Calculator: Half-Wave Dipole

The half-wave dipole is the most fundamental and reliable antenna. It is the standard against which many other antennas are compared (their gain is measured in dBd).

In emergency situations, a wire dipole hung between two trees (Inverted V) or stretched horizontally can provide clear shortwave (HF) communications over thousands of kilometers, or a solid local VHF base station.

How it works

• It consists of two wire legs or arms of equal length.
• The coaxial cable connects in the center: the center conductor (live) to one leg and the shield (ground) to the other.
• Ideally, it should be placed at a minimum height of half a wavelength above the ground.

Tactical Calculator (142.5 / f)

Enter the operating frequency to get the cutting measurements. (This calculator uses the factor 142.5 instead of the theoretical 150 to compensate for end effects in common wire).

Center Frequency (MHz)

CALCULATE

Cutting Results

Total Length (L) -- meters

Each Leg (L/2) -- meters

⛺ Emergency Deployment Guide (For Non-Techs)

• Setup (Inverted-V vs Horizontal): The easiest way in the field is to use a single tree or central mast (“Inverted-V” setup). You tie the center (where the coaxial cable is) as high as possible and pull the two ends down at an angle of about 45 to 60 degrees. If you have two trees at the same height, you can stretch it Horizontally. Both work excellently.
• Recommended Height: Higher is better! Try to get the center of the antenna at least 15 to 30 feet (5-10 meters) off the ground.
• Isolators: The tips of the antenna wires must not touch metal or the ground directly. Use nylon rope (paracord), plastic, or even large clothing buttons as insulators between the antenna wire and the tying rope.
• Feed Line (Coaxial): Radios transmit best with 50-ohm cable (like RG-58). However, in an extreme emergency, if you only have TV cable (75-ohm RG-6), USE IT! If you cut the antenna measurements correctly, the SWR (Standing Wave Ratio) will stay within safe limits.