An electrosurgical device, comprising: a coaxial feedline having an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a dielectric material disposed therebetween; an elongated electrically-conductive member longitudinally disposed at a distal end of the inner conductor; a balun structure ("B") disposed on the outer conductor and including a dielectric layer coaxially disposed around a distal portion of the outer conductor and an electrically-conductive layer (430; 630) coaxially disposed around a proximal portion of the dielectric layer, the dielectric layer extending distally beyond a distal end of the electrically-conductive layer (430; 630) to direct electrical current into the balun structure ("B"); an electrically-conductive cylinder (540; 640; 940) coaxially disposed around a distal portion of the balun structure; a dielectric structure disposed substantially adjacent to a distal end of the electrically-conductive cylinder, wherein the dielectric structure longitudinally extends from the distal end of the electrically-conductive cylinder to a distal end of the electrically-conductive member; an elongated handle assembly coaxially disposed around a portion of the outer conductor at a distal end of the coaxial feedline, wherein the handle assembly is disposed proximal to the dielectric structure; and a shell assembly (1240; 1340) disposed at a distal end of the elongated handle assembly, wherein a portion of the shell assembly extends distally beyond the distal end of the electrically-conductive member, wherein the shell assembly includes an inner portion and an outer portion, wherein the outer portion includes an electrically-conductive material and the inner portion includes layers with dielectric materials having varying dielectric constants so as to direct the radiation. a coaxial feedline having an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a dielectric material disposed therebetween; an elongated electrically-conductive member longitudinally disposed at a distal end of the inner conductor; a balun structure ("B") disposed on the outer conductor and including a dielectric layer coaxially disposed around a distal portion of the outer conductor and an electrically-conductive layer (430; 630) coaxially disposed around a proximal portion of the dielectric layer, the dielectric layer extending distally beyond a distal end of the electrically-conductive layer (430; 630) to direct electrical current into the balun structure ("B"); an electrically-conductive cylinder (540; 640; 940) coaxially disposed around a distal portion of the balun structure; a dielectric structure disposed substantially adjacent to a distal end of the electrically-conductive cylinder, wherein the dielectric structure longitudinally extends from the distal end of the electrically-conductive cylinder to a distal end of the electrically-conductive member; an elongated handle assembly coaxially disposed around a portion of the outer conductor at a distal end of the coaxial feedline, wherein the handle assembly is disposed proximal to the dielectric structure; and a shell assembly (1240; 1340) disposed at a distal end of the elongated handle assembly, wherein a portion of the shell assembly extends distally beyond the distal end of the electrically-conductive member, wherein the shell assembly includes an inner portion and an outer portion, wherein the outer portion includes an electrically-conductive material and the inner portion includes layers with dielectric materials having varying dielectric constants so as to direct the radiation.