2018-03-19
Building my own balun, part 1: idea and parts needed 2 months ago
I was considering hanging a dipole antenna outside. This would need a balun and I realized that I have a good outdoor-capable balun hanging in the attic. It's a Fritzel 1005 1:1 current balun which is good up to 300 watts power. I am not going to use 300 watts under the roof close to other equipment and the balun there does not need to be rain proof. So the idea was born to build a smaller balun for use under the roof and have the Fritzel balun available for outdoor use. And last Saturday was a hamfest (radio onderdelenmarkt Rosmalen) so I had an idea of things I wanted for this project. Parts needed for a current balun:The various collections of electronics parts only missed the SO239 socket and a case. Those were found at the hamfest for a nice price. The choice of design is a current balun or a voltage balun. I had to do some searching to find a good comparison between the two, and DX engineering has one at Baluns: Choosing the Correct Balun - DX Engineering which has:
- A ferrite core with the right specifications
- Wire with enamel coating
- An SO239 socket
- Terminals for connecting the dipole wires
- A case
Current baluns, rather than voltage baluns, should be used whenever possible. Current baluns provide better balance and often have lower loss. Current baluns, especially 1:1 ratio baluns, tolerate load impedance and balance variations much better than voltage baluns.Some searches found good explanations of building your own baluns, I found a very clear explanation at VK6YSF project page. So I'm building a current balun, and when it's finished enough to test it I will measure how it is doing. I have the tools like the SARK100 antenna analyzer that I can control from Linux and a dummy load so I can check everything. Other parts:
- Building my own balun, part 2: measuring the 'old' balun
- Building my own balun, part 3: First work on the case
- Building my own balun, part 4: Deciding on where to put dipole ends and finishing it
- Building my own balun, part 5: First tests of the result
- Building my own balun, part 6: Redo and some success: a working antenna again
- Building my own balun, part 7: Better measurements of the result