Ground radials are wires that are attached to the base of a Ham radio tower radial plate, and radiate around the base to improve the efficiency of the transmitter. If no ground system is in place, signal energy is converted into heat -- instead of radiated as radio waves. This reduces the efficiency of the transmitter. While broadcast antenna systems use the optimal 120 ground radials, most Ham radio antennas can use 16 ground radials with an acceptable loss of efficiency.
Things You'll Need
- Radial ground plate kit for 16 radials
- Adjustable wrench
- Measuring tape
- No 14 insulated copper wire
- 1/4-inch ring terminals
- Electrical pliers
Place the ground plate at the base of the antenna. Tighten the U-bolt saddle clamp nuts finger-tight, and then finish tightening them using an adjustable wrench. The saddle clamp should be tight enough to prevent movement of the ground plate, and provide a tight connection to the metal pole.
Measure 65 feet of wire per ground radial. The length of the ground radial is a function of the wavelength of your transmitter. For a 60 meter frequency, the ground radial needs to be 1/4 the frequency length, or 65 feet long. Strip off and insert the end of the wire into a 1/4-inch ring terminal. Using the electrical pliers, clamp the end firmly in place, creating a tight electrical bond.
Loosen the 1/4-inch nut from the ground plate bolt and place the ring terminal over the bolt. Tighten the ground plate bolt finger-tight by turning the nut clockwise. Tighten the nut with an adjustable wrench to create a tight electrical bond.
Stretch the wire horizontally to create a perpendicular line to the tower. Next to the wire, break the top of the dirt and bury the wire about an inch under the soil. While the wire could lay on the surface, burying the wires will help prevent the system from being disturbed by people, mowers or animals.
Tips & Warnings
- The antenna efficiency will continue to improve until about 32 ground radials are installed. At that point, transmitter efficiency will improve marginally. If you will be using more than one frequency, create different lengths of radials based on the frequency used and divide by four. Ground radials do not have to be longer than the antenna is tall -- the additional length will not significantly improve performance. (Ref 1 p3-6)
- The ground radials are not the grounding system for lightning. The tower should have an effective lightning grounding system and lightning arrestors installed, in addition to the ground radials.
- "The ARRL Antenna Book, 20th Edition"; R. Dean Straw; 2007
- Bencher: Ground/Radial Systems
- Photo Credit antenna on island image by Alexander Maksimov from Fotolia.com
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