Amateur radio antennas for the 80-meter band are finicky because their resonant frequency range is quite narrow when compared with higher frequency (shorter wavelength) antennas. Since most 80-meter radio action occurs near 3.5 MHz, a wire vertical antenna designed for a center frequency of 3.55 MHz is ideal and easy to construct. Subsequent modifications will improve antenna performance in other frequency ranges, including the 75-meter radiotelephone portion of the band. Build a quarter wavelength wire vertical antenna for 80 meters to get on the air fast and inexpensively. Resonance on 40 meters is a bonus.
- 70 feet of No. 12 stranded copper wire
- 2 ceramic or plastic insulators
- 6 foot length of 3/4 inch copper water pipe
- 3/4 inch copper pipe "T" (tee)
- 2 short (1-foot) rubber bungees
- 450 feet of cheap thin steel wire
- RG8 or similar coaxial cable (coax)
- 4:1 current balun with coax connector
- 150 feet of nylon rope
- Tree at least 70 feet high
- Plastic zip ties
- Fishing pole, line and sinker
- Drill with 1/8 inch bit
- Propane torch and solder
- Wire cutters
- Scrap wood block
- Antenna analyzer or SWR meter
Use wire cutters to snip off two 1-foot lengths of wire from the 70-foot length of No. 12 stranded copper wire and set these aside for later. Attach ceramic or plastic insulators to the ends of the remaining 68 feet of wire with 1 foot of overlap at each end such that the total wire length between the insulators is 66 feet.
Use a fishing pole, line and sinker to cast a line high into the upper branches of a tree at least 70 feet high. Recover and remove the sinker and tie one end of a 150-foot nylon rope to the fishing line. Pull the rope up into the tree and and back down so that both ends of the rope are accessible from the ground.
Tie one end of the rope to a 1-foot rubber bungee and slip the other end of the bungee into one of the insulators. Pull the antenna wire, bungee and insulator with the rope until the lower insulator is about 1.5 feet above the ground. Tie the rope securely to the tree. Use this rope to raise, lower and tighten the antenna and to make future modifications or repairs.
Use the propane torch to solder the 3/4-inch copper pipe tee to the 6-foot length of 3/4-inch copper pipe. Drill three 1/8-inch holes through the copper pipe just below the tee. Drill several more holes into the tee, one at each side of the tee and one in the center. Use the hammer and scrap wood block to pound the copper pipe into the ground directly below the suspended antenna assembly. Leave several inches of pipe above the ground to access the drilled holes.
Use a propane torch to solder the two 1-foot pieces of copper wire previously set aside. Solder one piece to the suspended antenna section just above the lower insulator. Solder the other piece to the drilled hole in the center of the copper tee. Use the second rubber bungee to attach the suspended antenna to the copper tee.
Attach the remaining two copper wire ends to the terminals on a 4:1 current balun. Use zip ties to secure the balun to the bungee or to the copper pipe. Attach the coaxial cable transmission line to the balun and run the other end of the coax to your radio operating position.
Cut the 450-foot steel wire into three 150-foot pieces or six 75-foot pieces. Insert these through the 1/8-inch holes in the copper pipe and lay them out in 75-foot lengths in a radial pattern away from the antenna and as evenly spaced as possible. This six-radial system will act as a ground plane to improve the efficiency of your antenna.
Solder all wire-to-wire and wire-to-pipe connections securely for both strength and conductivity. Check the resonant frequency range of your new antenna with the antenna analyzer. You should find low standing wave ratio (SWR) between 3.5 and 3.6 MHz of the 80-meter amateur radio band. As a bonus, you should find resonance on the lower end of the 40-meter band as well.
- Chem Hawaii: 80/75 Meter Wire Antennas
- Seed Solutions: G. Ordy, W8WWW: Hex Array - 80/40 Meter Vertical
- MCARS: 80 Meter Vertical 1/4 Wave Antenna
- Money Smith: W4NFR; QUARTER WAVE 80 METER VERTICAL ANTENNA
- A. Christman, K3LC; 2004; NCJ-ARRL, March-April 2004
- Ham Universe: The KJ4IIF 75 METER 1/4 WAVE COW PASTURE VERTICAL
- Photo Credit George Doyle/Stockbyte/Getty Images