A monoband dipole is an easy and simple monoband antenna commonly used on the HF or shortwave radio bands. To construct a dipole you will need three insulators and some wire. The length of wire you will need depends on which frequencies you desire to operate on. When determining how long to make each leg of a dipole antenna, dividing the frequency in MHz by 468 will give the half wave length in feet. To find the quater wave length, divide that number by two. This will give you the length for each antenna leg.
sources: radioqth.net arrl.org