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Old 07-19-2016, 04:46 PM   #1
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Feedback issue with VHF's

I was out on the skiff the other day and my wife contacted me on "9" when the other radio was switched to "16" and she got a very strong feedback squeal from the radio on "16". Is this an antenna interference issue or something else?


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Old 07-19-2016, 04:49 PM   #2
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Antennas close? ........ or was one on scan or dual watch?
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Old 07-19-2016, 05:13 PM   #3
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Antennas close? ........ or was one on scan or dual watch?
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Old 07-19-2016, 05:47 PM   #4
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Feedback issue with VHF's

Yes, unfortunately the antennae are closer than I'd like. It doesn't occur on all channels, just with 9 and 10, which affect 16. If it is an antennae issue, it will be hard to resolve. So why isn't this an issue with fishing boats with a raft of antennae up on a mast? The radios were not on dual watch or scan.

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Old 07-19-2016, 06:08 PM   #5
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It can also be a problem with the antennas appropriately spaced apart but the leads run through a common chase. Quality cable and shielding can help.
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Old 07-19-2016, 06:31 PM   #6
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Were you transmitting on high power or 1 watt ?
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Old 07-19-2016, 06:48 PM   #7
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Feedback issue with VHF's

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Were you transmitting on high power or 1 watt ?
Probably high power. That's the default.

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It can also be a problem with the antennas appropriately spaced apart but the leads run through a common chase. Quality cable and shielding can help.

Yes it's a common chase. Hmmm. I'll have to dig a little deeper. One of the antenna is 8' and the other is 24. I was hoping the transmission "doughnuts" would have verticals separation. I guess perhaps not.

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Old 07-19-2016, 08:11 PM   #8
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See if the problem goes away on low power.
Boat high - skiff high
Boat high - skiff low
Boat low - skiff high
Boat low - skiff low
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Old 07-19-2016, 10:53 PM   #9
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Also, if you have enough antenna lead, swap leads to the radios and see if the problem persists. You never know...
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Old 07-20-2016, 02:13 AM   #10
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A simple fix would be to use another working channel other than 9 or 10 or simply turn off the radio not being used when communications with your skiff is taking place. I would try it on low power first though. If you are within a few miles of each other low power should be ample.
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Old 07-20-2016, 10:22 AM   #11
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Operating multiple radios in close proximity to each other can be problematic, even though they're utilizing different radio frequencies and different bands of the frequency spectrom. Some radios have better filtering than others and a poor or broken antennae setup can also cause problems.

Even high end commercial radios operating in proximity to each other are susceptible to harmonic and RF interference. Our mountaintop sites were often nightmares with 8 - 10 companies operating multiple radios on many different frequencies. Our systems utilized filters and tuned cavities to eliminate these problem. Even so, some radios and frequencies were incompatible and could not be operated from the same site.

If this continues to be a problem for you, call in an electronics tech to trouble shoot your setup. Could be the radio or as simple as a bad coaxial cable, connector or switch.
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