The article Low power Guanella 1:1 balun with low Insertion VSWR using a Fair-rite 2843009902 binocular – design workup describes a current balun with low Insertion VSWR for operation at modest power levels. The design was based on a low cost Fair-rite 2843009902 binocular core (BN43-7051).
This article documents measurement of the complex common mode impedance Zcm, and calibration of the predictive model.
Zcm is a most useful quantity, it can be used in NEC models of an antenna system.
Measurement of common mode impedance
Common mode impedance was measured using a nanoVNA.
The response is quite similar to previously modelled, but self resonant frequency (SRF) is a little lower, so the model needs calibration.
Calibration of model
The model was calibrated by increasing Cs to 2.9pF to achieve SRF=9.4MHz.
The next step is to measure temperature rise (take thermographs) under measured common mode current.
- Duffy, O. Feb 2007. A model of a Guanella 1:1 choke balun using two Jaycar LF1260 cores.
- ———. 2008. A model of a practical Guanella 1:1 balun. https://owenduffy.net/files/GuanellaBalun01.pdf.
- ———. Mar 2012. Common mode choke design tool.
- ———. Apr 2016. Low power Guanella 1:1 balun with low Insertion VSWR using a pair of Jaycar LF1260 suppression sleeves.