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ContinuousWave: Small Boat Electrical
Two Radios Aboard
|Author||Topic: Two Radios Aboard|
posted 02-22-2006 04:51 PM ET (US)
I'm am curious why some people have more than one VHF installed and what the implications are. Some questions:
What are the advantages over having a handheld as a backup?
I imagine you would only have one on at a time, otherwise do you get feedback when hailing 16 on one?
Is this more of a "Heck, I have this new radio but the old one works fine so why not use it as a backup" kind of thing?
Should this be a separate thread? [YES, I have separated it--jimh.]
posted 02-22-2006 05:04 PM ET (US)
I always take my handheld VHF (submersible) just in case I find myself overboard. I also carry my handheld GPS. I consider both of them as important as my PFD.
posted 02-22-2006 05:08 PM ET (US)
I also have a handheld VHF and GPS on me and would never do it otherwise, but wonder about dual permanent VHF installations.
posted 02-22-2006 05:17 PM ET (US)
Can't say that I've ever seen them on boats but we had dual radios on the C-130 aircraft in the Coast Guard.
posted 02-22-2006 05:43 PM ET (US)
Several of the Monterey commercial dive boats have multiple
VHFs. One has one at the main helm and one at the flybridge.
The other (no flybridge) has two at the main helm. One is
permanently on 16, the other is on the working channel.
Hail the first radio, hang up the mike, yack on the second.
posted 02-23-2006 12:45 AM ET (US)
[This discussion was separated from the tail end of another regarding VHF Marine Radio communications and range.]
I believe it is fairly common for vessels to carry both a fixed installation VHF Marine Band radio and a hand held transceiver.
Two radios operated in close proximity can interfere with each other. There are two kinds of interference: RF overload and audio howl-around.
The presence of a very strong RF signal nearby, such as the output from one radio while transmitting, can desensitize the receiver in a nearby radio. In extreme cases, a radio could be permanently damaged by too much RF power too close to its receive antenna.
During transmit, if a nearby radio is receiving the transmission and reproducing it on a loudspeaker, there is the potential for audio howl-around if the microphone of the transmitter can pick up the loudspeaker.
posted 02-23-2006 07:45 AM ET (US)
I have 2 permanently VHF radios and a handheld that I carry in the ditch bag. Both fix moounted VHF's are connected to 2 seperate GPS units. I also carry a handheld GPS in the ditch bag. The ditch bag is stored right next to the life raft. I have redundancy for one reason safety. I fish 50 miles offshore in a 21' single engine Whaler and value my life and the others with me.
I also carry an emergency VHF antenna (small one with a suction cup for mounting purposed) just in case I lose both of my permanently mounted VHF antennas.
Better to be safe than sorry.
posted 02-23-2006 09:32 AM ET (US)
Do you know if handhelds are designed to deal with these phenomena? How close is close? I think many people commonly have their handheld on while also using their fixed mount radio. Are we damaging/shortening the life of our handhelds?
posted 02-23-2006 02:21 PM ET (US)
I've used a handheld for years right along side a hard mounted VHF with absolutely no problems. Everyone I fish with has 2 VHF and carry handhelds.
posted 02-23-2006 09:31 PM ET (US)
I don't know of any data regarding the maximum signal strength to which a VHF Marine Band radio can be exposed without damage. But I would not put my handheld right next to the antenna of a fixed radio and transmit at 25-watts.
The ability of a radio to tolerate strong signals without overload varies widely, and this is one of the more important qualities of a radio. Unfortunately, this type of information is not often available. The better radios tend to be more resistant to overload.
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