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VHF antenna horizontal mount??

Old 05-22-2008, 12:03 PM
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Default VHF antenna horizontal mount??

I am curious to know that if i mount my antenna under the gunnel, horizontally rather than verticly if it will work and if so will i lose any reception and distance?? thanks
Old 05-22-2008, 12:12 PM
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Default Re: VHF antenna horizontal mount??

It will work very poorly. VHF is line of sight - height is everything. In addition, the antenna radiating pattern would not work well at all in that plane so you would have extremely spotty transmission reception to other boats.

Ken
Old 05-22-2008, 12:44 PM
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Default Re: VHF antenna horizontal mount??

Vertical antennas have to be VERTICAL.

If you mount them on their side, you have a DIPOLE antenna. Not a vertical. It will have horizontal polarization and suffer an automatic 20 db loss (more or less, NEVER take a db figure as an exact number).

By the way, all you people who leave your vertical antenna raked back 45 degrees - whats up with that? If the antenna is not vertical it is not working as well as it could.

Ever see a radio geek car with antennas raked back? Nope. Ever wonder why?
Old 05-22-2008, 02:49 PM
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Default Re: VHF antenna horizontal mount??

One good thing about putting the VHF antenna under the gunnel is you can *always* see the guy you're talking to. You could probably hand him a sandwich too.
Old 05-23-2008, 07:45 AM
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Default RE: VHF antenna horizontal mount??

ChipSmith - 5/22/2008 3:03 PM

I am curious to know that if i mount my antenna under the gunnel, horizontally rather than verticly if it will work and if so will i lose any reception and distance?? thanks
Seriously, no, it will not work very well at all. I'm assuming the installation instructions that came with it mentioned mounting it vertically.
Old 06-16-2011, 08:11 AM
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Mounted horizontally, your radiation pattern would be (roughly) a semicircle out to both sides and straight up, right? So, if you were beam-to another boat, you might get some distance.... but little fore and aft.

Piling on: No. You need to mount it vertically if you want it to work properly.
Old 06-16-2011, 08:45 AM
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Originally Posted by Lazy_Iguana View Post
Vertical antennas have to be VERTICAL.

If you mount them on their side, you have a DIPOLE antenna. Not a vertical. It will have horizontal polarization and suffer an automatic 20 db loss (more or less, NEVER take a db figure as an exact number).

By the way, all you people who leave your vertical antenna raked back 45 degrees - whats up with that? If the antenna is not vertical it is not working as well as it could.

Ever see a radio geek car with antennas raked back? Nope. Ever wonder why?
Vertical to vertical or Horizonal to horizonal will work, but Vertical to horizonal will give you the typical 20db signal loss. Off topic, I prefer horizonal polorization better. Has less noise due to most noise being vertical polorized. Also some suggest a horizonal polorized signal will follow the earths curvature further than a vertical polorized signal. Not to many boats fully horizonal polorized, but 1/2 way there. Great topic.

Charlie
Old 06-16-2011, 10:55 AM
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The gain pattern of a whip antenna looks like a Figure 8 on its side when the dipole is vertical....thus you get gain toward the shore (or oout toward other boats). Horizontally, half your pattern is underwater and the other half is pointed into outerspace. The pattern that is aimed at the Coast Guard is way down (the 20 dB mentioned earlier). You'd be better with no antenna other than an omni.
Old 06-16-2011, 11:04 AM
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Originally Posted by Lazy_Iguana View Post
Vertical antennas have to be VERTICAL.

If you mount them on their side, you have a DIPOLE antenna. Not a vertical. It will have horizontal polarization and suffer an automatic 20 db loss (more or less, NEVER take a db figure as an exact number).

By the way, all you people who leave your vertical antenna raked back 45 degrees - whats up with that? If the antenna is not vertical it is not working as well as it could.

Ever see a radio geek car with antennas raked back? Nope. Ever wonder why?
Why does it become a dipole when the orientation changes from vertical to horizontal?
Old 06-16-2011, 12:16 PM
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Originally Posted by Team Ruby View Post
Why does it become a dipole when the orientation changes from vertical to horizontal?
Mixed metaphor, I guess. A vertical VHF-FM whip antenna happens to be a dipole antenna. If you take the dipole and turn it sideways, its pattern is a miserable fit for a marine application.

You can have a horizontal dipole antenna that would make sense for a different application.
Old 06-16-2011, 03:28 PM
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In the computer world we used to say that a picture is worth a kiloword. Here is a picture depicting the signal transmitted from a marine VHF antenna:



The red lines represent the signal from a typical 8' vertical antenna.

Now imagine reorienting that same antenna 90 degrees to a horizontal position. The signal is directed into the water and directly (straight up) to the sky (sun, moon, stars, etc.) You will have very little signal in the horizontal plane where other boats and shore stations are.

Imagine it raked back at a stylish 45 degrees as Lazy_Iguana mentioned. Much of the signal is radiated into the water and to the sky.

If you expect your VHF to work as designed, the antenna must be mounted vertically.

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