Hobbies And Interests
Things You'll Need
Instructions
How to Build a 10 Meter Wire Antenna With the Lowest SWR
Decide what frequency is to be your center frequency and apply the formula for a half wave dipole: L (feet) = 468/F (MHz). For example, if you wish to operate between 28.0 MHz and 28.1 MHz, use the center of that range, 28.05 MHz as your center frequency and apply to the formula: L (feet) = 468 / 28.05 = 16.684 feet for the total length of your dipole or 8.342 feet for one side of the antenna.
Secure the two copper wires to each side of an insulator leaving about four inches of wire with about two inches stripped of insulation on each side.
Measure out the exact length of wire your antenna requires on each side from the formula above. It is better to err in excess length, which can be trimmed off later as needed.
Securely attach the two remaining insulators to the remaining ends of the two copper wires so the total distance from end to end is the length you obtained from the formula. Leave the excess wire dangling until you test your antenna and trim it to its final length.
Strip off a few inches of insulation and solder the two conductors of the 300 ohm twin-lead wire to each half of the dipole across the center insulator. Attach the two leads at the other end of the 300 ohm twin-lead to a 4:1 current balun just outside of your operating position. Attach 50 ohm coaxial cable to the current balun and run it inside to your operating position.
Use nylon ropes to raise and lower the center insulator, antenna and twin-lead transmission line to a height of 30 feet or more. Leave excess rope attached for lowering and modifying the antenna later. Attach the two end insulators to ropes and raise or lower them as needed from tree limbs or a pulley on a building or pole mast.
Attach an standing wave ratio meter between your radio and the coaxial lead entering your operating position. Transmit on your operating frequency and check forward and reverse standing wave ratio readings. If the ratio is 1:1 your antenna is resonant and ready to go on the air.
If necessary, make adjustments to your antenna. Shorten each half of the dipole in small equal increments and repeatedly retest the standing wave ratio until a 1:1 match or resonance is achieved on your operating frequency. Experiment to see how wide a range of frequencies you can use with a 1:1 ration and then again with a 1.5:1 or lower ratio. This range in frequency represents the bandwidth of low standing wave ratio for your new antenna.