07:52 PM
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Default Re: Antenna height

Snowwolfe - 4/23/2008 6:47 PM

I have space to use a 8 foot glass modeland can fold it over and secure it to the rails when I am trailering. But would an 8 footer offer me any advantages over a 3-4 foot whip?
Yes. That's a better choice as it focuses the energy in a horizontal plane.
Old 04-25-2008, 06:14 PM
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Default RE: Antenna height

Assuming VHF radio, you're right that it is all about line-of-sight. If your antenna top is 7 feet off the water, the horizon (according to Chapman's) is 3.55 miles away. So your range to a similarly equipped boat is roughly twice that, or 7 miles.

If your antenna is 4 feet higher (11 feet), the range from its top to the horizon is 4.46 miles, or roughly 9 miles to a similarly equipped boat. So four feet higher gains you only 2 miles or so reach over the horizon.

The horizon is like a low mountain out there that quickly blocks line-of-sight transmissions. If you are in hilly land instead of at sea, it's just worse.
Old 04-25-2008, 08:05 PM
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Default Re: Antenna height

As you are in rivers, you are lower than anything else around, especially the river banks may block your signal.

I would not hesitate mounting the antenna on a pole to get it higher. After that, the antenna type is IMO secondary.

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