I mentioned before my new boat's marine antenna is GONE. As in broke slap off and a piece of white rg58 is wrapped around the mount. Today I notice AM/FM reception fade, start looking---there's a goofball 2 into 1 box lookin like it's dual function antenna---i.e. junk.
How do I solve this? I can fix any commercial 2way but dunno jacksquat about marine/AMFM dualpurpose antenna stuff... ;(
HELP!?
I think this is hokey???
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Jonathan KC8RYW
- Posts: 1747
- Joined: Fri Dec 28, 2001 4:00 pm
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RadioSouth
- Batboard $upporter
- Posts: 2884
- Joined: Mon Sep 03, 2001 4:00 pm
Probably just a splitter to get you FM reception off your marine VHF antenna. I've seen these boxes in the marine store and they were not specific to a antenna, will work with any marine antenna. Being my boat is fiberglass I've run about a 4 foot wire out the back of the stereo up the wall in the cabin and it works great. I guess being out on the briny provides a good ground plane. The other thing is the standard for most pleasure boats has been those 8' fiberglass sticks, maybe that obtrusive length is how it got broken ? After reading an antenna test in PowerBoat reports I noted how the 4' fiberglass sticks as well as the 36" base loaded
stainless steel antennas perform. (pretty darn good). I switched out to a
Shakespeare 36" stainless steel base loaded whip which works well and besides being 5' shorter the top 90% is a metal whip with quite a bit of springiness, probably will never break this one off !
stainless steel antennas perform. (pretty darn good). I switched out to a
Shakespeare 36" stainless steel base loaded whip which works well and besides being 5' shorter the top 90% is a metal whip with quite a bit of springiness, probably will never break this one off !
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hfitzgerald
- Posts: 288
- Joined: Sat Jun 01, 2002 7:00 pm
Fiberglass marine antennas.
From my past experience, with the local MSS, antenna designers, and Comtelco, a typical VHF Marine fiberglass antenna is 1/2 wave, -thus allowing it to function without a ground plane since a half wave resonates freely without one (1/4 and 3/4 would require a ground plane). Longer and Loaded antennas can perform better, but the standard antenna that's on 95% of the boats out there is 1/2 wave, and almost no different than a commercial fiberglass antenna.
Back when quantities were fewer and quality was better, a fiberglass marine antenna would be injected with foam for complete water protection. However, the foam expanded at different rates every time and the dielectric constant would shift depending on concentrations of foam and how it set up. -this lead to the antenna shifting frequencies outside of tolerable limits. On the average, one out of four injected marine antennas were built sucessfully. The rest were scrapped or sold for other applications (where the frequency matched). Today, most marine antennas are not injected and have some sort of opening in the base to allow condensation and moisture to drain out.
A popular application in our unit is to buy a matching set of antennas from a manufacturer like Comtelco, and have one cut for VHF Marine, and the other is cut for VHF Amateur or VHF Law Enforcement, etc. Having a custom built fiberglass antenna is almost the exact same price as a fiberglass marine antenna if you know where to get them. When mounted on opposing sides of your stern, they look very cool on your boat and nobody knows wiser until you light up the strobes and the siren.
Back when quantities were fewer and quality was better, a fiberglass marine antenna would be injected with foam for complete water protection. However, the foam expanded at different rates every time and the dielectric constant would shift depending on concentrations of foam and how it set up. -this lead to the antenna shifting frequencies outside of tolerable limits. On the average, one out of four injected marine antennas were built sucessfully. The rest were scrapped or sold for other applications (where the frequency matched). Today, most marine antennas are not injected and have some sort of opening in the base to allow condensation and moisture to drain out.
A popular application in our unit is to buy a matching set of antennas from a manufacturer like Comtelco, and have one cut for VHF Marine, and the other is cut for VHF Amateur or VHF Law Enforcement, etc. Having a custom built fiberglass antenna is almost the exact same price as a fiberglass marine antenna if you know where to get them. When mounted on opposing sides of your stern, they look very cool on your boat and nobody knows wiser until you light up the strobes and the siren.