Ice Radio Products

DC Grounded Antennas – The Myth, The Legend, The Reality

In the lightning protection industry, we often encounter antenna users who suffer severe equipment damage despite using DC grounded antennas. For years, manufacturers have promoted these antennas as offering superior lightning protection, but in reality, this design is one of the most dangerous from a lightning perspective.

Why DC Grounded Antennas Fail at Lightning Protection

Lightning seeks the shortest and least resistive path to ground. Metallic antennas and towers naturally attract strikes by shortening the distance between the sky and earth. When lightning hits an antenna, the energy splits across all available paths. In a DC grounded antenna, part of the surge flows down the coax shield, but the rest travels down the center conductor – directly into your radio equipment.

A lightning strike can introduce 50,000 volts or more to your equipment in an instant, often resulting in irreparable damage.

The Myth vs. Reality

  • The Myth – DC grounded antennas provide superior lightning protection.
  • The Legend – Manufacturers have claimed this for decades.
  • The Reality – Lightning flows through both the shield and center conductor, damaging your gear.

How to Identify and Protect Your System

  • Testing for DC Grounding

    • Disconnect the coax at the equipment end.
    • Use a VOM (Volt-Ohm Meter) on the R x 1 scale.
    • Measure across the center and outer conductors.
    • If you see low resistance (a few ohms), your antenna is DC grounded.

  • Protection Options

    • Option 1: Disconnect the antenna during storms – but this requires you to be present and vigilant.
    • Option 2: Install a blocking-type lightning arrestor at ground level. This device shunts surges to ground while blocking voltage from reaching the equipment. Ensure the arrestor is well-grounded.

Selecting Better Antennas

When shopping for antennas, choose designs that incorporate:

  • Capacitor Feed Systems – Such as gamma matches, which isolate the center conductor and direct lightning into the shield.
  • Link Feed Designs – These designs provide additional isolation, minimizing lightning damage risks.

By understanding the limitations of DC grounded antennas and implementing better protection strategies, you can safeguard your equipment and reduce the risk of catastrophic lightning damage.