1) Radio frequency antenna type
Found on
https://www.crosswordclues.com/clue/helical-antenna
A helical antenna is an antenna consisting of a conducting wire wound in the form of a helix. In most cases, helical antennas are mounted over a ground plane. The feed line is connected between the bottom of the helix and the ground plane. Helical antennas can operate in one of two principal modes: normal mode or axial mode. In the normal mode or ...
Found on
http://en.wikipedia.org/wiki/Helical_antenna
No exact match found.
