VHF radio trouble - SailNet Community

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  #1  
Old 10-12-2007
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VHF radio trouble

Hi all,

My recently purchased used boat came with a Raymarine VHF and a nice masthead antenna. Now, I admit to being a radio novice.... Here is the problem. When I turn the unit on, all I hear is static until I turn the squelch all the way down to silence it. I have never heard any conversation through the static. So, obviously something isn't working. How does one troubleshoot the radio?

One item that looks like an issue is the connector between the deck and the mast for the antenna cable. It's a coax cable screw-in terminal and it looks slightly corroded. Is there a way to connect the radio to a "makeshift" antenna in the cabin to at least test the radio? Any specific tests that can be done with a basic multimeter to test the antenna cable? (Ohms of resistance to look for... etc...)

Any help is greatly appreciated
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Old 10-13-2007
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Quote:
Originally Posted by SiXeVeN View Post
When I turn the unit on, all I hear is static until I turn the squelch all the way down to silence it.
All the way up? (More squelch = up, not down.) Usually one can achieve squelch at much less than all the way up.

Quote:
Originally Posted by SiXeVeN View Post
I have never heard any conversation through the static. So, obviously something isn't working.
Possibly. I assume you've listened to channel 16 for a lengthly time?

Quote:
Originally Posted by SiXeVeN View Post
How does one troubleshoot the radio?
Troubleshooting the radio, itself, requires knowledge and test equipment.

Quote:
Originally Posted by SiXeVeN View Post
One item that looks like an issue is the connector between the deck and the mast for the antenna cable. It's a coax cable screw-in terminal and it looks slightly corroded.
That is bad. That could definitely be a problem.

Quote:
Originally Posted by SiXeVeN View Post
Is there a way to connect the radio to a "makeshift" antenna in the cabin to at least test the radio?
Yes. They make emergency antennas. You should have one anyway.

Quote:
Originally Posted by SiXeVeN View Post
Any specific tests that can be done with a basic multimeter to test the antenna cable? (Ohms of resistance to look for... etc...)
Yes. Resistance (DC) between the coax center conductor and shield, when the antenna's connected, should be very close to zero (a few ohms, at most, depending on coax length). With no antenna connected, it should be infinity.

Jim
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Jim,

Thanks for the reply! Squelch... Yes, the knob is at its maximum! Obviously not correct.

I will check the resisitance of the antenna... I still expect that is the problem.
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Old 10-13-2007
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Quote:
Originally Posted by SiXeVeN View Post
Hi all,



Any help is greatly appreciated
It is almost always the antenna.
Get a little ducky or borrow one and try it.
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Old 10-13-2007
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Quote:
Originally Posted by SiXeVeN View Post
I have never heard any conversation through the static. So, obviously something isn't working. How does one troubleshoot the radio?


Turn to WX (I guess your Raymarine has the weather band) There is a continuous broadcast. If you don't hear the weather you have an antenna problem. The corroded connector is the likely villain. Don't buy a connector from Radio Shack, but from a marine shop. The RS connectors are not designed to be exposed to marine conditions.

Also, when your mast is down for the season, check on the condition of the cable inside the mast. If it is hard to bend, the cable is likely corroded and needs to be replaced.

After replacing your coax connector at the deck, find a way to hold the cable in a loop so that water running down the cable drips off the bottom of the loop before it reaches the new connector. That will help to extend its life. Find a way to keep most of the water off the connector. Even a plastic bag wrapping it and sealed to the cable above and below with some electrical tape will help. With precautions like these a coax connector can last a long time.
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Old 10-13-2007
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Thanks all!

I will give the antenna cable a good bit of examination tomorrow! I'll also see if I can find an emergency antenna to check out the radio function as well.
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Since you are reasonably sure you have a coax / connector problem when you try to receive, DON'T try to transmit, esp at high power...that could compound your problem enormously...read that 'EXPENSIVELY'. There aren't many things that can kill your transmitter but that's one of them.
Howard Keiper
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Old 10-13-2007
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Get one of these for testing then save for emergencies:
http://shop.sailnet.com/product_info.php/products_id/787?search=1&keywords=vhf%20antenna
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Old 10-15-2007
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Ok everyone, I checked the resistance of the antenna... It was off the chart. I measures 328 Ohms!!! A subsequent cleaning of the connectors got me down to about 90. Basically I need to replace the connectors...

I can now recieve the Wx and hear conversation on 16 but it is VERY static filled and almost impossible to understand. If I adjust squelch to lose the static then I lose everything. I wonder if I might have a larger problem than just high antenna resistance. Would a 90 Ohm resistance also cause static? I would surmise that high resistance would limit my ability to transmit or recieve but would it make the signal dirty? BTW, there were no other electronic devices active except the VHF.

Last edited by SiXeVeN; 10-15-2007 at 04:22 PM.
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You already got good advice, though I can understand that with so many voices you may have difficulty sorting them out.

1. Disconnect your antenna at the radio.

2. Plug in another antenna...an emergency antenna, or a temporary one you make up.

3. See if you can receive WX. See if the static disappears.

4. If you receive OK and without static, your rig is probably OK.

5. Replace the connectors and coax. Make sure all connections are clean and tight.

Don't fool around with this anymore. If you can't do it, call on a professional or a ham to do it for you.

Bill
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