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post #1 of 11 Old 08-04-2010 Thread Starter
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VHF weak

Radio check - having trouble being heard on my 3 year old ICON VHF. A responder a few miles away said I sounded "very far away." I did the easy stuff; checked power and antenna connections both at the radio and up the mast. No help.

I put a volt meter on the radio which read 12.5 volts. When i transmitted at high power, voltage at the radio dropped to 11.4 volts. The battery is new. Seems like a big drop, but i have no perspective.

One other note: The CD player gets really hot when I play it, like the Cd is really hot when I eject it. both are hooked to the same ground buss.

Any ideas?
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post #2 of 11 Old 08-04-2010
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Did you check the VHF output using an SWR meter? If not, then you really need to do so. The SWR meter will tell you how much of a loss you're getting from the coax wiring and antenna. If the coax cable is damaged somewhere between the radio and the antenna, everything may look fine, but it will result in a weak broadcast.



I'd point out that if you do have a damaged coax cable, you could be frying your VHF radio every time you transmit, if enough of the power is being reflected back to the radio.

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post #3 of 11 Old 08-04-2010
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Ans SWR meter might be informative but keep in mind, as an example of how misleading it can be - if you terminated the coax into a light bulb, the SWR would be perfect but nobody would hear you.

You certainly have a significant voltage drop which can cause many radios to produce only a fraction of their rated output, often with distorted FM. I'd suggest you concentrate on that regardless of any other problem you may or may not have with the coax or antenna.
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post #4 of 11 Old 08-04-2010
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Try plugging another antenna into your radio (go to West, buy it, try it and then return it). If this doesn't fix the problem , increase the guage of the wiring between battery and radio and see if that helps.
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post #5 of 11 Old 08-04-2010
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You need a better report than "sounded very far away". Was your signal "in the noise" indicating a weak overall signal level or was your signal "full quieting" but still weak, indicating a transmit audio problem. Also, how far is "a few miles" and how high are your respective antenna's? Maybe you were just out of range. The typical voltage requirement for these radio's is 13.8 +/- 15% which means 11.73v is the lower limit. In general, you do not want your voltage at the radio to drop more than 3% of the battery voltage while still being at or above the lower limit of 11.73v. Yours was reading 11.4 which is low, but not so bad as to cause a major drop in power output. A drop of a few watts sounds like a lot, but is really insignificant. Your first prioity should be to fix the voltage drop problem. This could be due to a battery problem, inadequate wire size and/or loose/dirty connections. Corroded fuses/fuseholders are a prime suspect. Then you need to find someone to give you a better signal report and you need to make sure the other station should be within acceptable range for good communications. You can do this using one of a number of VHF line of sight calculators available on the internet.

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post #6 of 11 Old 08-04-2010 Thread Starter
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Thanks for the replies. I will be going out to the boat in a couple of days. I bought a new ground buss - one of the cable attachments (there are two) has a stripped stud down in the buss itself. I will fix that and see what happens. I have a sailboat with the antenna at the top of the mast. I usually don't get anyone to answer. I also bought a new antenna (on sale), but can still return it if the ground buss fixes the problem.
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post #7 of 11 Old 08-05-2010
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When using your radio, do you "close talk" your mic or hold it away from your mouth as do some?

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post #8 of 11 Old 08-09-2010 Thread Starter
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Replaced the Bus Bar. I really thought that was the problem . . . but no! Same low voltage. I have asked around but no one seems to have an SWR. West wants $199+ shipping & tax for the Shakespare. Seems pricey. Anyone got a different brand/source they like?
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post #9 of 11 Old 08-09-2010
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Buy a short, inexpensive coax cable. Be sure it is for VHF transceivers, not for cable TV. They are not the same. Since you bought an antenna, hook it up to the new feedline and unplug the existing antenna. Plug in the new one. Depending upon the antenna type, it may need to be mounted to work perfectly, but if there is a problem with the existing antenna or feedline then you should see a dramatic improvement even if the new antenna is just propped up in your cockpit. There will probably be no change in the voltage drop.

If there is no improvement, plug the original antenna feedline back in. Run some nice heavy 10 gauge cable directly from your battery to your VHF radio. Try again. Make sure the connections are tight at the battery end and the radio end. This time also check the voltage drop. If the problem goes away, then you have a electrical wiring problem. Start tracking it down. If you tell me the length of the wire run I can tell you the minimum wire gauge you should use.

The important part here is, change one thing at a time. otherwise, you won't know which change fixed the problem.

If none of this works, call Icom. You may have a bad final amp in the radio. A three year old radio should not be easily damaged by bad SWR, but even the best equipment can fail.

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post #10 of 11 Old 08-10-2010 Thread Starter
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Thanks JARCHER. Sounds like a plan . . . and I do need a plan. Hopefully I can get back out to the boat later in the week.
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