Dipole Antenna Coaxial Cable

The use of coaxial cable is far more common in view of its convenience and performance when operating with close by objects or when being routed through walls and around rooms.

Dipole antenna coaxial cable.

If you connect the inner and outer conductor of a coaxial cable to the two arms of a dipole then the dipole will in fact work as an antenna but the outer conductor of the cable will alsoradiate receive. A coaxial cable transmits the audio video signal from your antenna to a tv or a connector box. This is because coax is what is termed an unbalanced feeder i e. Some antennas come with a coaxial cable but if you have a large antenna mounted on your home s roof it might use ribbon cables instead of a coaxial cable.

This webro cable has a velocity factor of 0 81 very good indeed for feeding the antenna but a poor choice for making elements for the antenna itself the reason being you require a inefficient leaky coax element of 0 66 velocity factor to absorb as many signals over as much of the desired band at the antenna then transfer the signal down a very efficient coaxial to the radio. Follow the 11 steps below to attach your antenna to a coaxial cable. Find out about dipole antenna feed impedance calculations determination etc. And how to feed a dipole antenna for optimum efficiency.

When a coaxial cable is connected directly to a dipole antenna however the currents will not neccessarily be equal. How to make an fm antenna using coax and lamp cord that works great if made as shown in the video it certainly worked great for me. In figure 1 a coaxial cable is connected to a dipole antenna. Many types of coaxial cable have a characteristics impedance of 75 ω hence the dipole antenna can be fed with coaxial cable of 75 ω two wire which is a good match for a half wave dipole antenna.

Thisis the problem a balun solves. The outer shield is connected to earth and the antenna is balanced. In the diagram each leg of the dipole antenna is joined to the feeder. For a dipole antenna to operate properly the currents on both arms of the dipole should be equal in magnitude.

This can either be open wire twin feeder or coax can be used. Strictly speaking a balun should be used when coax or coaxial cable is used. If you ignore it you will still have an antenna but possibly not the antenna you intended to design. Coaxial cable is more convenient for use especially at very high frequencies.

The above versions need some sort of matching to enable use at 50 ohms.