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How to Make a Coaxial FM Transmission Antenna

Ham Radio, also know as amateur radio, has long been an exciting hobby for all ages and levels of interests. One of the more popular applications of ham radio is the 2-meter FM band. With the proper radio and antenna built for the 2-meter FM band (144.0 - 148.0 Mhz), you will be able to communicate over the airwaves with an FM signal through your coaxial-fed transmission line. FM signals are limited to line of sight, so communication will be restricted to a few miles in your local area. Following a few steps will help you to know how to make a coaxial FM transmission antenna.

Things You'll Need

Soldering gun
Solder
Flux
Wire Cutters
Measuring tape
Table vise
Needle nose pliers
Sandpaper (80 grit)
Screwdriver
Copper wire (bare)
SO-239 connector
4 stainless steel bolts and nuts (#6)

Instructions

- 1
  Using the wire cutters and measuring tape, measure and cut four copper wires to 20 3/16 inches. Measure and cut one copper wire to 19 5/16 inches. Each of these cut wire will now be the elements for the antenna. Make sure each wire is as perfectly straight as possible to form a copper rod.
- 2
  Using the sandpaper to sand one end of each of the five copper rods/wires to remove any finish and take them down to the bare shiny copper.
- 3
  Mount the SO-239 in the table vise, with the male pin pointed up for access to solder. Do not over-tighten the vise and damage the connector.
- 4
  Apply a small amount of flux to the sanded end of the rod that measures 19 5/16 inches and insert it into the hollow end of the male pin on the SO-239 connector. Hold steady in place as you solder in the step below.
- 5
  Using the soldering gun, apply solder to the tip of the connector pin and the rod evenly, around all sides, in order to solder them together. Apply just enough solder to make a secure connection. Do not overheat the connector and risk melting the plastic insulator inside the end of the connector. Allow the solder to cool for a couple of minutes before moving on.
- 6
  Bend a small loop in the sanded end of each of the remaining copper rods with the needle nose pliers.
- 7
  Remove the SO-239 connector from the table vise.
- 8
  Mount one of the four copper rods to the four corners of the connector using the screwdriver, bolts and nuts. Tighten the bolts and nuts to a snug fit.
- 9
  Holding the SO-239 connector at eye level, use the pliers to bend the four rods from Step 8, downward to about an 45 degree angle.
- 10
  Connect the coaxial cable from your 2-meter FM transceiver to the female end on the SO-239 connector. The male connector on the coaxial cable from your radio to the antenna is called a PL-259 connector.
- 11
  Apply a liberal amount of clear silicone to the top of SO-239 connector and to where the PL-259 connector screws in the bottom of the SO-239. Allow several hours to dry, as directed by the manufacture guidelines on the tube of silicone. The silicone will help prevent moisture and rain from damaging the connector by getting into the coaxial feed line.

Ham Radio