Antennas and feed lines

An antenna couples a radio signal to the space around it. Its behaviour depends on frequency, geometry, installation height and nearby objects. A feed line carries energy between the radio and antenna.

• Dipole: a balanced antenna with two conducting sections, often used as a practical starting point for HF.
• Vertical: useful where space and installation constraints favour a vertical structure; the return-current path is part of the design.
• Directional antenna: concentrates radiation in selected directions. A Yagi is a familiar example.
• Loop: a closed conducting path, with many possible sizes and designs.

No antenna is best for every station. Available space, bands, mounting options and the intended paths help determine a suitable design.

Coaxial cable is widely used because its shielding and routing are convenient. Balanced lines are another option. Loss, impedance, weather protection and connector quality all affect the complete system.

Standing wave ratio (SWR) describes mismatch along a transmission line. A low SWR is useful, but it does not by itself prove that an antenna radiates efficiently. A dummy load can present a good match while intentionally converting most transmitted energy to heat.

Include a diagram, dimensions, feed-line type and length, installation height, measurement method and operating conditions. Keep measured results separate from predictions and simulations.

See the article template for a consistent way to document a design.