Thermoforming Kydex 100 for Radomes (Antenna Covers)

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Introduction

Radomes protect the enclosed antenna from the environment. It also functions to protect the antenna during shipment, handling and installation. Therefore the radome must satisfy both structural requirements and yet be electrically transparent in the antenna’s operating frequency band. The following properties make Kydex sheet ideal for use as Radome material. The grades recommended are Kydex 100 and Kydex 510. Kydex 100 is a much more readily available material with low order minimums and relatively low cost. Kydex 100 is also stocked in many colors and thicknesses to suit a variety of projects.

Transparency to RF

The the frequencies in question the structural covering must be as invisible as possible to the radio signal. For this to be true the dielectric constant (K) must be low, typically below 3.1 - 3.5 (Air = 1, Water = 80,) and less importantly, the dissipation factor (DF) must be as close to 0 as possible.

See the chart below for full RF transparency.

Low Water Absorption

As opposed to hygroscopic materials such as ABS and fiberglass, Kydex sheet is very hydrophobic (very low water absorption.) This is important because the absorption of water can degrade the antenna’s performance by reducing the transparency to RF.

Long Term UV Resistance

One purpose of the radome is to make it blend in with its environment; to make it less unsightly. Therefore various colors must be available and it must not deteriorate under exposure to the sun. Kydex 100 in white and other light colors have very good UV resistance with minimal color shift over time when used outdoors. Clearjet UV coating may also be used to increase the UV resistance of Kydex 100 without reducing the RF transparency. Please see TB 142 UV Spray for more information.

High impact Resistance

During installation and use, the cover can take a lot of abuse during handling. The cover must be of a high strength material to withstand this abuse. Kydex sheet has one of the highest impact strengths of any polymeric sheet in the industry and is incredibly tough and resilient. This means that it can withstand impacts that would break or shatter most other plastics.

Good thermoformability

The material must be able to be shaped into the desired three-dimensional shape quickly and easily. Kydex sheet is extremely easy to thermoform and will form to the deepest draws and with high definition.Special tooling for forming techniques is not necessary for even the most demanding shapes and detail. RapidMade is extremely experienced working with Kydex.

Flammability Resistance

Kydex 100 and Kydex 510 meet UL Standard 94 V0 flammability resistance. This can be important in meeting local codes for fire regulations. The radome is an important part of the antenna design. It is crucial that the material chosen meet the attributes described above to result in a radome that meets the needs of the designer and functions well over its life span.

See below for full PDF Technical brief on Kydex for Radomes (Antenna Covers)