Posts: 2754
Location: Mauston, Wisconsin | Listen to misterperch. Otherwise, take the boat to a shop that specializes in two way radio communications. Ask around, these same folks usually take care of police, ambulance, taxi, and business FM communications radios.
Tell them you want them to check the VSWR of the system. Be sure that you have them check the primary frequency's you are likely to be using, i.e., emergency marine channel & talking to buddie's channels. The closer the channels are to together with each other for frequency the better.
http://www.google.com/webhp?source=search_app#hl=en&sugexp=les%3Bcp...
Most off the shelf radio systems -> radio, coax, and antenna are not optimized for specific frequencies. Ask them to tune the transmitter output for lowest VSWR at the mid-point between the frequencies you are using. If the radio in question has a final output amplifier that can be tuned, they can also lock it in for maximum line-of-sight transmission- lowest VSWR at your primary frequency. They have to do it as a system = radio->coax-> antenna.
http://www.navcen.uscg.gov/?pageName=mtvhf
Don't forget the curvature of the earth, if you can't see it , you usually can't talk to it unless you have a brute horsepower FM transmitter or its very close by.. behind an island, etc. Then there's also "skip" but that something that is totally atmospheric controlled. I have talked between Ft. Bliss, Texas (Dona Anna Range Control) and Ft. McCoy, WI on a 75W radio FM radio that I tweaked for our our firing range and air traffic control operational frequency. I was surprised when McCoy Tower came back on the radio check call. But, I would never bet on skip.
It's already been said, if you can hear them and they can't hear you or the reverse, its a waste of time. Their VSWR may be bad, as has been stated previously the length of the coax and how its installed are a major factor. If the VSWR is low on your radio the majority of the power output is leaving the antenna. Beyond that, what you hear is driven by receiver sensitivity and where you have set the squelch. If its an emergency situation - turn off the squelch, that will allow you to hear the weaker signals. Longer antennas are better, but also a major pain on a boat. If you're only trolling no problem, put it on a mast. Casting W/multiple people, etc. no fun if you're the guy who keeps wacking the antenna with his rod...... Commercial fisherman and charter captains understand the on the water value of a good radio. Maybe one area where cheap is not the way to go......
Good luck,
Al
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