Connect coax cable to vhf aerial?

Question

How do I connect the coax cable to my vhf antennae.

The coax has the solid copper core and the wires in the outer part of the sheath.

Which ones go where??

Answer 1

Generally to connect to a VHF aerial you would use a balun. Balun is a derivative of balanced-unbalanced. It is a little transformer or similar impedance matching circuit and adapts balanced connections to unbalanced, or vice-versa.

Coax is unbalanced, that is it has a single conductor that carries the signal. The shield is there to keep that signal inside and keep interference out. It is constructed in such a way to provide a fixed impedance. For TV reception this is typically 75ohms.

The aerial however is a balanced device. It has two identical halves, and a connection is made to each. It's impedance is typically 300ohms. You could use a balanced feed, twin-lead antenna wire but you'd have to convert back at the set.

So you use a balun. Put an appropriate connector on the coax, an 'F' connector. Then, connect the coax into the balun which has two wire leads for the aerial. Any decent electronics retailer can help you.

You could connect the coax directly, but you will have a mismatch and the shield becomes less effective because it becomes a conductor as well.

Good weather-proof connectors will provide significantly better results. Be sure the balun is designed for outdoors.