In article . net,
"Ted" wrote:
wrote in message
oups.com...
I have a small sail boat (26') used for coastal cruising. It
would probably never be beyond 25 miles from the shore
line (maximum) and normally no more than 1 to 3 miles.
At present... it has a 1/2 wave Shakespeare mounted about
5 feet above the water line on a stern rail.
My question is...
Would I be *much* better off... moving the antenna to the top
of the mast...
No.
There would be a small improvement but I don't think you would even notice.
I recommend you leave the antenna where it is and if you ever have an
emergency be sure to point your sailboat (if you can) so that the boat is
not between the antenna and the shore. If you are disabled and adrift off
shore then occasionally your boat will not be between your antenna and
shore. These are the best times to call for help but by all means, call for
help constantly until someone hears you. If you are out of sight from shore
then I recommend you get an epirb.
http://www.sarsat.noaa.gov/emerbcns.html
I also recommend you keep a cell phone aboard. I have found it to be much
more handy than marine vhf radios.
With both Marine VHF and Cellular Service, you are looking at the maximum
range of transmission being determined by LOS (line of sight) plus a
extending factor of signal bending, which is Frequency dependant, and
which is maybe 5 to 10% more, which makes up the Radio Horizon. USCG
Remote Radio Sites are typically located at high elevation points along
the coastline, so as to maximize their coverage out to sea, where
Cellular coverage is specifically designed to minimize adjacent Cell
overlap but give continious coverage along the coastline. These are
two, basically, Mutually Exclusive determinations.
Moving the Marine VHF Antenna to the top of the mast, WILL certainly
extend the VHF Range for the vessel over an antenna that is 5 ft
above the water. Remember it is just not the distance offshore that one
needs to consider, it is also how far the USCG Site is up or down the
coast from your position as well. Another thing to consider is the
Antenna Gain Specs of the Marine VHF Antenna, which will determine the
3db Vertical Antenna Beamwidth, which intern will affect the ability of
the antenna to communicate to shore stations when the vessel is healed
over while navigating crosswind.
For sail powered vessels, it has always been prudent to have the VHF
Antenna, as high as possible, with no more than 4.5 db of gain in
the antenna, so as to minimize the healing degradation of maximum
effective range. Cellular should NEVER be considered a substitute
for Marine VHF communications, but it can be helpfull as a backup
system.
Also remeber that Marine VHF will allow communications with other
vessels in your area, as well USCG Remote Radio Sites, where Cellular
MUST be able to communicate with the Shorebased Cellsite in order to be
of use in communications. There is no vessel to vessel communications
with cellular, if you are not within cellular coverage.
Bruce in alaska
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