VHF Baluns
Baluns and Dipoles
However, technically it is best to use a balun with your half-wave monoband dipole when using coaxial cable as the feedline. A balun is used to connect a balanced antenna ( the half-wave dipole) to an un-balanced feedline ( the coax).
Current Baluns Explained (Choke Baluns)
There are different types of baluns; One to One (1:1), Four to One (4:1), Voltage Baluns, Current Baluns; a One to One (1:1) Current Balun is the balun of choice for a single band dipole application. Current in an antenna is what radiates and the current type balun will force equal current into each leg of the dipole antenna. Balanced current distribution along the halves of the antenna means best radiation pattern shape and antenna efficiency. Current-type baluns provide the desired interface between unbalanced coax and balanced antennas.
The balun also helps prevent current flowing on the outside of the coax. Otherwise, when this current (called common-mode current) appears on the outside of the shield, the feedline behaves as if it were an antenna.
Further Antenna Information for the Amateur Radio Operator
Additional in depth and related information can be found in a number of interesting sources on how to build a balun, constructing a HF Dipole antenna, as well as, multi-band dipole antennas. Antenna handbooks, articles, and other resources are readily available.
