" JimH" jimh_osudad@yahooDOT comREMOVETHIS wrote in message
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"NOYB" wrote in message
ink.net...

"Shortwave Sportfishing" wrote in message
...
On Fri, 13 Jan 2006 23:35:25 GMT, "NOYB" wrote:


"Wayne.B" wrote in message
...
On 13 Jan 2006 09:56:30 -0800, "
wrote:

According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't have
it. My boat is a fiberglass boat. What's the alternative? Does
this
mean that I cannot use 3dB antenna?

There is no need for a ground with a VHF antenna.

Either the 3 db or 6 db antenna will be adequate for near shore
coastal operation.


I'm with Wayne on this one.

The dB rating plays a relatively minor role in the distance the signal
travels. The height of the transmitting antenna plays a larger role.
But
the height of the receiving antenna is the most important element.

Example:
A 3' antenna mounted on the top of the gunwale of a small boat might be
5'
above the water line. It can travel only 5 miles to another antenna
that
is only 5' off the water...but can travel 15 miles to an antenna that
is
100' high (like at a Coast Guard station).

An 8' antenna mounted on the same gunnel can travel 9 miles to another
antenna that is only 5' off the water (big difference!), but only
travels
18
miles to that 100' antenna (a not so big difference from the 3'
antenna).

If the CG antenna is 250' above sea level (mounted on a tower on a
mountain
for example), the 3' antenna can travel 23 miles...and the 8' travels
25
miles.

So the question is...
Who do you want to call with that radio?

Another boat within 5 miles? Then either antenna is fine.

The Coast Guard when you're 10-15 miles from shore? Then either
antenna
is
fine once again.

Here's a good link to explain this further:
http://www.yachtworks.net/Store/antennas.htm

finally - a civilian who gets it.

That's the engineer in me. I like to read how things work before making
my purchases.




Looking at specs is fine. But what happens when the boat, intended for
only
near shore use, loses power when at the fringe range of the 3 foot antenna
and there are no boaters anywhere close?

I see no downside with going with the 8 foot antenna.



The downside of the higher gain antenna, is that when the the seas are
rolling the energy radiated from the antenna on a small boat will be
directed toward the water or toward the sky. Why not mount the 3 dB antenna
high, or use an extension?