40m Antenna Project
Members of the Central Coast Amateur Radio Club met at the club on June 21 to build a 7 MHZ vertical antenna. The impetus for this build came to get a 40 meter antenna ready for the upcoming Trans-Tasman contest which we will be participating in. The antenna is easily built and doesn’t cost much. It can be adapted for portable operations.
Col and Graham sourced bamboo poles from a local supplier. Graham supplied build instructions and center loading coil formers to club members. There are plenty of poles for club members to build their own antenna. First step was to clean up the poles. Secateurs, chisels and Col’s handheld chainsaw sorted that task out. The center loaded vertical radiator was constructed and wound onto a pole. It was soldered to a connector along with some radial wires. We hoisted the antenna up onto the fence and secured it with some clamps for its first tune-up test. Peter brought his antenna analyser along which was very handy. At the first try, the dip was too low in frequency, so a turn was removed off the coil. Try again and still to low so trimmed the radiator length. By an iterative process we got the antenna to have a very low SWR across the whole 40 Meter band – success. Thanks to all who participated.
The PDF instruction sheet for this easily built antenna is available on club’s website.
