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EMI/RFI Shielded Waveguide Air Vents

RFwaveguides

ETS-Lindgren's Waveguide Air Vents are manufactured to meet a variety of customer requirements.

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ETS-Lindgren's Waveguide Air Vents are manufactured to meet a variety of customer requirements. The electric field, planewave, and microwave shielding effectiveness of the brass or steel honeycomb is virtually identical because of the consistency of the solder fusion process. Steel provides higher low-end magnetic field shielding effectiveness. However, brass can satisfy non-ferrous requirements and is favored in areas of high humidity.

Key Features
  • Available in 3.175 mm (1/8 in) and 4.76 mm (3/16 in) Honeycomb Cell Geometry
  • Adaptable to a Variety of Mounting Flanges and Gasket Techniques
  • Brass or Steel Core Material with Tin Coating for Superior RF Performance and Corrosion Resistance
  • Minimal Air Flow Resistance and Pressure Drop
  • Continuous Solder-fused for Superior Strength and RF Performance
Product Details
Product Features

Typical Mounting Methods

Since the vent-to-shield seal is normally the limiting factor in shielding performance, the following waveguide-to-shield seals are recommended.

Soldering and Brazing

Whenever possible, enclosure walls should be fabricated in a horizontal position to allow soldering or brazing in a lightweight (26 gauge copper or galvanized steel) frame to the shield wall. This produces excellent RF seals that provide reliable performance for long periods of time.

Welding

If the shielding material in the walls and ceilings is heavy enough to weld, vents with an angle iron frame should be specified. Since the waveguides are soldered into the frames using 60/40 solder, care should be taken to keep the honeycomb-to-frame joint under 150o Celsius. The preferred installation method is to use a skip welding technique around the frame until the weld line is completely closed.

Gasket Seals

Where soldering and welding are not practical, RF gasket seals can be used. Monel or tin coated gaskets provide the best RF seal. The mounting surface can be tin-lead plated or plasma spray tinned. A light cleaning of contact surfaces before assembly will insure maximum seal performance by removing unwanted metal oxides before the seal is formed.

Contact surfaces of mating surfaces should be rigid enough to carry pressure along the gasket for maximum shielding performance. Maximum enclosure-to-vent shield performance can be achieved by observing the precautions of compatible metals and by spacing the fasteners at no more than 10.16 cm (4 in) on center.

Whenever metal ducts are connected to the waveguide air vents on a shielded wall, a dielectric spacing collar is needed to create a non-conducting break on the duct. The purpose of this break is to keep RF currents on the surface of metal ducts from transferring to the shield wall and lowering shielding effectiveness. The dielectric break may take the form of a rubber or canvas boot, a wooden spacing collar, or other dielectric medium.

Minimum Resistance to Air Flow

The honeycomb (or hex-tube) design combines the highest shielding performance with the lowest resistance to air flow. Cell geometry allows the maximum amount of open space while uniformity and depth of the honeycomb tubes reduces air turbulence.