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Marine Antenna - shorted or non shorted

Old 03-01-2015, 01:59 PM
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Default Marine Antenna - shorted or non shorted

I guess it depends on the radio, but what is best for off shore use. Best set up and recommendations for matched radio /antenna
Old 03-01-2015, 02:19 PM
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Ground plane or no ground plane, is that what you are asking?

The outside braid will always be connected "shorted" in continuity to be radio chassis and the mount if it is metal.

I believe most production antennas are designed to be used without a ground plane as they were intended for a fiberglass boat.
Old 03-01-2015, 03:29 PM
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Sill confused 3db vs 6db 1/4 wave 1/2 wave 3ft vs 8 ft . metal vs fiberglass ?? many variables. Can someone explain best scenario for boat (fiberglass) ..Thanks appreciate the feedback.
Old 03-01-2015, 05:10 PM
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The 3 db and 6 db are the gain of the antenna with the 6 db having twice the gain of the 3 db one. 9 db is 4 times the 3 db gain. The gain is usually related to the size of the antenna. Most of the boat antennas are a fiberglass rod or tube with a wire running up the middle. Some of the shorter ones are a metal whip.

This is a website for Shakespeare Marine FAQ.

http://shakespeare-marine.com/node/238
Old 03-02-2015, 03:40 AM
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The 6db is what most powerboat antennas are.

The 3db is recommended for sailboat masts. While the 6db is stronger, it is a narrower beam that is sent out from the antenna, but it would have trouble transmitting to/from vessels close by as the signal would essentially go over the tops of power boats near by. Where as the 3db is a broader signal that allow you to "hit" these antennas lower and closer to you.

Where the overall effective distance of VHF antenna's is mostly effected by height, the fact the sailboat antenna is on the top of their mast, minimizes any distance "lost" by the 3db signal.
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Last edited by Recovery Room; 03-02-2015 at 06:45 AM.
Old 03-02-2015, 03:13 PM
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Regardless of antenna chosen, boat-to-boat will always be limited in range due to antennas at both ends being barely above the water, compared to boat-to-USCG, for example, who use tall towers or natural features to gain antenna height.

"My" USCG antenna, for example, is mountaintop, about 5,000 feet above water level...huge difference in range. This doesn't happen in flat Florida, but is common in New England and upstate NY, where tall mountains are close to the water. But, even a dinky 600' USCG tower in Florida is a definite benefit.

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