My project in 2025 is going to be adding vibration dampening on all my long wire antennas. This project will take stress off the insulators, hardware, and support poles especially during icing and windy conditions similar to what's used on high voltage power lines.
Vibration dampers on Antenna lines will reduce the vibration of the wires caused by the wind, thereby reducing the probability antenna hardware damage.
The galloping phenomenon is prone to occur when transmission lines are subjected to wind forces. Long-term vibration leads to metal fatigue damage at the suspension, which leads to serious accidents such as wire breakage and tower collapse.
Galloping has an amplitude measured in meters and a frequency range of 0.08 to 3 Hz
The Spiral Vibration Damper is a motion control product used to dissipate aeolian vibration that may occur on cable spans. Using the recommended number of Spiral Vibration Dampers minimizes bending strain, protecting the cable from long-term fatigue due to aeolian vibration. Aeolian Flutter has an amplitude of millimetres to centimetres and a frequency of 3 to 150 Hz
Aeolian vibration is generally produced by
wind velocities below 15 miles per hour
(MPH). Winds higher than 15 MPH usually
contain a considerable amount of turbulence, ice and snow is also a factor.
When wind blows across overhead antenna or transmission lines, it can cause them to vibrate or oscillate, which can lead to fatigue and even failure of the conductors over time.
Vibration dampers are typically installed along the length of the transmission line at regular intervals. They work by absorbing some of the energy of the oscillations, which reduces the amplitude of the vibrations and the stress on the conductors. This helps to prevent damage to the conductors and hardware.
The phenomenon know as Aeolian (or Second Mode) Vibration is caused by low-velocity, steady winds, normally ranging from 5-35mph and giving rise to frequencies of 2-20hz. This vibration is believed to be predominantly caused by air vortexing around the structure. As this steady stream of air passes across the pole, vortices are formed on the backside of the structure. The vortices alternate from the top and bottom surfaces and create alternating pressures that tend to produce movement at right angles to the direction of the air flow. This vortexing causes a high-frequency, short-cycle harmonic reaction in the structure — creating extreme stresses. This phenomenon is site specific and is, unfortunately, not predictable. Aeolian Vibration can be altered by as little as the shape of the structure, changing the fixture style or location, or having an object such as a tree or building
ABOVE: Is one end of an antenna
Galloping antenna wires can occur when freezing rain creates icicles and odd-shaped ice on transmission towers and conductors. High winds push on the icicles and conductors and lifts them up, creating a galloping, or jumping, motion. If you see galloping transmission lines, stay clear. Do not approach the transmission lines or towers
Below Galloping and Aeolian Vibrations | Transmission Lines
Top of the antenna poles, the wire cable is going through pulleys
Lower on the pole is vibration dampers
ABOVE: A Dog-bone unit or Stockbridge damper
Helical vibration damper consisting of a central weight suspended by two or more steel messenger wires. The weight counterbalances while the brackets provide aerodynamic resistance to the wind-induced vibrations.
THE MATH
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