INVISI-SHIELD® Electrically Transparent Ice-Shield

The ERI INVISI-SHIELD® provides protection for FM antennas without impacting the antenna pattern. This specially designed electrically transparent ice shield can be mounted immediately above the array and at intermediate locations within the array for FM antenna the are 8-bays of more without impacting the FM antenna’s electrical performance.

Radial icing occurs when water droplets are large enough to fall from the atmosphere and freeze on objects near the ground. The frozen deposits form a clear ice shell on antennas and tower components. Radial ice conditions are typically very short in duration. The thaw that follows releases segments of ice which fall or sail causing significant damage to antenna elements mounted below the top of the tower.

The antenna elements are particularly susceptible to falling ice. Radial ice has a unit weight of 56 pounds per cubic foot (897 kg/m³) and can cause significant damage to unprotected tower appurtenances. Steel ice shields can offer some degree of protection. But due to pattern distortion inherent to their construction the steel shields are placed at distances which diminish their ability to adequately protect the FM antennas.

Some applications of a steel ice shield are prohibited due to the detracting effects it could have on neighboring antennas. The ERI INVISI-SHIELD® is an electrically transparent ice shield. Utilizing custom fabricated materials and careful placement of connection components has resulted in a structure which has no perceptible effect on the antenna’s pattern. The INVISI-SHIELD® can be mounted directly over an antenna element. This close proximity allows the INVISI-SHIELD® to be significantly smaller while increasing protection when compared to a steel shield. The smaller size also results in less load to the tower. The electrical transparency of the INVISI-SHIELD® will permit installation between antenna bays in extreme icing conditions. The top edge of the INVISI-SHIELD® is permeated with a silicone grit. This material helps trap potential freezing rain on the shield reducing the potential of radial ice accumulation and detuning of the antenna element.

Specifications

  • Load Rating:
    300 PSF (1465 kg/m²) uniform distribution 7,200 lbs. (3265.8 kg) total capacity, High Impact Resistance
  • Size:
    6 ft x 4 ft | 1.83 m x 1.22 m
  • Weight:
    No Ice 225-lbm | 102.1-kg
  • 1/2-inch (13 mm) Ice 500-lbm | 226.8-kg
  • Effective Project Area (Normal Exposure):
    No Ice 8.8-ft² | 0.82-m²
  • 1/2-inch (13 mm) Ice 10.0-ft² | 0.93-m²
  • Effective Project Area (Transverse Exposure):
    No Ice 8.4-ft² | 0.78-m²
  • 1/2-inch (13 mm) Ice 9.7-ft² | 0.90-m²

Features and Benefits

  • Protection from falling ice
  • No perceptible pattern distortion
  • Can be mounted directly over each element
  • Reduces potential accumulation of radial ice
  • Convenient work platform

INVISI-SHIELD® Product Brochure