Working with antennas has long been an exciting hobby both for the novice and the expert. Whether you are building one from a kit or from items laying around the house, you're sure to have a great time and learn in the process. Knowing how to build a multiband scanner antenna for UHF, VHF and higher bands will help a person understand how the antenna works as well as keep up to the minute on the exciting news and events around his city.
How to Build a Multiband Scanner Antenna
Carefully mount the SO-239 connector in the table vise so that the male side of the plug is facing upward. Take one of the rods and using the #80 sandpaper, sand one inch of the rod on one end. This will allow the solder to adhere to the rod and connector, forming a better connection. Apply a small amount (about the size of a pencil lead) of flux around the end of the rod that has been sanded. Insert the sanded end of the rod into the SO-230 connector pin and hold this carefully. Using the solder and soldering gun, solder the rod to the pin until there is a tight and clean bond from the rod to the connector pin. Use just enough solder to make the connection; do not oversolder. Take note to NOT overheat the connector pin with the solder gun and melt the plastic insulator inside the connector.
Take the four remaining rods and make sure they are perfectly straight. Using the needle nose pliers on one end of each of the four rods, make a small bend to to form a circle just large enough for the #6 bolts to go through. Attach the four rods, one to each corner hole on the SO-239 connector using the #6 bolts and nuts. Make sure they are a snug fit with the pliers, but do not overtighten to avoid stripping the threads.
Holding the connector carefully level in the upright position with the one rod straight up, use the pliers and bend the four rods (radials) at the base of the SO-239 connector to approximately 45 degrees. Check each bolt and nut once again to ensure it is still snugly tight. Measure each of the four radials and main upright element to 20 inches and cut off any extra wire. Apply the clear window and door sealant to the top of the connector to help keep rain and moisture out of the connector and cable.
Using a string, hang the antenna from an outdoor eave or inside the attic. Attach the coaxial cable to the SO-239 on one end and the other to the scanner.
This antenna will work on most UHF, VHF, aircraft and police frequencies that the average scanner will operate on. You can also use bicycle spokes or piano wire for your rods (radials). For best reception, hang the antenna outside.
Safety must always come first. Never hang or mount your antenna next to or around any power lines. Wear safety goggles to avoid injury to the eyes from the radials as you assemble your antenna.