Carbon tubing for stern mounted VHF/AIS antenna?

[GTom]

I am planning to add a VHF antenna to the radar pole and was wondering if I could use 3/4" carbon tubing to reproduce something like this? (the "hoop" only) Maybe 2 loops/"mini arches", attached to the mounting screws of the radome and joined above it for more rigidity.

[tkeithlu]

But why? Aluminum or stainless steel will do the job, be cheaper, not weigh much more because the hoop won't weigh much in any case, and the radar pole isn't high enough to really start whipping that antenna around.

[GTom]

Originally Posted by tkeithlu

But why? Aluminum or stainless steel will do the job, be cheaper, not weigh much more because the hoop won't weigh much in any case, and the radar pole isn't high enough to really start whipping that antenna around.

Just got a crazy idea, to make it the simplest: what about gluing a nylon antenna base to the top of the radome?

[Jammer]

Originally Posted by GTom

Just got a crazy idea, to make it the simplest: what about gluing a nylon antenna base to the top of the radome?

I believe that was in fact suggested in one of your earlier, related threads.

[tkeithlu]

As long as you are talking about a short (3 dB) wire antenna, it should work. A 6 dB could wrench the top off.

[slug]

Originally Posted by GTom

I am planning to add a VHF antenna to the radar pole and was wondering if I could use 3/4" carbon tubing to reproduce something like this? (the "hoop" only) Maybe 2 loops/"mini arches", attached to the mounting screws of the radome and joined above it for more rigidity.

The pictured arch is goofy ... the tube diameter is too small , cables are outside and exposed

If you are going to build a custom ant platform do it correctly

Typically a Delta wing platform with single large diameter support tube

Carbon can be used but its not needed . Eglass is plenty strong and not subject to corrosion issues

[thinwater]

I'm must have clicked the wrong forum. I though this was about sailboats, not air defense installations.

[GTom]

Originally Posted by tkeithlu

As long as you are talking about a short (3 dB) wire antenna, it should work. A 6 dB could wrench the top off.

3dB is sure as I have sails and one hull. Not completely abandoned the idea of a heavier, 5' glomex or something similar though.

Originally Posted by slug

The pictured arch is goofy ... the tube diameter is too small , cables are outside and exposed
If you are going to build a custom ant platform do it correctly
Typically a Delta wing platform with single large diameter support tube
Carbon can be used but its not needed . Eglass is plenty strong and not subject to corrosion issues

One thing is sure, Only one antenna will live there not 6... The jury is out for material: stainless, aluminum or some kind of plastic. I also wonder if a metal tube so close interferes with the radar lobe?

[Jammer]

Originally Posted by GTom

I also wonder if a metal tube so close interferes with the radar lobe?

Probably not much. Wavelength is about 3cm for marine radar but the nearfield extends out quite a ways because of the gain. People mount radars on masts all the time and it doesn't seem to do anything but create an area with weak coverage directly aft, and masts are relatively large.


I think the mast is the best place for the radar antenna. Windage, appearance, cost.


Secondary VHF then goes on spreaders, taffrail, backstay, bimini, davits, or mizzen

[slug]

Originally Posted by Jammer

Probably not much. Wavelength is about 3cm for marine radar but the nearfield extends out quite a ways because of the gain. People mount radars on masts all the time and it doesn't seem to do anything but create an area with weak coverage directly aft, and masts are relatively large.


I think the mast is the best place for the radar antenna. Windage, appearance, cost.


Secondary VHF then goes on spreaders, taffrail, backstay, bimini, davits, or mizzen

Yah

Radar on the mast is the only way to go, much less wave reflection , better field of view

Why spend good money on equipment then mount it incorrectly and degrade its performance

[GTom]

Originally Posted by slug

Yah

Radar on the mast is the only way to go, much less wave reflection , better field of view

Why spend good money on equipment then mount it incorrectly and degrade its performance

It came with the boat, moving the radar to the mast would cost me $$$+time. so far no complaints regarding performance.

[Reefmagnet]

I used thin wall 1/2" 316 tubing. Bent it into shape with a plumbers hand bender and mounted it on to the radar pole with a bracket that allows it to be released and rotated down for maintenance. It's only holding a 3dB antenna and anchor light but it's very light weight and doesn't shake about and has to date survived a sideways hit from a waterspout with peak gust over 75 knots.

[barnakiel]

Carbon tubing would be laminated to shape on a male form. Then wrapped and vacum bagged and then cured in an oven. Simple, light, etc. just pain in the A to produce one.


b.