TUNABLE SPIRAL ANTENNA Russian patent published in 1997 - IPC

FIELD: transceiving antennas for portable USW radio sets. SUBSTANCE: tunable spiral antenna has two spiral elements; first spiral element has its lower end forming, together with radio facility, antenna input and upper open end functioning as main radiator of antenna; second spiral element is arranged coaxially to first one and isolated from the latter; its diameter and winding pitch are same as those of first spiral element; it is placed at top end of first spiral element so that part of its turns are placed between turns of first element and second element is free to displace relative to first one by turning about common axis. This displacement provides for tuning antenna to desired frequency. EFFECT: simplified design, improved power characteristics, facilitated tuning to desired frequency. 3 dwg