Radial Wire

Radial wires are an essential component of certain ham radio antennas, especially vertical antennas. They serve as a counterpoise, improving the efficiency of the antenna by providing a better ground plane. Here's an overview of radial wires for ham radio:

Purpose

• Radial wires improve the antenna's efficiency by reducing ground losses.
• They act as an artificial ground plane for vertical antennas.

Types of Radials

1. Ground-Mounted Radials:

   • Wires are laid directly on or slightly buried in the ground.
   • The more radials you use, the better the performance (typically 16–120 radials).
   • Length is generally 1/4 wavelength of the operating frequency but can be shorter if needed.

2. Elevated Radials:

   • Used when the antenna is mounted above ground.
   • Usually requires fewer radials (2–4 is common).
   • Length is critical: exactly 1/4 wavelength of the operating frequency.

Length of Radials

• The length is determined by the formula:
  Length (in feet) = 234 / Frequency (in MHz)
  Example: For 7.1 MHz (40 meters), the radial length is about 33 feet.

• Compromise Lengths: If space is limited, shorter radials will still work but with reduced efficiency.

Materials

• Commonly used materials include:

  • Copper (bare or insulated)
  • Aluminum (less common due to corrosion issues)

• Wire gauge: 14–18 AWG is typical.

Installation Tips

1. Ground-Mounted:

   • Spread the wires evenly around the base of the antenna.
   • If possible, bury the radials 1–2 inches below the ground to protect them from damage.

2. Elevated:

   • Suspend the radials horizontally, ensuring they do not sag significantly.
   • Radials should be insulated from the ground.

How Many Radials Are Needed?

• Ground-mounted antennas benefit from as many radials as possible. Efficiency increases significantly up to about 120 radials.
• Elevated antennas work well with just a few properly tuned radials.