Feedlines and beam antennas

How does the signal get from my radio to the antenna?

The feedline

A Feedline is the cable connecting radio equipment to the antenna.

Coaxial cable

Coaxial cable is a centre conductor encased in insulation, surrounded by a conducting shield and covered in a weatherproof jacket. Its usual impedance is $50\ \Omega$ or $75\ \Omega$.

Twin lead

Parallel-conductor feedline (twin lead) is two parallel conductors held a uniform distance apart by insulating material.

For an HF dipole, compared with RG-58 or RG-213 coax:

• $300\ \Omega$ twin lead has higher impedance and lower loss over long runs.
• Its disadvantage, as open-wire feeder, is that it is affected by nearby metal objects.

Beam antennas

A Beam antenna is an antenna whose radiation pattern concentrates more of the signal in one direction than others.

You now know

• A feedline is the cable connecting radio equipment to the antenna.
• Coax has a centre conductor, insulation, a shield and a jacket; usual impedance is 50 or 75 ohms.
• Twin lead is two parallel conductors held apart by insulation; 300 ohm twin lead has lower loss over long runs but is affected by nearby metal.
• A beam antenna concentrates more of the signal in one direction.