Here’s a 1:1 current balun I wound for the folded ‘skeleton sleeve’ 40m/20m dipole antenna that we’re building for our second Field Day antenna:
It may not look a big deal, but it actually is. Its functions in life are two-fold:
- to ‘choke’ off common mode currents flowing on the outside of the coax feed line braid that could enter the shack (bad news)
- provide a transition from the BALanced antenna to the UNbalanced coax feed line (good news)
Here’s what it looks like housed in its plastic box:
The plate to the right is specially designed to accommodate 450 ohm ladder line with full strain relief. In this antenna, the ladder line is the antenna, not the feed line. Coax is attached to the SO-239 socket at the left and fed back to the operating position.
Want to learn more about the skeleton dipole and baluns? Of course you do:
Simple explanation of balun theory and construction:
And if you’re really, really interested in balun theory, here’s the definitive guide from W7EL:
Don’t forget: Tuesday, May 16 at 7pm, Red Cross House.
I’ll be talking all about Field Day with slides and demonstrations at the WARA May meeting. If you’re coming along to Field Day (you are, right?), I would strongly recommend you attend.
73. Steve, VA7KH