1:1 and 4:1 Current Balun Measurements

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Normal

As expected, the SWR and Impedance are flat line traces.


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Center Conductor Short without Balun

As expected, the SWR and Impedance are unacceptable.


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Center Conductor Short with Balun

With five Palomar FSB-1/4 Ferrite Split Beads, the Balun has acceptable performance at about 6 MHz and above.


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FT140-43 Dual Core 4:1 Current Balun with one lead shorted

  • This Balun is good from about 3.5 MHz (SWR = 1.1) and up.
  • FT140-43 Balun choking Z with 9T at 3.5 MHz using Calculator = 1576 ohms
  • 3.5 MHz choking to load impedance ratio = 7.9:1


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Plot with limit unbalance.

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20 MHz with limit unbalance.

FT140-61 Dual Core 4:1 Current Balun with one lead shorted

  • FT140-61 Balun choking Z with 9T at 20 MHz using Calculator = 1527 ohms
  • 20 MHz choking to load impedance ratio = 7.6:1


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Normal plot

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Plot with limit unbalance.

BN43-202 with 1:1 Baluns on both cores


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Normal plot

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Plot with limit unbalance.

BN43-202 with each 1:1 Baluns on separate core


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Normal plot

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Plot with limit unbalance.

BN43-7051 3T 4:1 Balun


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Plot with limit unbalance.

RG-8X Coax Coil Balun, 4" diameter, 10 Turns

  • Balun choking Z at 6 MHz (~11 uh) = 415 ohms
  • 6 MHz choking to load impedance ratio = 8.3:1


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Limit unbalance at 1.1:1 SWR 4 MHz.

Five FB-43-1020 Beads

  • Balun choking inductance at 4 MHz using Chart = 3.2 uH x 5 = 16 uH
  • Balun choking Z at 4 MHz = 402 ohms
  • 4 MHz choking to load impedance ratio = 8:1