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Old 11-25-2020, 01:31 AM   #1
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Mapping antenna to radios

I've got four radios and four antenna on my boat, three are VHF and one is a CB.
I'd like to map which one goes to what radio but I can't think of a good way to do this. There must be some sort of trick to this and thought the TF trust might know. Was thinking that I could use a hand held VHF, perhaps with a disconnected antenna to map them but don't know if that will work. The reason for doing this is I would like to add splitter to one which is the highest on the stack for a new Vesper AIS transceiver.

Also, I suspect I may have some crosstalk due to how close some of the antenna are to one another.


Any suggestions?
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Old 11-25-2020, 01:48 AM   #2
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Coil wrap a wire around the antennas ( one at a time ) with a low power light bulb at the end. \key the mikes and see which one lights the bulb.

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Old 11-25-2020, 01:56 AM   #3
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Maybe an EMF app for your phone. Have someone transmit, click a mike while you move phone near each antenna.
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Old 11-25-2020, 07:57 AM   #4
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Disconnect the antenna at one radio, then see which one doesn't receive a test call. It would require a handheld, or use of one of the other radios as a transmitter. Should be pretty quick and easy.


Another way would be with an SWR meter, which on some radios is built into the radio itself.
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Old 11-25-2020, 08:01 AM   #5
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If tracing the coax is out of the question, this may work.
Compare the coax for differences. You may be able to match one or two.

You can tune all radios to a weak weather station then lay down one antenna. The reception of that one should drop off.

If that don't work then slide a full length of 1 inch EMT (metal) electrical conduit over a lowered antenna. The signal will go away on the covered antenna. Once you ID all of the radio/antenna pairs then return the "unused" conduit.
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Old 11-25-2020, 02:21 PM   #6
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Some good ideas here. First the CB antenna should be straightforward to identify because it will be a different length than the VHF Marine antennas.

I assume there isn't a connection at or near the base of the antennas.

I like High Wire's suggestions.

Another method would be to get a small neon indicator light with a non-metallic housing, tape or ty-wrap it to the end of a wood pole, and then place it near each antenna while someone keys the transmitter of each radio with the transmit power set to High. You may need to move the light along the length of the antenna and conduct the test at night. The light should illuminate near the active antenna. Note that physical or electrical contact with the antenna is not required - just close proximity.



Good luck!



Example neon indicator: https://www.amazon.com/Indicator-Rep...6331831&sr=8-3
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Old 11-25-2020, 08:39 PM   #7
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I knew you guys would have some good ideas. I like the idea of setting each radio for a weak weather station and dropping the antenna vertical or covering it, would probably use aluminum foil. Hopefully I can ID a couple of them with the coax, but it may be tricky at the antenna end to decipher. A couple of the antenna are the same model so for sure I will need do do some trick to find it. I'll let you know how it goes.

Thanks.
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Old 11-26-2020, 01:46 PM   #8
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Quote:
Originally Posted by High Wire View Post
If tracing the coax is out of the question, this may work.
Compare the coax for differences. You may be able to match one or two.

You can tune all radios to a weak weather station then lay down one antenna. The reception of that one should drop off.

If that don't work then slide a full length of 1 inch EMT (metal) electrical conduit over a lowered antenna. The signal will go away on the covered antenna. Once you ID all of the radio/antenna pairs then return the "unused" conduit.

Great idea! And if you ground the conduit, you create a Farraday Cage that will block even strong signals.
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Old 11-26-2020, 04:34 PM   #9
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What about sending a tone. https://www.amazon.com/Extech-40180-.../dp/B00023RVNO

I never tried it with coax, but it works great with normal wiring!
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