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Old 07-10-2015, 12:11   #16
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Re: Defective VHF or Antenna?

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Originally Posted by JD.M View Post
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
Just as a swag or maybe more a wag and I hope it is wrong. It could be the coax has a problem with insulation breaking down with age.
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Old 07-10-2015, 12:21   #17
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Re: Defective VHF or Antenna?

I our area north of Boston channel 27 has an automatic radio check feature. Perhaps there is a similar set up near you.
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Old 07-10-2015, 12:25   #18
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Re: Defective VHF or Antenna?

It is and isn't just a matter of "age". The insulator between the coax jacket and core can be solid plastic, various plastic foams, etc. The solid plastic is of course not going to absorb water, and retain its shape and thickness best. The foams have better electrical characteristics--but often absorb water, which negates that.


And then, no matter which coax you use (thicker being stronger, but more weight aloft and more money), there's the matter of installation. If you just "hang" it in the mast, is stretches over time, just like hanging up a strand of play-doh. As it stretches, the insulation compresses and the electrical properties go down the toilet again.


So some clever soul zipties the coam ever three feet. Except, the zipties also compress the cable and it still breaks down, even if it doesn't stretch as much.


And unless you hired Hinckley and gave them your Amex Black card...no one used "Chinese finger traps" aka cable sleeves to secure the cable. These look kinda like big mesh heart artery stents, about six inches of the mesh snugs tight around the coax and grabs it without putting on a point load like a zip-tie would. In real life you probably will never see one.


So one way or the other, even if the cable ends were properly sealed and nothing chafed the outer jacket, I think you'd find most radio operators would suggest that even the best coax needs to be properly replaced every 5-10 years.


29 years? It will cost you more for test equipment to verify the cable and antenna are working right, than to just replace 'em. Not just SWR, but efficiency and performance too.
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Old 07-10-2015, 12:38   #19
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Re: Defective VHF or Antenna?

Most times if the radio will power up and receive it's ok. Problems are usually in the antennas and or coax.
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Old 07-10-2015, 12:58   #20
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Re: Defective VHF or Antenna?

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Originally Posted by SariTimur View Post
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

This is good advice-- I have seen numerous instances where water has entered the coax and resulted radio problems. This and poor connections represent the majority of marine VHF problems I've seen--- other than diodes cooked when the Color blind crew mix up red and black.

A SWE meter (standing wave ratio) is a super tool for tracking these issues down.

An
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Old 07-10-2015, 16:27   #21
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Re: Defective VHF or Antenna?

Wow, thanks to all for their input.

After thinking about it more, I know I have successfully tested the main VHF in the past using the handheld while standing right next to it.

I was at the boat today (haul out day) and was prepared to ask some of the marina staff to help me with a longer distance test. But before leaving the boat, I just tried to raise the marina and got the "beep"/squeal just keying the mike on high power. No beep/squeal on low power. There was no one available from the marina (or other boat owners for that matter) who were available to help test further, but when I heard the beep/squeal on high power just keying the mike and no beep/squeal on low power, I'm pretty sure it's not a distance issue.

I forgot to mention that I have an antenna splitter in the loop that also feeds the FM stereo from the masthead -- gets really good reception!

I think my best bet is to try disconnecting the antenna splitter (it's right next to the radio) and see if it's the issue. If not, I'm hoping I might be able to take the radio somewhere nearby and have it tested. The boat is seriously for sale, so I don't want to spend money on an emergency antenna...that's about half the price of just replacing the existing antenna whip, if I remember correctly.

I do have an SWR meter from my CB days, but no dummy load so I don't if that would be helpful or not.

Again, thanks to all.

Jim
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Old 07-10-2015, 17:25   #22
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Re: Defective VHF or Antenna?

Quote:
Originally Posted by JD.M View Post
Wow, thanks to all for their input.

After thinking about it more, I know I have successfully tested the main VHF in the past using the handheld while standing right next to it.

I was at the boat today (haul out day) and was prepared to ask some of the marina staff to help me with a longer distance test. But before leaving the boat, I just tried to raise the marina and got the "beep"/squeal just keying the mike on high power. No beep/squeal on low power. There was no one available from the marina (or other boat owners for that matter) who were available to help test further, but when I heard the beep/squeal on high power just keying the mike and no beep/squeal on low power, I'm pretty sure it's not a distance issue.

I forgot to mention that I have an antenna splitter in the loop that also feeds the FM stereo from the masthead -- gets really good reception!

I think my best bet is to try disconnecting the antenna splitter (it's right next to the radio) and see if it's the issue. If not, I'm hoping I might be able to take the radio somewhere nearby and have it tested. The boat is seriously for sale, so I don't want to spend money on an emergency antenna...that's about half the price of just replacing the existing antenna whip, if I remember correctly.

I do have an SWR meter from my CB days, but no dummy load so I don't if that would be helpful or not.

Again, thanks to all.

Jim
Get rid of the splitter. I have no earthly idea what an SWR meter would tell you at this point? The antenna hasn't changed. You didn't have St Elmo's fire come in on you?
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Old 07-10-2015, 17:35   #23
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Re: Defective VHF or Antenna?

