A dipole antenna is one of the simplest and most effective antennas you can build yourself, requiring little more than wire, a coaxial cable, and a few hardware-store parts. The basic design is two equal lengths of wire, each one-quarter wavelength long, connected at a center feed point to a transmission line. The total length equals one-half wavelength of your target frequency. Here’s how to build one from scratch.
Calculate Your Wire Length
The starting point for any dipole is the frequency you want to operate on. The standard formula for total wire length in feet is 468 divided by the frequency in megahertz. For example, if you’re building a dipole for the 2-meter amateur band at 146 MHz, your total length would be about 3.2 feet. For an HF dipole on 7.15 MHz (the 40-meter band), it would be roughly 65.5 feet.
That formula accounts for the fact that radio waves travel slightly slower along a wire than through open air, which shortens the needed length by about 5% compared to a pure physics calculation. Cut each leg to half the total length, so for a 40-meter dipole, each side would be about 32.75 feet. Always cut a few inches longer than calculated. It’s far easier to trim wire than to splice it back on, and you’ll almost certainly need to adjust.
Choose the Right Wire
For most dipoles, 14 AWG or 12 AWG solid copper wire hits the sweet spot between signal performance and physical strength. Thicker wire (lower gauge number) has less electrical resistance, which means less signal loss. Solid wire outperforms stranded wire electrically because current flows on the outer surface of a conductor, and the gaps between individual strands in stranded wire create extra resistance.
That said, solid copper can stretch and break over time under its own weight and wind stress. Copper-clad steel wire solves this problem. It has a steel core for tensile strength with a copper coating that carries the radio signal (since current travels along the surface). This makes it ideal for permanent outdoor installations where the wire spans a long distance. For temporary or portable setups, standard stranded copper works fine and is easier to roll up and transport.
Build the Center Feed Point
The center of the dipole is where the two wire legs connect to your coaxial cable. You can buy a ready-made center insulator, or make one from a piece of Plexiglas, PVC, or any weather-resistant non-conductive material about 4 to 6 inches long. Drill holes at each end for the antenna wires and a hole in the middle for the coax.
Strip back the outer jacket of your coaxial cable by about two inches. Separate the braided shield from the center conductor. Solder the center conductor to one antenna leg and the braid to the other. It doesn’t matter which side gets which. Wrap each solder joint with electrical tape or heat-shrink tubing, then seal the entire assembly with silicone or a weatherproof enclosure. Moisture getting into the coax is the most common cause of antenna failure over time.
Mechanical strain relief at this junction is critical. If the weight of the coax hangs directly from your solder joints, they’ll eventually crack. Loop the coax through or around the center insulator so the physical load transfers to the insulator itself rather than the electrical connections. Some builders zip-tie the coax to the insulator a few inches below the connection point.
Why You Should Use a Balun
A dipole is a balanced antenna: both legs carry equal and opposite currents. Coaxial cable is unbalanced, with current on the center conductor and return current on the inside of the shield. Without a balun (balanced-to-unbalanced transformer), some current will flow on the outside of the coax shield. This common-mode current causes the feedline itself to radiate, which distorts your antenna pattern, can change your SWR reading depending on cable length, and often introduces noise into your receiver or causes radio-frequency interference in nearby electronics.
A 1:1 current balun at the feed point fixes this. It adds impedance to the unwanted common-mode path while passing your signal through untouched. You can buy one, or wind your own by wrapping about 10 turns of your coax through a ferrite toroid core right at the feed point. For a simpler approach, coil 8 to 10 turns of your coax into a loop about 6 inches in diameter right below the feed point. This “choke balun” provides reasonable common-mode suppression and costs nothing extra. A proper current balun on a ferrite core works across a wider frequency range and provides better suppression.
Hang It at the Right Height
Height matters more than most builders expect. A half-wave dipole at a half wavelength above ground sends most of its energy upward at about 30 degrees, which is fine for regional contacts. Raising it to one full wavelength above ground drops the strongest radiation angle to about 15 degrees, dramatically improving long-distance performance. As a general rule for HF frequencies, higher is always better for reaching farther.
