VHF or AIS transponder aerial on a spreader?

[yoda]

Has anybody any first hand experience of putting either their VHF or AIS transponder aerial on a spreader? Does it suffer from blind spots caused by the mast or is the normal movement of the boat sufficient to make it a negligable effect?

Thanks

Yoda

 

[salar]

Has anybody any first hand experience of putting either their VHF or AIS transponder aerial on a spreader? Does it suffer from blind spots caused by the mast or is the normal movement of the boat sufficient to make it a negligable effect?

Thanks

Yoda

Both, and no effect.

 

[Carmel2]

Our Comar AIS aerial has to be a certain distance away from any other aerial's. Something you might need to bear in mind.

 

[CreakyDecks]

VHF travels by line of sight, so range is limited by the distance to the horizon, which is proportional to the square root of your antenna height. If your spreaders are only halfway up the mast then your range would reduce to about 0.7 of what it would be with the antenna at the masthead.

 

[AngusMcDoon]

VHF travels by line of sight, so range is limited by the distance to the horizon, which is proportional to the square root of your antenna height. If your spreaders are only halfway up the mast then your range would reduce to about 0.7 of what it would be with the antenna at the masthead.

For AIS that won't matter. There will still be enough range for anything that's of interest or interested in you.

 

[fireball]

Our Comar AIS aerial has to be a certain distance away from any other aerial's. Something you might need to bear in mind.

You can always separate them vertically ... one the right way up the other upside down ...

 

[William_H]

I would always advocate a VHF com antenna on mast top and an AIS/emergency antenna on the stern rail. This way it can be used in a dismasting. Put the stern rail antenna ona pole perhaps a metre above the rail. In my case my main VHF is like that and works well. good luck olewill

 

[Daydream believer]

My ais aerial sits on a pole on the pushpit 7ft above waterline. I can easily pick up ships 10+miles away .
The wife follows me on vessel tracker &.picks me up 25 miles offshore ok
If one puts an aerial on a spreader one has to be aware that it might snag a cruising chute on the drop( if one has one that is)

 

[Norman_E]

My ais aerial sits on a pole on the pushpit 7ft above waterline. I can easily pick up ships 10+miles away .
The wife follows me on vessel tracker &.picks me up 25 miles offshore ok
If one puts an aerial on a spreader one has to be aware that it might snag a cruising chute on the drop( if one has one that is)

Its a good idea to put any aerial that transmits on a pole, so as to get its signal above the height at which you can receive the radiation. I have an active radar reflector on a pole mounted high enough to ensure that no radiation from it reaches captain or crew.

 

[sailorman]

Has anybody any first hand experience of putting either their VHF or AIS transponder aerial on a spreader? Does it suffer from blind spots caused by the mast or is the normal movement of the boat sufficient to make it a negligable effect?

Thanks

Yoda

my ais aerial is on the stern rail, works very well & can doubles as a saftey VHF aerial

 

[jerrytug]

Its a good idea to put any aerial that transmits on a pole, so as to get its signal above the height at which you can receive the radiation. I have an active radar reflector on a pole mounted high enough to ensure that no radiation from it reaches captain or crew.

The radiation isn't nearly powerful to have any effect on you, so why is it 'a good idea'? (Unless you climb the mast of a warship or whatever).
Putting aerials on spreaders sounds like a good idea to me, and much easier to test or change an aerial in that position.