A microwave ablation catheter is provided. The microwave ablation catheter includes a coaxial cable connected at its proximal end to a microwave energy source and at its distal end to a distal radiating section. The coaxial cable includes inner and outer conductors and a dielectric positioned therebetween. The inner conductor extends distally past the outer conductor and is in sealed engagement with the distal radiating section. A balun is formed in part from a conductive material electrically connected to the outer conductor of the coaxial cable and extends along at least a portion of the coaxial cable. The conductive material has a braided configuration and is covered by at least one insulative material.