1/4 Wave Ground Plane CB Antenna
This CB antenna consists of a driven element and four radial wires that act as a ground. The driven element receives the transmit energy from the rig.
Parts List
1. 104″ (264 cm.) [I 02' (259 cm.)] piece of aluminum pipe or conduit
2. ¾” – 1″ diameter
3. Two U-bolts, same size as pipe
4. One sheet metal screw
5. One J-hook
6. Four “egg” ceramic insulators
7. 408″ (10.22 m.)[400'"(10.2 m.)] of 16 gauge wire
8. Rope, enough to guy the ground radial, depending on the height of the antenna
9. A couple of two-by-fours
10. Electrical tape
11. Silicone sealer to cover coax connection
The inside conductor of the coax is connected to the aluminum pipe by means of a screw into the bottom of the pipe. See the detail drawing on this page. Coat this connection with sealer or cover it with tape to protect it from corrosion.
All vertical antennas need to be grounded in some way. A mobile CB antenna uses the car body as the ground. On this CB Antenna, the four radial wires are used as the ground. This is called the ground plane of the antenna.
The braided wire which forms the outside conductor of the coax is soldered to all four radial wires. The wires must be exactly 264 cm (104′) long [259 cm(102") long] (¼ wavelength).
Remember that the inner conductor and outer braid of the coax must not touch each other, nor can the radials come in contact with the driven element. The radials slope down at about a 45 degree angle in different directions, and are tied to the insulators. Rope or nylon cord is then tied to the insulators and used to hold the radials out. They can be attached to anywhere convenient; trees, a fence, house, etc.
If you are short on room for such a radial system, you can use 104″ (radials) and 102″ (driven elements) pieces of aluminum tubing, or suspend the wires on PVC pipe, bamboo, or 1″ x 2″‘ wooden sticks. It’s a must to check the SWR when done. It should be lower than 2, and ideally lower than 1.5 or 1.3.
A ¼ wave ground plane CB antenna made from wire can be suspended from a tree. We have talked to stations over 40 miles away using this antenna up about 30 feet high, running a mobile rig for a base.