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Get rid of the splitter. I have no earthly idea what an SWR meter would tell you at this point? The antenna hasn't changed. You didn't have St Elmo's fire come in on you?
An SWR meter might tell you that a connector or cable has opened up, or shorted. If you know what you're doing it can tell you if the coax has gone lossy (although lossy cable isn't likely to be the problem given the reported symptoms). Of course antennas can also go bad in time. Connections and wires corrode. It happens, and a SWR meter can help locate these problems.

But before the OP tries the SWR meter, there are simpler tests that have been suggested. Here's a link to SeaTow's automated VHF test -- perhaps they have a test station in the OP's area: https://www.seatow.com/tools-and-edu...ed-radio-check
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Old 07-10-2015, 17:51   #24
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Re: Defective VHF or Antenna?

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Originally Posted by Paul Elliott View Post
An SWR meter might tell you that a connector or cable has opened up, or shorted. If you know what you're doing it can tell you if the coax has gone lossy (although lossy cable isn't likely to be the problem given the reported symptoms). Of course antennas can also go bad in time. Connections and wires corrode. It happens, and a SWR meter can help locate these problems.

But before the OP tries the SWR meter, there are simpler tests that have been suggested. Here's a link to SeaTow's automated VHF test -- perhaps they have a test station in the OP's area: https://www.seatow.com/tools-and-edu...ed-radio-check
Paul,

Your unfortunately right. From what he has described my guess would be corrosion although the coax beating around in the mast might be the worst case. I hope he finds it.
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Old 07-10-2015, 17:55   #25
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Re: Defective VHF or Antenna?

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I our area north of Boston channel 27 has an automatic radio check feature. Perhaps there is a similar set up near you.
Yeah, I'm envious. I checked the Seatow website while on Lake Huron and found out they haven't set up any stations nearby. They have one over on Lake Michigan, but that's quite a ways away. Seems like a great idea, though.
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Old 07-10-2015, 18:12   #26
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Re: Defective VHF or Antenna?

CB radio is an entirely differently frequency, so the SWR meters "just for CB" rarely will cover a marine VHF.


If you do a little web research, you can take two feet off an old coax cable and literally turn THAT into a properly tuned antenna. Or even a coat hangar or a heavy wire. Basically, you need to ground the outside of the coax connector on the radio, and jam a wire into the center hole, with that center wire being about 19-1/2" long. It won't be elevated--but it will be a properly "tuned" antenna. (A fast look on the web will get you relaxed about it.)


Most modern radios also cut back their output power if the SWR is excessive, to protect themselves. And many also "squeal" when they can't get enough power form the power cable. So it could be you've got a weak power connection, able to provide low power, but crapping out and dropping the voltage and making the radio squeal as it can't function without power on the high power setting.


If you're selling the boat...odds are the new buyer won't care or will want a new radio with AIS and DHC, so you might just say "There's a problem with the radio...I didn't fix it because I figured you would want one of the new ones anyway."
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Old 07-10-2015, 20:46   #27
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Re: Defective VHF or Antenna?

I would offer 3 possibilities as follows:

1) The DC wiring is either inadequate or has developed some high resistance due to corrosion or poor crimp.

2) The antenna and/or coax to the ICOM has been damaged.

3) The handheld is too close to the ICOM and is getting overloaded.

Reasoning:

1) A fixed VHF draws >6A at high power transmit but only about 1A at low power transmit. If the DC voltage sags during high power transmit you can get exactly this kind of weird squealing from a VHF radio.

2) If the coax has a short or open then the VHF can make strange squealing sounds due to the bad mismatch. The handheld can still hear the noise but other radios further away don't hear anything.

3) The handheld might be getting overloaded but this is my least favorite suspect. Most VHF radios are very immune to this.

How to test:

Ask a friend to contact you when their boat is about 2 miles then 1 mile away. Ask them how it sounds on low power (1W) and then switch to high power (25W). If they can hear you fine on both settings then your handheld could be the issue. If they can hear you fine at low power but hear squealing at high power then suspect the DC power feed. If they can't hear you on low power (1W) at 2 miles then you would suspect the coax/antenna.
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Old 08-10-2015, 12:39   #28
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Re: Defective VHF or Antenna?

JD,
Sorry I missed this thread earlier....but, good news is that the last two posts, #26 from Hellosailor and #27 from transmitterdan, have given you the best answers!!
Read them over again, and use them as the most likely / probable solutions!!


And, in the vein of DC power issues....it is often overlooked, because most sailors will test voltages on receive rather than when transmitting (and the voltage drops at the square of the current drawn, so twice the current is 4 times the voltage drop, etc.) and it is this voltage at the radio not at the breaker panel, when transmitting that is critical!
Understand that checking voltage at the panel / at the breaker (where it might be okay), but not at the radio (where it might not be!), can be a fool's errand!



Fair winds!

John
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Old 08-10-2015, 13:00   #29
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Re: Defective VHF or Antenna?

It has been a long time. I didn't think an SWR was frequency sensitive maybe power?
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Old 08-10-2015, 19:30   #30
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Re: Defective VHF or Antenna?

Cadence,

I am unsure what you are asking. Try again and I will try to help.
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