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1 to 1 balun.
Inside the enclosure.

The balun is constructed from Category 5 UTP data cable and half a 180mm broadcast ferrite rod. Normally, twisted pair is about 100 ohms. If you are careful and twist one pair with two single strands from another pair, to make a quad, the impedance approaches 50 ohms (when you join the diagonal opposite wires). Ideal for what we want. The tighter the overall twist, the better. The rod was tacked in place with hot melt glue. Kwik Grip is used to stop the nuts on the connectors from spinning and coming loose. I used 14 turns (quad) spaced over 70mm.
1 to 1 Balun interior
So, what does the balun's impedance look like?

Here's the Smith chart showing the impedance from 1 to 50MHz. The marker is at 30MHz.
1 to 1 Smith chart
and the return loss?

Here's the VSWR from 1 to 50MHz. The marker is at 30MHz.
1 to 1 vswr
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