Helical uhf transmitting and/or receiving antenna

Claim 1

A helical UHF transmitting and/or receiving antenna for electromagnetic waves in the frequency range of between 400 MHz and 1000 MHz, the waves having wave lengths, the antenna including a wire having the shape of a helix, the helix having an axis and a height, the helical wire being mounted within a closed housing which is permeable to HF radiation, a coaxial connector for supplying a UHF signal to an end of the helical wire, the helix having between one and a half of ten turns, the helical wire having a diameter, a height and a total length which are substantially smaller than the wave lengths, means for continuously changing the height of the helix by at most onethird of its height, the means for continuously changing the height of the helix comprising a rod having a fine thread extending in the axis of the helix, and a cap-shaped trimming disk having a fine thread and being rotatable on the rod, the trimming disk being movable on the rod in axial direction of the rod, further comprising a wing nut rotatably mounted on the rod and rigidly connected to the trimming disk, means for locking the trimming disk against torsion force of the helical wire, the helical wire having two ends, a base plate fixedly attached to one of the ends of the helical wire remote from the trimming disk, the base plate and the trimming disk having solder sleeves, the helical wire being attached by means of solder connections to the solder sleeve of the base plate and the trimming disk, wherein rotation of the wing nut results in continuous change of the diameter of the helical wire, wherein the trimming disk and the rod are of high-grade HF insulating material.