M0VAI's BALUN PAGE
During the summer of 2010 the club decided to take part, for the first time, in the annual RSGB NFD SSB Contest. As we put the wheels in motion to gather all the necessary equipment we found ourselves wondering what kind of antenna we are going to use. After a few weeks of intense discussion we decided that a multiband wire antenna will be the one, and it was down to me to construct it.
The antenna is a doublet for 80m – 10m (135 feet approximately) fed with twin line feeder (I used 450 ohm ladder line), it is very simple, yet very effective and efficient multiband antenna.
The advantage of using ladder line is that you have lower loss even with high SWR and long runs. Because we needed to use the internal automatic tuner of the radio I had to construct a suitable balun to connect the twin line feeder to the radio.
The design I used is from an article that I found on the RSARS website and written by Mario G8ODE.
LINK TO VERSATILE BALUN PDF13 turns of 1.6mm enamelled copper wire tri-filer wound on to an Amidon red T-200 toroid.
I wrapped the toroid with fibreglass tape to protect it and housed the balun in an IP56 case.
The balun performed exceptionally well during the contest with no signs of overheating.
73 Dimitris previous 2E0DIM current M0VAI
