A balun at the centre of a dipole: what the NanoVNA proved, and what it did not
· 10 min read
The antenna from the previous note — two legs of twisted pair, about twenty metres each, six metres up — worked beautifully on receive. What did not work was the place where the wire meets the cable. To begin with there was a twisted joint and insulating tape: a solution that lasts until the first rain and does not hold electrically at all.
On 8 December 2023 I built a proper centre: a balun on a ferrite toroid inside a sealed box. And, more to the point of this note, I checked it with an analyser — and then worked out that I had checked something other than what I thought.