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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance
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  #11  
Old 06-07-2013
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Re: VHF Antenna Masthead Installation Questions

Quote:
Originally Posted by Lateen Luffer View Post
If you have any doubt as to whether there's an antenna, DO NOT TURN ON THE RADIO. Deltaten was right, it could damage your radio's finals. Unplug the antenna lead from the back and test the center wire and threaded outer contact of the co-ax cable. If you have somewhere around 50 ohms of resistance, there is likely an antenna somewhere. If you want to get fancy you could use a thing called a standing wave ratio meter, or SWR. That will tell you neat stuff like whether the antenna is 'trimmed' correctly to optimize power transmission or in your case, whether there's any antenna at all! Good luck! ~LL
This is not all together true! Many VHF antennas will look like either an open circuit (Ohm meter reads infinity to several hundred K ohms) or a dead short (near zero ohms). If your volt-ohm meter reads anywhere near 50 ohms, the feed line, antenna or both are likely bad. Either that or a dummy load is connected.

Most modern radios will not be harmed by transmitting into an open or shorted antenna for a few seconds.

Now if you know someone with an antenna analyzer, a SWR bridge or a forward / reflected power meter, you may be able to find out whether the antenna and feed line are good.

If the feed line is old or water contaminated, the SWR and reflected power may look great. The problem with water damaged coax/feed line is almost all of the power gets turned into heat before it gets to the antenna.
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Old 06-07-2013
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Re: VHF Antenna Masthead Installation Questions

Jxvega,

Welcome to the Irwin community, be sure to check out the owner group on Yahoo.

Going up the mast in a bosun's chair is not that hard if you can handle heights and have someone to do the cranking. If you are indeed missing the antenna but have a masthead connection with good cabling it's a simple "screw in the antenna" job that will take less time to do that it takes cranking you up.
Borrow a chair and a cranker, follow the advice of someone at the marina who knows what going aloft is about, check it out and don't forget to take pictures while you are up there.
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  #13  
Old 06-08-2013
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Re: VHF Antenna Masthead Installation Questions

You will most probably will not read 50 ohms for the antenna. If there is any type of resistance (not open circuit) that means you have an antenna. A bosuns chair is the simplest method if you do not have the antenna.

A wireless will send messages with any antennena, but for a good receipt is possible if you mount it the highest possible.
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Re: VHF Antenna Masthead Installation Questions

I was able to check out the vhf radio and there is a cable connected to the unit. I keyed the mic and was able to communicate with my handheld vhf. I tried to see if I can make out the antenna and it seems there is one that is part of the wind vane, but I'm not entirely sure.
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Old 06-12-2013
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Re: VHF Antenna Masthead Installation Questions

Maybe you're ok. But on the other hand I can say from experience that you can talk to a handheld with a broken antenna. My cabling was busted at the deck fitting and I could talk to people nearby no problem. I then set off on a cruise and soon saw all the harbor activity fade away.
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Re: VHF Antenna Masthead Installation Questions

Thanks for the insight. I'm going to have to try some range testing.
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Re: VHF Antenna Masthead Installation Questions

Everyone, thank you for the responses!
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