can a vhf aerial wear out?

[roam]

our boat has a Danish CelWave CX4 fibre glass aerial fitted. i have no idea how old it is - it may even be original (20 + years) as the boat was originally kept in Sweden and then Germany.

We have just fitted a 2nd vhf aerial as we needed a dedicated one for the AIS transponder. I am getting considerably better coverage with the new aerial (Glomex SS whip) than the old Celwave. i have replaced the co-ax on the original antenna and got no improvement in performance. the connections on the aerial look clean and undamaged.

We are currently in India and choice of new antennas is very limited - to 1 type - unbelievably another CelWave CX4! i don't want to spend money if i don't think that the performance will improve. does an aerial have a limited life?

any thoughts?

thx

 

[Bilgediver]

our boat has a Danish CelWave CX4 fibre glass aerial fitted. i have no idea how old it is - it may even be original (20 + years) as the boat was originally kept in Sweden and then Germany.

We have just fitted a 2nd vhf aerial as we needed a dedicated one for the AIS transponder. I am getting considerably better coverage with the new aerial (Glomex SS whip) than the old Celwave. i have replaced the co-ax on the original antenna and got no improvement in performance. the connections on the aerial look clean and undamaged.

We are currently in India and choice of new antennas is very limited - to 1 type - unbelievably another CelWave CX4! i don't want to spend money if i don't think that the performance will improve. does an aerial have a limited life?

any thoughts?

thx

There could have been water ingress into the base where there could be a matching transformer. Also different antennas have different performances.

Try comparing its performance to a 1/4 wave antenna . You can make one of these either by cutting back the shielding of coax for about 17 1/2 inches and supporting the exposed centre conductor vertically or soldering a 17 1/2 inch length of stiff wire to the centre core of coax . The shielding is not connected at the antenna end. This also works fine as an emergency antenna. If you Cellwave is noticeably worse than the 1/4 wave then it is not performing.

 

[john_morris_uk]

The short answer is no - a VHF antenna does not wear out. However if it is not performing as well as the new antenna there is something wrong. You have done the correct thing in checking the co-ax and connections. I assume that you have put the connectors on accurately and soldered them? If that is the case (or you are using the same co-ax for each antenna then there is something wrong inside the old antenna. It will almost certainly be corrosion due to water ingress - although it might conceivably be a fractured wire or joint inside which has failed due to the years of wobbling about in the wind etc.

Good luck with the new antenna - you could always order one mail order from UK - I know that many chandlers (eg Andy at yachtparts in Plymouth - no connection only a customer) post overseas regularly.

 

[Bosun Higgs]

Yes - sadly they can. In use all the electrons are rushing up and down the aerial at 160mHz and sooner or later this starts to wear a groove in the metal. I've had some success repairing them by applying plastic metal into the grooves with tweezers but the last one I did only worked thereafter on the Home service. And when I called Swansea coastguard in the middle of the Archers it caused endless confusion and Nigel Pargitter to fall off the roof.

So maybe best get a new one or alternatively stick a metal coat hanger into the socket

 

[Twister_Ken]

. And when I called Swansea coastguard in the middle of the Archers it caused endless confusion and Nigel Pargitter to fall off the roof.

And a big disappointment that was. With all the well-trailed hullabaloo I was expecting an announcement to redevelop Ambridge as an International Airport, Tony to be discovered to be a major drugs dealer and David to sell Brookfield as the site for a nuclear power station.

Whoops, thread drift, although I expect Eddy could get hold of some hooky VHF aerials.

 

[savageseadog]

I was hoping to find a disincentive to all those radio checks

 

[Salty John]

On a fibreglass whip antenna the radiating elements are encapsulated within the fibreglass shaft. Over time these elements, (usually brass on better aerials or it could be just stripped back coax on cheap ones), can fatigue with the constant motion and break. That's why I prefer a SS whip.

CelWave do a SS whip version for 156 - 162mHz, maybe that's available? If not the fibreglass version would be better than your, apparantly, damaged one.

 

[mustntgrumble]

"wear out" - or just stop working properly...

Technical explanations having already been presented - a recent experience was that VHF & newly installed AIS appeared to be working, but not much traffic. I'd just moved to a new cruising area & I just thought it was quiet. Then I noticed Coastguard transmissions were clearer on handheld than (masthead aerial) vhf, and tho I could eyeball the Irish ferry it was decidedly stealthy on the AIS.

Unplug aerial = reception no worse. Replace masthead aerial (& cable) = RESULT!! ie ships all over the AIS screen, & constant VHF chat (I say, radio check radio check)

 

[William_H]

Fibreglass VHF antena

If you are about ready to buy a new antenna then it is not that hard to open up the f/g one to check for condition. As said failure of joints by fatigue from vibration or corrosion are the main failure modes.
The fibreglass is a thin tube glued usually into a metal socket at the base. Cut carefully around the f/g with a hacksaw. Don't cut deep. The f/g sheath will slide off exposing the innards.
To reassemble you need to pull the innards clear of the metal base and destructively remove the inch or 2 of f/g inside the base. Push the innards back into place and put the sheath over the top, back into the socket and glue in place. Hopefully the innards do not extend all the way to the top inside the sheath so a little shorter won't hurt.
As an alternative to cutting the sheath you could try a lot of heat to melt the glue of the sheath into the base. Enough hopefully to melt the glue but not the f/g.
As I said if you are going to buy a new one you have nothing to lose. good luck olewill

 

[roam]

it WAS the aerial

thanks all for your comments and advice.

i took the rubber stopper off the top end of the fibre glass tube, with a magnifying glass you can inspect the top end of the actual aerial. it was definitely showing signs of wear. when turned upside down a few flakes of metal came out.

so, i have replaced the aerial - easy since it was the same mast head fitting - but expensive at nearly 100 quid here in india with no cable (fortunately not needed).

i have tested both new aerials on the AIS and get very similar readings on both.

i can tick another job off the list!