VK5ZVS - Balun box #1

VK5ZVS

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Need a particular balun?
Final products
Having various baluns already made with connectors, allows for quick testing.

Balun construction.

The various baluns are made with 2 x ferrite cores, Jaycar LF1258 taped together to form a figure eight core (side view). The wire used is from Category 5 data cable. The type of wire provides good insulation between wires and allows the correct amount of interwinding capacitance between the turns to give us the desired response characteristics we're looking for in a balun.

More details to follow .......

6 to 1 balun.
The completed balun core - wired.
This balun was made with two ferrite cores, (Jaycar LF1258)wired using Cat 5 UTP wire. The winding ratio is 6 turns to 15 turns. 50 ohm primary is 6 turns. The 300 ohm secondary is formed by adding 4.5 turns to either end of the primary, giving 15 turns overall. The picture here shows the balun core ready for testing. The two single wires are the 300 ohm secondary. The two twisted & soldered pairs are the 50 ohm primary. The small twisted and soldered pair is the centre tap.

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.

and the return loss?

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

4:1 and 9:1 matching balun (autotransformer).
This balun was made with two ferrite cores, as used previously. It uses an autotransformer design, hence, allows multiple taps for the different required impedances.

Here's the Smith chart for the 4:1 tapping.

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

The 4:1 return loss.

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

Here's the Smith chart for the 9:1 tapping.

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

The 9:1 return loss.

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

Another SPIRAT initiative