Antenna Insulators

Common materials that you can use for insulating hardware when building antennas. Homemade insulators are inexpensive. I encourage you to make them, especially for your dipoles.

High-quality insulators are mandatory for good performance. A half-wave dipole has very high RF voltage at the outer ends. This means that your end insulators must have a high dielectric factor (high breakdown voltage and infinite resistance). I suggest that you use insulators that are made from polyethy- lene rod or tubing (available from industrial plastic vendors). High-impact polystyrene rod or tubing is also good. Plexiglass T™) is also a good insulating material, but it is brittle and shatters easily, especially during cold weather. It is best to avoid this material for long dipoles. You should also avoid nylon insulators, as they may heat and burn when subject- ed to high RF voltage. PVC pipe and tubing is similarly poor in the presence of high RF voltage.

If you purchase commercially made insulators, try to obtain glazed porcelain ones. Another acceptable commercial insulator is made from molded polyethylene. Radio Shack stores. stock this type of end insulator. They are available also from farm stores that sell electric-fence components. Fig 4 shows how to fashion your own insulators from tubing and solid rod.



Fig 4 - Examples of homemade antenna insulators. The unit at A is made from solid plastic rod. Grooves may be cut at the ends, as shown, with a router. This relieves the stress on the antenna wire and helps to keep the wire from shifting position on the insulator. Suggested dimensions are given for developing a strong insulator. Example B shows how to make an insulator from plastic tubing. A rectangular plastic block (C) is also suitable as an insulator. Grooves can be added to the ends of this unit also.





If you are willing to spend additional money when building high quality homemade insulators, please consider the use of Delrin or Teflon rod. These materials are also available from industrial plastics dealers.

For short-term emergency situations you can make your dipole end insulators from 4-inch pieces of 3/4-inch dowel rod. Drill the holes in the wood, then boil the wooden insulators in canning wax for 10 minutes. The wax will impregnate the wood, which will prevent it from absorbing moisture and becoming lossy. Alternatively, you may soak the dowel-rod insulators in exterior polyurethane varnish for 24 hours. Allow them to dry thoroughly before using them.