Trees, masts, and roof peaks all work as supports. Attach a rope or cord to each end of the dipole (through insulators to keep the rope from affecting the antenna electrically) and hoist the ends up. The classic flat-top configuration stretches the wire horizontally between two supports of equal height. If you only have one tall support point, consider the inverted V variation.
The Inverted V Option
An inverted V uses a single center support with the feed point at the top and both wire legs sloping downward at equal angles. This is the most practical configuration for many builders since you only need one tall mast or tree. It also changes the antenna’s behavior in useful ways: the feed impedance drops from roughly 73 ohms (for a flat-top dipole) to closer to 50 ohms, which is a better match for standard 50-ohm coax. The radiation pattern also becomes more omnidirectional compared to the figure-eight pattern of a horizontal dipole.
Keep the angle between the legs above 110 degrees for best results. Below that angle, the antenna starts to lose efficiency and the radiation pattern degrades. The sloping also has a shortening effect of 3 to 5 percent on the electrical length, so you’ll likely need to trim a bit more wire during tuning. Aim to keep the wire ends at least a few feet off the ground.
Tune for Lowest SWR
Once your dipole is up in its final (or near-final) position, connect an SWR meter between your radio and the coax feedline. Transmit briefly at low power and sweep across your target frequency range to find where the SWR is lowest. That’s the antenna’s current resonant frequency.
If the lowest SWR point is below your target frequency, the antenna is too long. Trim equal amounts from each leg, a half inch to an inch at a time for HF antennas. If the lowest point is above your target, the antenna is too short, which is why you cut long to begin with. After each trim, re-measure. You’re aiming for an SWR of 1.5:1 or lower across your desired frequency range, though anything under 2:1 is usable.
A practical tip: rather than cutting wire permanently during tuning, fold the excess wire back on itself at each end and secure it with a small clamp or tape. Once you’ve found the right length, make the final cut. Also, try to take your SWR measurements with the antenna in its permanent position. Moving the height, angle, or nearby objects will shift the resonant frequency. Even your body standing near the antenna can affect readings, so step back before measuring.
Ground Your Installation for Safety
Any outdoor antenna is a potential lightning path. Ground every metal mast at its base using a heavy conductor (6 AWG copper wire minimum per the National Electrical Code) running to a ground rod driven into the earth. Connect that ground rod to your home’s existing electrical ground system with 6 AWG wire so all grounds are bonded together.
Install a lightning arrestor on the coax where it enters your home, bonded to the same ground system. These devices contain a spark gap or gas discharge tube that shunts a high-voltage surge to ground while passing normal signals through. Route the coax down to ground level at the mast before it runs to the house, and place the arrestor at that point. This keeps the surge path as short as possible. A static bleed resistor (around 100k ohms) across the antenna’s feed point helps drain the lower-level static charge that builds up from wind and nearby storms, reducing the slow voltage buildup that can damage radio equipment even without a direct strike.
Materials Checklist
- Antenna wire: 14 AWG solid copper or copper-clad steel, cut to your calculated length plus a few extra inches per side
- Coaxial cable: RG-8X or RG-213 with PL-259 connectors (50-ohm impedance)
- Center insulator: commercial or homemade from PVC, Plexiglas, or similar material
- End insulators: ceramic or plastic egg-type insulators, one for each end
- 1:1 current balun: commercial unit or homemade choke balun
- Support rope: UV-resistant dacron or nylon cord
- Solder, heat-shrink tubing, and weatherproofing sealant
- Lightning arrestor and ground rod with 6 AWG bonding wire
A well-built dipole, properly tuned and mounted at a reasonable height, is one of the best-performing antennas for its cost. Many experienced operators use dipoles as their primary antennas for years, and the skills you learn building one transfer directly to more complex antenna projects.