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Old 05-20-2014, 12:31 PM
redfish727 redfish727 is offline
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Join Date: May 2014
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Default Marine Transmission Question

I'm trying to gain a better understanding as an in-shore fisherman of how VHF marine radios work and would appreciate if someone could answer this question.

Scenario: I transmit a radio check or distress message on Channel 16 to the Coast Guard over my handheld 5W Cobra VHF Marine Radio 1/4mi from shore, the coast guard can hear me and responds.

Question: Is my low-power message automatically relayed by the Coast Guard station over 25W or higher signal so that a boater 20 miles from shore could hear my message? Or, is it more likely that the Coast Guard heard my message because I'm close enough to shore, but my 5W transmission was too weak to be picked up by that boater 20 miles offshore (let's say he has a fixed-mount 25W radio)?

I'm not looking for "why would you do this" responses, I'm looking to better understand how tx/rx works and more specifically how far a 5W radio transmitting over CH16 near shore will realistically be heard by other boaters.

Thanks so much.
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Old 12-31-2014, 03:24 PM
K6CPO K6CPO is offline
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Join Date: Dec 2014
Posts: 96
Default Re: Marine Transmission Question

I'm going to answer this even though it's an old post. The information might be useful to someone else.

Based on my monitoring of Channel 16 in San Diego, CA, here's how the Coast Guard here handles distress calls. If a boater making a call on CH. 16 is not in "immediate danger" the CG will ask them to come up on a different channel, usually 22A (Coast Guard working channel.) They will then ascertain if the boater is a member of one of the commercial tow services. If the boater is a member, then the CG will contact the service, who will handle the assistance from there. If the boater is not a member of a service and is unwilling to pay the cost of the service, then the CG will ask if the boater wants a general assistance broadcast made on their behalf. If the boater says yes, then the Coast Guard will make the broadcast.

If the boater is in immediate danger of sinking, on fire or going up on rocks, the Coast Guard will dispatch an asset to assist the boater.
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