Non-conductive guy cables use

[RadioFan2J3]

I am very aware of the use of non-conductive guy cables where the guy cables pass through the near field of FM and TV band transmitting antennas, but of all of the medium wave antenna systems in the United States, do any of these guy cable systems use 100% non-conductive guy cables?

 

[Kelly A]

I am very aware of the use of non-conductive guy cables where the guy cables pass through the near field of FM and TV band transmitting antennas, but of all of the medium wave antenna systems in the United States, do any of these guy cable systems use 100% non-conductive guy cables?

Sure, some physically shorter towers tuned to the high end of the band. Non conductive cables made of nylon and Kevlar are commonly known from a company called Phillystran: https://www.phillystran.com/
The upside of using these cables as guy wires are they don't require glass insulators in the guy wires runs to keep the tower from electrical ground. The downside is they need replacement much more frequently from being exposed to the weather. UV rays over time will cause the materials to break down and lose tensile strength. If you accounted for the cost of replacing Phillystran guy wires every six to ten years, including having to hire a tower crew to re-tension and replace the guys, one is better off staying with good ol steel cables and glass insulators.

 

[RadioFan2J3]

Kelly, thanks. Is the replacement cycle that short? Six to ten years?

We have Phillystran at one MW site and right now, about 90-95% of the guy length is Phillystran with the exception of the steel tail at the ground guy anchor point per Phillystran's recommendations.

I was just curious about how many MW stations actually have essentially 100% Phillystran in their guy cable system. I guess I'd never noticed it in any MW sites in the US - mostly the use of Phillystran was around the FM or TV antennas on a tower, particularly side mounted antenna systems.

 

[Kelly A]

Kelly, thanks. Is the replacement cycle that short? Six to ten years?

It depends on several factors. If a station is in Death Valley baked in the sun most days, replacement could be that short. In areas with big seasons, like Wyoming or mountainous parts of Arizona, you would likely have to re-tension them at least every four or five years. Depending on the guy length and number of times being re-tensioned, it's easy to determine whether the guy is getting close to needing replacement.

I was just curious about how many MW stations actually have essentially 100% Phillystran in their guy cable system. I guess I'd never noticed it in any MW sites in the US - mostly the use of Phillystran was around the FM or TV antennas on a tower, particularly side mounted antenna systems.

Couldn't give you numbers. As you pointed out, it's common to run a section of Phillystran in front of a side mounted FM or TV antenna to reduce re-radiation.

 

[bigdonho]

Here in south Florida the UV rays just eat the stuff up. Even the fiberglass rods we use on tower skirts don't last much more than 5 years.

 

[RadioFan2J3]

Here in south Florida the UV rays just eat the stuff up. Even the fiberglass rods we use on tower skirts don't last much more than 5 years.

Thanks. I looked at some photos taken of the Phillystran and it appears there is a black plastic outer cover which shields the strands from direct UV. I can't determine the specific year these guy cables were last replaced, but I am almost certain it has been well past 5 years ago.

 

[Kelly A]

Thanks. I looked at some photos taken of the Phillystran and it appears there is a black plastic outer cover which shields the strands from direct UV.

That's actually an extruded polyurethane jacket that protects the HPTG (Kevlar) center. That said, even polyurethane cracks and fails over time and exposure to UV and seasonal elements.