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  Useful Life of VHF Antenna, Feed Line

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Author Topic:   Useful Life of VHF Antenna, Feed Line
Frank O posted 04-25-2012 10:03 PM ET (US)   Profile for Frank O   Send Email to Frank O  
I'm getting ready to remove the T-top from my 1995 Outrage 21, and am giving some thought to the VHF antenna and coaxial cable. Normally I don't think of these as being components with a notably limited lifetime, but given that they've been on the boat for 17 years I wonder if they might be considered candidates for replacement. The antenna, for example, looks like it's developed a bit of a bend over the years. Does performance of such components tend to decline after long periods of weather exposure?

jimh posted 04-26-2012 12:53 PM ET (US)     Profile for jimh  Send Email to jimh     
The useful life of an antenna is related to the quality of its manufacturing. In a marine environment the motion, saltwater, and sunlight can rapidly age poorly made antennas.

Coaxial cable lifespan is highly dependent on the material used for the outer jacket. Only Type-II or Non-Contaminating vinyl outer jackets have a long life. Coaxial cable made with contaminating vinyl outer jacket will tend to develop increased attenuation with age as the vinyl jacket contaminates the outer shield conductor. Most of the coaxial cable sold with marine antennas that I see is, unfortunately, the contaminating type. The antenna that I recommend, the GAM Electronics antenna, uses military grade RG-58C/U coaxial cable with a non-contaminating jacket.

The reality of the marine environment is the antenna will likely fail before the coaxial cable degrades from contamination of the vinyl in the outer jacket. Since most of these antennas have a captive feed line that cannot be replaced, this means you will throw out the feed line when you install a new antenna. By the way, that is another benefit of the antenna I recommend, the GAM Electronics antenna has a detachable feed line which can be replaced separately from the antenna.

See:

http://continuouswave.com/whaler/reference/VHFAntenna.html

Frank O posted 04-29-2012 03:32 PM ET (US)     Profile for Frank O  Send Email to Frank O     
Jim, thanks for the pointer to the helpful article. My antenna is seeming tired, so I'm game to give a GAM SS-2 a try. I gather that the antenna, ADAP-II base and Shakespeare 498 extension mast should connect up to my ratcheting mount, which I'm guessing is probably a Shakespeare:

http://www.inkbox.net/whaler/parts/antenna-mount.jpg

Do you use anything like a dielectric paste or other sealant when you assemble the components?

While I've spent many years around soldering irons and guns, I've never had occasion to hook up coax to a PL-259 connector. I'll have to do some research on the right way to accomplish that.

contender posted 04-29-2012 04:38 PM ET (US)     Profile for contender  Send Email to contender     
Frank: Quit wasting your time a and go purchase a new antenna and cable (comes with the antenna) You may need it one time to save yourself and others, I like the shakespeare 8ft galaxy models, black does not show the dirt
Frank O posted 04-29-2012 05:48 PM ET (US)     Profile for Frank O  Send Email to Frank O     
Contender, actually that's what I am doing -- but instead of going with a Shakespeare, I thought I'd try the antenna that Jim chose after researching the topic. I'll be interested to see how it performs. I haven't run any precise tests, but I have the feeling I haven't been getting out a lot of signal with my nearly 20-year-old existing antenna.

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