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Old 06-10-2015, 05:53   #1
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Defective VHF or Antenna?

Hello All,

I have a 10 year old ICOM 422, mounted inside the boat, that receives just fine and transmits just fine on low power. However, when transmitting on high power, only a continuous beep/squeal is actually output from the radio. (I use my handheld VHF to test.) There is plenty of power to the radio; the batteries are always topped off and the wiring is all well protected inside.

The other side of this coin is the 29 year old coil-base steel whip antenna mounted at the masthead. To the point, does anyone know if these symptoms are indicative of the coil in the antenna failing (less than $100 replacement) or the radio failing (several hundred dollar replacement).

TIA

Jim
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Old 06-10-2015, 06:09   #2
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Re: Defective VHF or Antenna?

Hi Jim, don't know if this helps, but at least on my boat, I cannot even get reception from the fixed VHF to the handheld unit, although the local coastal station 15nm away can be reached without problem. Just wondering if your problems may be related to too close proximity between the radios? Have you tried reaching some other station on high power?

Markus
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Old 06-10-2015, 17:38   #3
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Re: Defective VHF or Antenna?

Thanks for that, Sandbar. The antenna is about 40' away from the radio and I'm pretty sure I've successfully tested the radio this way in the past so I don't think too little distance is the problem. Also, I was attempting to contact another boat I know was in range and monitoring the channel and was unable to contact them. That's what got me wondering if there was a problem in the first place.

Thanks again.

Jim
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Old 06-10-2015, 18:30   #4
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Re: Defective VHF or Antenna?

Hi Jim.

I think Markus has a point, at least worth testing. The output of the fixed VHF on high power only 40' away could overload the front end of the receiver in the handheld causing the squeal. Worth taking the handheld a few hundred feet away and trying it again.
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Old 06-10-2015, 18:37   #5
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Re: Defective VHF or Antenna?

The best way to isolate is get your hands on a SWR/power meter and a dummy load. Put together as radio meter then dummy load. Check power and SWR. Now replace dummy load with antenna and see if results are similar. Note your power output into the dummy load should be about 20+ watts and SWR should be 1 probably slightly worse than that with antenna but not much. Note if it proves to be antenna before forking out the money for a new one take it down and try on a short cable. The problem could be the connectors or cable itself. These are usually more likely for the symptoms you are stating i.e. Works low power but not high. But the only way to check for sure is with the equipment. Scour the marina for an active ham he might have the equipment on board or at home. I carry them on board but won't be near Michigan for a few years yet.

PS make sure meter is ok for 156 Meg's some of the cheaper meters are for HF only and stop some where north of 30 Meg's.

Cheers

Mark
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Old 06-10-2015, 18:38   #6
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Re: Defective VHF or Antenna?

Whoops just noticed dropped a comma where I said put together as radio, meter then dummy load.
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Old 06-10-2015, 20:11   #7
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Re: Defective VHF or Antenna?

Really now, the first thing to do is to carry the hand held away a few hundred feet and repeat your test. It is free, and not much trouble. The other thing is to set up a sched with another boat at a few miles distance and contact on low power, then switch to high power. Again, free and not much trouble.

If it fails either of those tests, then get into the more complicated regimes as others have suggested.

Jim
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Old 06-10-2015, 21:30   #8
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Re: Defective VHF or Antenna?

If your handheld has a screw-on/off whip antenna you can just temporarily remove the antenna for your close-in tests. Don't try to transmit from the handheld, but this should significantly reduce the chance of overload when transmitting from your fixed VHF.

Or, has been suggested, get a few hundred feet away and have someone else transmit from the fixed VHF.
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Old 07-10-2015, 10:06   #9
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Re: Defective VHF or Antenna?

We keep a handheld and fixed (remote) at the helm that is normally to keep one on 16 while navigating around the commercial traffic and scan on the fixed. There are a few times when transmitted with the handheld on the same channel and received a great deal of feedback because, in the simplest of terms, it is transmitting the same as if you are looking into two mirrors facing each other. So, I would surmise the feedback is telling you it is working just fine.
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Old 07-10-2015, 10:23   #10
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Re: Defective VHF or Antenna?

Our new (to us) boat had an older VHF radio and antenna. Could not get anything from radio, so put in VHF from previous boat. Could receive, but not transmit. Replaced antenna, and things worked at high power but not low power. Turns out the antenna cable had corroded at each end. Took a few feet off and put new connectors at the mast head and at the radio and all works fine now. (Still with new antenna and newer radio)
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Old 07-10-2015, 10:37   #11
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Re: Defective VHF or Antenna?

If you are unfamiliar with the preceding test procedures (simple) ... may I suggest that you contact an experienced Amateur Radio operator in your local area. He will most probably help you determine what the problem is. I suggest someone with at least a General or Extra Class license. He also probably has the test equipment. We Hams like to help you guys out.
73
Joe W4CBJ St. Pete, FL
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Old 07-10-2015, 11:25   #12
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Re: Defective VHF or Antenna?

Just FYI, in the areas where I have kept my boat there is an easy radio check arrangement on Channel 27 sponsored by Boat US. Works very well for me to test my radios.

And I had problems with my fixed radio that required a $100 part fix via a repair service so perhaps not all radio problems require a complete swap out.
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Old 07-10-2015, 11:35   #13
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Re: Defective VHF or Antenna?

For about $25 you can buy an "emergency" antenna that comes with 20-50' of cable, for your main VHF. Unscrew the old cable, screw in the "emergency" antenna (used if the mast comes down and takes the usual one with it) and try again.


If it works that way, you know the problem is the ancient coax and antenna. Coax usually is not installed properly and will have a 5-10 year life. Antennas at 29 years old with coils in them, also can be past end of life. If either one of them is causing an SWR problem or shorting out at high power, your radio could be objecting.


Easy test, no real "cost" since the emergency antenna is one more piece of "Hope I never have to use it" to keep onboard.
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Old 07-10-2015, 12:00   #14
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Re: Defective VHF or Antenna?

Hi Jim

Both your antenna and VHF are likely to be working just fine.

I see so many replies and my experiences side with the replies about close proximity of receiver, when transmiting on high power.

A few hundred feet separation will not be enough. Need several miles separation is what my experience tells me.

Cheers

Julius
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Old 07-10-2015, 12:05   #15
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Re: Defective VHF or Antenna?

Separation will depend on the internal circuitry of your h/t. Some are crap, others are built at higher cost to reject excess signal strength and interference. I've had a good SH VHF on deck in the cockpit while someone was below transmitting from a 25W fixed VHF, and had no problems hearing both sides of their conversation. If you need "miles" of separation, you need a VHF that didn't come from the toy rack at WalMart.
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