Most whip or vertical antennas used are just one piece of metal or wire run straight up. The center of the coax is connected to that and the shield grounded to whatever is available. What this does is make the ground a rather variable parameter.
Here's a fast and simple variant. Take a length of PVC plumbing tubing and wrap wire on it. Make two identical wire lengths and wind from the center to each end. Then a simple balun set in the middle can be used for the coax connection. The one built as a test used two pieces of #14 stranded wire about 33' (10m) long and a length of PVC drain pipe. A 50/450 ohm balun was used simply because it was handy. This particular one took about ten minutes to make. Two identical pieces of wire, the PVC pipe, and some duct tape.
Set in a corner of a room, it showed good output and slightly less noise pickup than a common whip with the shield side grounded.
It's really nothing more than a vertical dipole antenna. It can be considered to be a loaded dipole because of the coil wound on the PVC tubing.
|Last update: 28 November 2008|