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12-10-2015, 02:57 PM
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#1
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Senior Member
City: Blaine
Vessel Name: Slow Bells
Vessel Model: Marine Trader 38
Join Date: Nov 2013
Posts: 327
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question: fiberglass VHF antenna
My sailboats always had relatively small metal antennas at the top of the mast, but my trawler has a couple large fiberglass antennas. As I understand it, after 10 years or so, the sun's UV radiation does enough damage that the antennas need to be replaced. My question is: are you replacing the antenna because the fiberglass looks awful, or because the UV radiation somehow limits the antenna's ability to transmit and receive? Also, is there some way to determine when it is replacement time?
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12-10-2015, 03:19 PM
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#2
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Enigma
City: Slicker?
Join Date: Oct 2007
Posts: 16,563
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Greetings,
Mr. sbg. I suspect antennas are replaced because of the degradation of the fiberglass rather than failure to transmit or receive. I think an antennas performance is that it either works or it doesn't. Nothing in between. Mine were in pretty rough shape but a couple of coats of white paint cleaned them right up.
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RTF
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12-10-2015, 03:20 PM
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#3
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Guru
City: kemah
Join Date: May 2015
Posts: 1,135
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Strictly appearance. The antenna is a wire that run inside of the fiberglass.
But... The exterior coating can degrade so much that you get itchy after touching it.
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12-10-2015, 03:36 PM
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#4
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Senior Member
City: Toronto
Join Date: Nov 2015
Posts: 271
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Quote:
Originally Posted by RT Firefly
Greetings,
Mr. sbg. I suspect antennas are replaced because of the degradation of the fiberglass rather than failure to transmit or receive. I think an antennas performance is that it either works or it doesn't. Nothing in between. Mine were in pretty rough shape but a couple of coats of white paint cleaned them right up.
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RTF, I have somewhat similar dilemma.
During delivery of our boat by the broker, they broke both our 8' fiberglass antennas clearing a bridge (?) I did not pick up on that until they were gone so it's my loss. I was thinking of just replacing them both with Sailboat type antennas for aesthetic reasons if anything. I am aware of the loss of Gain with the shorter antennas but we have an arch above flybridge and that's where they would go, out of sight & mind. You appear a Trawler veteran, what you think ? or anyone else .. ? cheers Frank B.
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12-10-2015, 03:36 PM
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#5
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Moderator Emeritus
City: St. Marks, Florida
Vessel Name: Morgan
Vessel Model: Gulfstar 36
Join Date: Sep 2012
Posts: 3,673
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Quote:
Originally Posted by what_barnacles
Strictly appearance. The antenna is a wire that run inside of the fiberglass.
But... The exterior coating can degrade so much that you get itchy after touching it.
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Exactly. In addition, some corrosion around connections can degrade the signal, and to some degree corrosion goes with age. A new antenna is pretty cheap (compared to most boat things, I mean).
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John
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12-10-2015, 03:40 PM
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#6
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Moderator Emeritus
City: St. Marks, Florida
Vessel Name: Morgan
Vessel Model: Gulfstar 36
Join Date: Sep 2012
Posts: 3,673
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Quote:
Originally Posted by Ex Sailor
RTF, I have somewhat similar dilemma.
During delivery of our boat by the broker, they broke both our 8' fiberglass antennas clearing a bridge (?) I did not pick up on that until they were gone so it's my loss. I was thinking of just replacing them both with Sailboat type antennas for aesthetic reasons if anything. I am aware of the loss of Gain with the shorter antennas but we have an arch above flybridge and that's where they would go, out of sight & mind. You appear a Trawler veteran, what you think ? or anyone else .. ? cheers Frank B.
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As just a general statement, the longer the antenna, the better the signal. That said, most likely the little 1/4-wave antennas would serve you just fine, especially since you can put them up high.
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John
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12-10-2015, 04:52 PM
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#7
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Veteran Member
City: WIXOM
Vessel Name: INCOGNITO
Vessel Model: 34 MARINE TRADER
Join Date: Dec 2015
Posts: 31
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Paint w/ non-metal pigment white paint to contain the itchys
__________________
Mike Koski
32' Marine Trader........... 34' Marine Trader
" Curvaceous "............... " Incognito "
Newport, MI ................. Marathon, FL
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12-10-2015, 05:17 PM
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#8
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Guru
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,870
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Quote:
Originally Posted by what_barnacles
Strictly appearance. The antenna is a wire that run inside of the fiberglass. .
