Using Ferrite E-cores for Baluns in Ham Radio Applications

This article by Chavdar Levkov LZ1AQ, published on October 3, 2021, details the application of ferrite E-cores for constructing baluns. E-cores and U-cores are presented as cost-effective options, particularly useful when connectors are already mounted on cables, as they allow winding multiple turns without dismounting connectors. The material of E-cores is generally suitable for common mode baluns up to 15 MHz. They are recommended for baluns on control and power supply cables where very high common mode impedance is not a primary requirement. The article suggests old switch-mode power supplies as a source for junk box E-cores. Examples include a balun on a USB cable using a Ferroxcube E 32x16x9, 3F3 core with 4 turns, secured by three cable ties. Another example shows a balun with 8 turns of shielded cable with RCA connectors on the same core, achieving 140 uH inductance at low frequencies. The impedance plot for this example is measured between the shield ends. The article includes figures illustrating these examples.