While dipoles are very efficient antennas, they are not the only way to go. If you only have one support an end-fed antenna may suit you better. However, they can be a cheap and easy way to get a multi-band antenna up for the HF bands, but you must usually use an Antenna Tuning Unit ATU or other matching device. You must also have a good earth connection — not just the mains earth that the rig or power supply uses. You can also add perhaps four or more wire radials at least a quarter wave long at the lowest frequency of operation, running out from the earth stake along the ground in different directions. These can be buried — the exact length of the radials is not critical, but more, shorter radials are better than fewer, longer ones. Traditionally, many books may suggest that your end-fed wire should be a quarter wave long at the desired operating frequency.
Wire antennas for amateur radio at DX Engineering
End-fed wire antennas
Figure 1 is a treasure map. Contained within this diagram is one of Mother Nature's important secrets. The mystery of wonderfully loud signals emanating from insignificant looking antennas strung between two cooperative trees is explained in this simple chart. The all time favorite wire antenna is the half-wavelength, center-fed, dipole.
For small portable dipoles without balun. The model for coaxial cable has a PL jack. The version for symmetrical feeding has a proper strain relief for the wire feed line.