antenna conduit

[jpolenek]

I've noticed that everyone buries ther antenna coaxial cable directly into the foam and glasses over it. Is there any chance of the cable needing to be replaced within the life of the plane? If so, why not install nylon tubing, and run the cable inside that?

 

Joe Polenek

[rickh]

'Spose you could, but how would you attach the coax to the antenna foil?

 

*I'm* more worried about a bend/break/snap where the coax pops through into the fuse... on my tub anyway. Maybe I should add a dollop of silicone as a strain relief?

[jpolenek]

'Spose you could, but how would you attach the coax to the antenna foil?

 

You'd still need to cut through the skin to do the hook-up, but the nylon conduit would allow you to remove the old cable and feed in a new one very easily.

 

The question is: what's the likelyhood of coaxial cable (or its connection points) ever failing and needing repair or replacement?

 

 

Joe Polenek

[argoldman]

You'd still need to cut through the skin to do the hook-up, but the nylon conduit would allow you to remove the old cable and feed in a new one very easily.

 

The question is: what's the likelyhood of coaxial cable (or its connection points) ever failing and needing repair or replacement?

 

 

Joe Polenek

Especially when it is potted as it is in epoxy/micro

[Big Steve]

That is the reason that a lot of builders install two of each antenna so they will have a back up incase of a failure. Build on STeve

[Cozy1200]

That is the reason that a lot of builders install two of each antenna so they will have a back up incase of a failure. Build on STeve

Dual Nav/Coms!!

[raiki]

In my experience in electronics and so forth (mostly in heavy industry), if anything breaks it will be at the end of the coax, or where there are sharp bends, panel piercings (cable being cut) or streched places. Thats why sharp bends are not recommended in all the texts on the issue.

 

Because the connection to the copper foils, and the foils themselves, are effectively potted the probability of them snapping is very low.

 

The issue I would have with coax in a nylon conduit is that the vibration would cause the coax and/or the tubing the wear through where they contact, exposing the shield which could then wear though. Admittedly this would take a long time. The shield rubbing on some form of plastic I am pretty sure would make some electrical noise. Conduits are not suited to high vibration areas.

 

In my opinion, adding conduits would be more likely to cause failure. In the end follow the plans and the RST document and all will be good. I haven't heared many reports of the plans system ever failure so that brings me to an old quote we should all be using. "If it aint broken, don't fix it."

 

I agree with Rickh, the entry into the fuse and strain relief are important considerations (and the potting of the connection/coax/torroids is strain relief at the foil end).

[jpolenek]

The issue I would have with coax in a nylon conduit is that the vibration would cause the coax and/or the tubing the wear through where they contact, exposing the shield which could then wear though.

In the end follow the plans and the RST document and all will be good.

In the documentation that comes with the RST antenna kit, Weir says that it's ok to run the coax in the same [1" diameter] channel that runs through the wing for the lighting wires. Is everybody doing that or are builders opting to mill a channel into the surface, and laying the coax closer to the skin? Running it through the existing hole is easier but allows the cable to move around and rub from the vibration. On the other hand, running the coax close to the skin puts it further from the neutral axis in bending and could subject it to compression/tension when the wing flexes, especially if it's microed in place.

 

Which method is better?

 

What about soda straw conduit instead of nylon? Weir mentions soda straws in the gear legs.

 

Joe Polenek