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?

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.

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.

RT Firefly said:

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.

what_barnacles said:

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).

Ex Sailor said:

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.

Paint w/ non-metal pigment white paint to contain the itchys

what_barnacles said:

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.

WesK said:

You can paint the outside, just don't use paint with metal in it.

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Uh, yeah!

Can I cut about 6" off and antenna still be good .I have to lay it down just a little to get under cover .

just be sure to cut it off the bottom.

It's 8 ft . Think I'll just get a 6 ft .

I believe the antennas are pre tuned and cutting off a section may degrade the signal. I would not mess with safety equipment.

Pack Mule said:

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.

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

what_barnacles said:

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.

stubones99 said:

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?

Have no problem with fiberglass degradation. A "sailboat" anntennae works fine with my motor vessel.

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.

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.

Greetings,
Mr. ES. Lots of good advice here. I'm the last person you should ask about electronics. I know a bit about paint, hence my advice to paint a fuzzy aerial.

Just how much time do you spend off shore talking to other boats 50 miles away?

For most inshore apps the base loaded SS whip is fine.

I sanded and painted my fuzzy AM/FM and VHF radio antenna with a one part epoxy 3 years ago. They still look new.

koliver said:

... there will be a difference in signal strength between the two. The longer one will have a stronger signal.

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The 36" antenna is 3 dB vs the 8' is 6 dB.

...An antenna’s dB rating (or antenna gain) indicates the apparent increase in transmitting power due to its ability to focus energy...A gain increase of 3dB means a doubling of signal strength: 6dB is a fourfold increase, and 9dB is an eightfold increase. The actual watts transmitted doesn’t increase; it’s just that the power is concentrated, much like a reflector on a flashlight, in a more concentrated beam. Therefore, a radio with a 6dB antenna will sound like it has a larger transmitter than the same radio with a 3dB antenna...

FF said:

Just how much time do you spend off shore talking to other boats 50 miles away?.

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For most of us, not much time, but there may be a time when it's very important to communicate to another station 50 miles away. I think it's important to think of our VHF transceivers as safety equipment, not entertainment. We should aim for the best we can practically accomplish.

Digital antennas is also a option for a replacement if needed. They are wood epoxied and painted. Just wax a few times a year, always looks new and don't degrade. Very well made. They are located in Florida. I had 4 for over 10 years, looked great and looked like new the day I sold the boat.


Sent from my iPad using Trawler Forum
Capt. Don

FF said:

Just how much time do you spend off shore talking to other boats 50 miles away?

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Hopefully, never. But that one time you need help, and it's 50 miles away, you'll probably be glad you didn't go cheap on the antenna.

I was wondering, how many of you only have one radio?

I have 4, two on 8' whips, one on the mast head "sailboat" antenna and of course a hand held with antenna adapter if needed to use in a pinch.

I do use 2 radios at a time in the wheel house, separate channels of course.

I have a back up near the helm but closer to the "first officer" in case the helmsman is too busy, bridge tenders respond nicer to a softer voice anyway.

IntervaleII said:

Digital antennas is also a option for a replacement if needed. They are wood epoxied and painted. Just wax a few times a year, always looks new and don't degrade. Very well made. They are located in Florida. I had 4 for over 10 years, looked great and looked like new the day I sold the boat.


Sent from my iPad using Trawler Forum
Capt. Don

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Just to be clear, "Digital" is a brand of antenna, not a type or technology. They are built the same as any other VHF antenna. They seem to be of high quality but the technology is the same. They won't work any better.

SCOTTEDAVIS said:

I was wondering, how many of you only have one radio?

I have 4, two on 8' whips, one on the mast head "sailboat" antenna and of course a hand held with antenna adapter if needed to use in a pinch.

I do use 2 radios at a time in the wheel house, separate channels of course.

I have a back up near the helm but closer to the "first officer" in case the helmsman is too busy, bridge tenders respond nicer to a softer voice anyway.

Click to expand...

I have one fixed and one hand held. That's two.

Also two cell phones for calling marinas, etc.