Written by Ernest Werbel on June 4, 2023

When a piece of coaxial cable is not grounded at one end and passed through a ferrite core, it can act as a single turn transformer in RF (radio frequency) circuits because the ferrite core can concentrate the magnetic flux of the RF signal passing through the cable.

The coaxial cable consists of two conductors, a center conductor, and an outer conductor, which are separated by an insulating material. When an RF signal is applied to the center conductor, it creates an electromagnetic field that surrounds the center conductor.

When the coaxial cable is passed through a ferrite core, the core can act as a magnetic transformer. The ferrite material has high magnetic permeability, which means that it can concentrate the magnetic flux of the RF signal. As the RF signal passes through the ferrite core, the magnetic field of the signal is concentrated in the core, which creates a magnetic flux.

The magnetic flux then induces a current in the outer conductor of the coaxial cable, which creates a voltage across the cable. This voltage can be used as a signal in the RF circuit.

The ferrite core acts as a single turn transformer because the coaxial cable is effectively a single turn coil. The outer conductor of the coaxial cable acts as the secondary winding of the transformer, and the ferrite core acts as the primary winding. The amount of voltage induced in the outer conductor depends on the strength of the magnetic flux in the ferrite core and the length of the cable passing through the core.

Overall, the use of a ferrite core can help to increase the efficiency and effectiveness of RF circuits by allowing for the creation of a voltage signal through the use of a simple and compact transformer design.