Why $250 insulator?

[hellosailor]

Broadcast stations rarely have to take the shock load of falling off a 20' wave in storm force winds. Probably similar to expecting equipment to hold up when a 8.8 earthquake hits town.

I suspect that porcelain tends to shatter from repeated shock loads, as opposed to a more gradual sustained load, as well.

Hard numbers would mean way more than "Well it looks like it might do the job". There'd have to be a lot of rich dumb sailors out there, if they were using $250 parts instead of $15 parts, just for the hell of it.

[Viking Sailor]

Originally Posted by TreblePlink

It's certainly possible to do that, but depending upon how well all conductors are additionally bonded, the insulated backstay has a greater potential for impedance stability under windy and wet conditions.

Many AM broadcast stations use a grounded tower antenna with a wire skirt feed system - known as a folded unipole. I've tuned and troubleshot many of them. The conventional approach is to insulate the entire tower on a large porcelain insulator and feed it at the top of the insulator.

They both perform about the same, but the folded unipole allows easier additions of (money-making) antennas on the tower. The downside of the unipole is that bonding of all attached conductors is critical for stability, and is the most common cause of failure.

The stability of the antenna connections does not seem to be a problem. This is probably do to the backstay being under a significant amount of tension. There has never been any indication that there is instability in the grounded backstay antenna. However, if one was concerned about this problem, it is possible to rig a SS jumper cable to bypass the potentially unstable connections.

[TreblePlink]

Originally Posted by Cheechako

You used to see them on boats all the time. So I guess they work! My gut always told me they would be fragile for some reason, but they are used on utility poles a lot. I guess the material is in compression from the wire not tension, That may be why they work well. What are the fancy marine ones made of anyway? Some type of plastic?

'Nuff said.


I suspect the main reasons they've fallen out of favor is a. They have (slightly) more weight & windload. b. They need flexible 7 x 19 cable to do the wrap-through, and 1 x 19 is now favored for standing rigging.

On my 28 foot boat that uses all 1/4" cable, I think the porcelain will be fine.

[BlackHeron]

FYI: WestMarine is clearing out their swaged Ronstan backstay insulators at a significant discount if anyone is looking for one. All they have left are the 7/32", but they are only going for $17.44 at the moment. Only 3 are left in stock so don't wait around if you think you might want one. I picked one up myself to have for the next time I need to replace the standing rigging. It was last done in '12. We don't run a bottom insulator, so I only need one. Just DO NOT touch the backstay when someone is transmitting on the HF on SV Barry Duckworth o.O

https://www.westmarine.com/buy/ronst...9?pCode=283566

[Viking Sailor]

Originally Posted by Posse

Viking Sailor, would you mind putting up a diagram of that antenna design?

OK, the antenna is pretty simple to implement as there are no need to cut the backstay .etc. Sorry I don't have any drawing tools on this computer.

[roverhi]

Used ceramic insulators on our Westsail 32 backstay with 1x19 wire and nico press swages. Sailed to French Polynesia, back go Hawaii and more than 10 years sailing around Hawaii without a problem.