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It's a wire or a brass "element" (rod). Regardless, it's what's inside of the fiberglass tube that makes it work. You can paint the outside, just don't use paint with metal in it.
Or, buy a new one.
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12-10-2015, 05:24 PM
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#9
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Moderator Emeritus
City: St. Marks, Florida
Vessel Name: Morgan
Vessel Model: Gulfstar 36
Join Date: Sep 2012
Posts: 3,673
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Quote:
Originally Posted by WesK
You can paint the outside, just don't use paint with metal in it.
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Uh, yeah!
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John
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12-10-2015, 05:30 PM
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#10
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TF Site Team
City: Paris,TN
Vessel Name: Slo-Poke
Vessel Model: Jorgensen custom 44
Join Date: Jan 2013
Posts: 3,749
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Can I cut about 6" off and antenna still be good .I have to lay it down just a little to get under cover .
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Marty
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12-10-2015, 05:58 PM
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#11
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Guru
City: kemah
Join Date: May 2015
Posts: 1,135
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just be sure to cut it off the bottom.
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12-10-2015, 06:08 PM
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#12
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TF Site Team
City: Paris,TN
Vessel Name: Slo-Poke
Vessel Model: Jorgensen custom 44
Join Date: Jan 2013
Posts: 3,749
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It's 8 ft . Think I'll just get a 6 ft .
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Marty
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12-10-2015, 06:48 PM
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#13
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Guru
City: Sitka
Vessel Model: Transpacific Marine Eagle 32
Join Date: Dec 2014
Posts: 519
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I believe the antennas are pre tuned and cutting off a section may degrade the signal. I would not mess with safety equipment.
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12-10-2015, 07:00 PM
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#14
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Guru
City: Southern Maine
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 2,717
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Quote:
Originally Posted by Pack Mule
Can I cut about 6" off and antenna still be good .I have to lay it down just a little to get under cover .
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Or, just use a mount like this where it's easy to reach and lay it down before docking:
Even if you don't use the radio much, you do want to maximize its range in case you ever need it in an emergency.
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12-10-2015, 07:15 PM
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#15
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Senior Member
City: Maryville, TN
Vessel Name: malu lani
Vessel Model: Albin 27 FC
Join Date: Apr 2014
Posts: 113
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The antenna is cut to a specific length to match the frequency of your transmitter . It can be a 1/4 wavelength,1/2, or full wavelength of that frequency range, but DON'T cut it to a convenient length or your signal can be severely degraded. If a 1/2 wavelength is too long, just get a 1/4 wavelength unit. After that, the only thing that affects your signal is the height and the connectors, (including the coax cable). Ben
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12-10-2015, 07:18 PM
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#16
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Guru
City: Melbourne, FL
Join Date: Dec 2014
Posts: 1,731
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Quote:
Originally Posted by what_barnacles
just be sure to cut it off the bottom.
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If you cut an antenna off, it will change the optimum wavelength and the SWR. If you use an antenna tuner, it will have to correct that loss in the tuner.
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12-10-2015, 07:40 PM
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#17
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Guru
City: kemah
Join Date: May 2015
Posts: 1,135
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Quote:
Originally Posted by stubones99
If you cut an antenna off, it will change the optimum wavelength and the SWR. If you use an antenna tuner, it will have to correct that loss in the tuner.
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missed the sarcasm huh?
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12-10-2015, 07:44 PM
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#18
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Master and Commander
City: Vallejo CA
Vessel Name: Carquinez Coot
Vessel Model: penultimate Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 12,559
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Have no problem with fiberglass degradation. A "sailboat" anntennae works fine with my motor vessel.
__________________
Kar-KEEN-ez Koot
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12-10-2015, 08:25 PM
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#19
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TF Site Team
City: Saltspring Island
Vessel Name: Retreat
Vessel Model: C&L 44
Join Date: Nov 2007
Posts: 5,663
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The "Sailboat"antenna has a pattern that allows it to be almost as efficient in transmitting and receiving when heeled over as it is when the boat is standing upright. The longer fibreglass antenna has a pattern that is much narrower, so is not appropriate on a sailboat.
On a powerboat, there will be a difference in signal strength between the two. The longer one will have a stronger signal.
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12-10-2015, 08:49 PM
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#20
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Guru
City: Maine Coast
Vessel Name: Tortuga
Vessel Model: Nunes Brothers Raised Deck Cruiser
Join Date: Feb 2015
Posts: 889
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The sailboat antenna is also acceptable because it is up high. Since VHF is line of sight, higher means longer range. For example my antenna on my sailboat is 50' above the water at its base.
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