The W2DU Choke Balun
This is an extremely effective type of choke balun originally designed by M. Walter Maxwell, W2DU, and consists of a number of ferrite cores slid over a length of coaxial feeder. The cores present a high impedance to any RF current that would otherwise flow on the outside of the coax shield. The 1-1 impedance ratio of this balun remains fairly constant over a wide frequency range. The ferrite has to be the correct type to avoid heating, and to provide the necessary frequency coverage.

The W2DU balun is capable of handling over 3 kW at SWRs up to 2-1. It is potted in a thermoplastic sleeve, with a military spec.PL-259 (silver plated body & PTFE insulation) at one end for connection to the feeder, and a pair of tails fitted with terminals to connect to the antenna at the other. This balun is completely weather proof.

          Specifications

• W2DU - choke balun
• Power Handling - 3Kw
• Connectors - crimped lugs on flying leads, approx 6" output of RG213 type cable with fitted PL259 plug