QRP Balun
Constructing a simple QRP choke balun for HF using common junk box components.
Description
The QRP choke balun described utilizes a high permeability ferrite rod and RG-174 coax, aiming to present high impedance to common-mode currents across the HF spectrum. The construction involves winding as many turns of RG-174 as possible around the ferrite rod, then encapsulating the assembly with hot glue. This design prioritizes maximizing inductance to suppress unwanted shield currents, particularly in unbalanced antenna configurations.
While the balun's effectiveness is subjectively reported as good, a potential design consideration involves the dielectric properties of the hot glue. This material could increase turn-to-turn capacitance, potentially reducing the balun's performance at higher HF frequencies, though this specific aspect has not been formally tested by the author, AA5TB.
The project serves as an illustrative example of a practical, junk-box construction rather than a rigorously engineered solution. Photographs detail the evolution of the balun, from the initial winding process to its integration within a B&W dipole center insulator and final camouflaged assembly.