The 1:1 balun is generally designed to match 50-ohm coaxial cable to the balanced loads of center-fed half-wave dipoles or Yagi beam antennas.

Feeding the balanced dipole with coaxial cable will upset the balance as one side of the antenna is connected to the shield while the other side is connected to the inner conductor.

This results in reduction in gain, increase in VSWR, and RFI interferences.

Use 1:1 balun to reduce these. When to use and when not to use a 1:1 Balun since feeding a center-fed half-wave dipole with coaxial cable creates a very small imbalance at the feedpoint (because the diameter of the cable is much smaller than the wavelength), a 1:1 balun is generally not needed in the HF and VHF bands.

Experiments have found it to be needed only when the coaxial cable does not come away at right angles from the dipole (or the plane of an inverted V).

A 45 degree angle created a considerable imbalance. With Yagi beam antennas it is a different matter.

Since hairpin matching networks are usually employed, the effective spacing at the feedpoint is greatly increased and a 1:1 balun is required.

Its biggest effect is the retaining of the antenna's beam pattern by preventing radiation from the feedline.

Waterproof and finished

Working at 150ft for several dipoles