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Old 05-05-2015, 16:13   #1
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VHF Transmission Problem

My icom VHF receives message input clearly. Voice messages come through just fine. However, based on several test transmissions, it does not transmit my voice output well at all. My voice output is extremely scratchy and almost unintelligible. It's an old unit, and I'm willing to replace it if necessary, but I don't want to waste money if a new unit won't fix this problem. Could the antenna have anything to do with this?

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Old 05-05-2015, 17:14   #2
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Re: VHF Transmission Problem

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Originally Posted by BozSail View Post
My icom VHF receives message input clearly. Voice messages come through just fine. However, based on several test transmissions, it does not transmit my voice output well at all. My voice output is extremely scratchy and almost unintelligible. It's an old unit, and I'm willing to replace it if necessary, but I don't want to waste money if a new unit won't fix this problem. Could the antenna have anything to do with this?

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The antenna has nothing to do with the audio. You could have a damaged microphone or a problem with the radio itself.

The only way to tell for sure if your problem is the antenna or the radio without test equipment is by substitution with known good parts. One other possibility is a power problem where corroded or loose power connections aren't delivering full battery power to the radio. Check the voltage between the positive and negative leads where the radio connects while transmitting and see if there;s a voltage drop. If there is, correct it and try again.
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Old 05-05-2015, 17:53   #3
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Re: VHF Transmission Problem

I have the same problem with my new AIS. I can see targets for >20 miles, but people can only see me for < 1 mile.
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Old 05-05-2015, 17:57   #4
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Re: VHF Transmission Problem

Don't transmit without an antennae hooked up. I'd say it's corroded or broken wires in insulation somewhere in the installation.
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Old 05-05-2015, 17:58   #5
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Re: VHF Transmission Problem

Yes, the antenna can have something to do with this. If the VSWR is very high (say more than 5:1) the transmitter portion of the radio can have distortion, dropouts or low output power. But the coax is a more common source of problems. If the outer conductor of the coax has a bad connection either at the antenna or at the radio this kind of behavior can result. The receive part works fine but the transmit doesn't work well. The outer connection can be damaged by corrosion because it wasn't sealed well enough against water.
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Old 05-05-2015, 19:08   #6
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Re: VHF Transmission Problem

I have a Solar controller that messes up my VHF in and more so out. If trying to talk to or hear a station more than a few miles away I must turn off the controller. Have you installed one recently?
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Old 05-05-2015, 19:12   #7
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Re: VHF Transmission Problem

I have installed a solar controller recently. Problem: I don't want to turn it off to operate the vhf. Are you sure the solar controller is my problem?

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Old 05-05-2015, 19:46   #8
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Re: VHF Transmission Problem

Turn solar system off and check if the problem goes away or not. If the solar is the problem there are things you can do about it.
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Old 05-05-2015, 19:47   #9
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Re: VHF Transmission Problem

Just turn it off and test the radio. If its better its part of a problem if not it isn't. At least you can narrow it down.

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Old 05-05-2015, 20:16   #10
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Re: VHF Transmission Problem

My controller (MPPT) searches and puts out serious RF noise. It is obvious . Even boats next to me are affected. I will be changing it out soon. You can hear it clicking and static . Just turn it off and eliminate this issue or recognize it. It only takes a moment.

You can also do a quick check with a multi meter. Just disconnect the antenna wire from the radio and use the continuity check between the center and the ground on the antenna wire . It will show open if OK.
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Old 05-05-2015, 21:28   #11
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Re: VHF Transmission Problem

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........
You can also do a quick check with a multi meter. Just disconnect the antenna wire from the radio and use the continuity check between the center and the ground on the antenna wire . It will show open if OK.
Not necessarily. Many/most marine VHF antennas will show a DC short between the center conductor and braid. They're designed that way.

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Old 05-05-2015, 22:04   #12
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Re: VHF Transmission Problem

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Originally Posted by BozSail View Post
My voice output is extremely scratchy and almost unintelligible.
Quote:
Originally Posted by rwidman View Post
The antenna has nothing to do with the audio. You could have a damaged microphone or a problem with the radio itself.
i agree with rwidman here ... might just be a damaged mic ...

btw, did you check the swr?
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Old 05-05-2015, 22:24   #13
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Re: VHF Transmission Problem

Not an expert by an shot, but I had a similar problem last year. I was able to hear the harbor I was heading into, but they were not able to understand
/ hear me. I was about 1 mile out. There was another boat about half way between me and the harbor. They were able to hear me and forward my intentions to the harbor. Once I returned and looked into the issue, it turned out that while the contractor was installing a new mast light, he had damaged the connector to the VHF antenna. Once he fixed the connector, all was good again.
I also then went out and bought a handheld unit.
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Old 06-05-2015, 11:21   #14
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Re: VHF Transmission Problem

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I have the same problem with my new AIS. I can see targets for >20 miles, but people can only see me for < 1 mile.
I'm such a dinosaur I don't even know how they work. Sorry I can't help.
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Old 06-05-2015, 12:36   #15
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Re: VHF Transmission Problem

If it is an Icom M504 there are known problems of this type. Last year I had a similar problem with my Icom M504 which I purchased in 2009. I sent it back to them and they promptly made the repair without charge even though the warranty period had expired. I read they had a bad batch of RF Filters. All I paid was one way shipping. Great customer service!
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