What It Looks Like

Aircraft antennas seem to come in as many shapes, sizes, varieties, and locations as the airplanes on which they are mounted. The simple reason for all of those variables is the variety of functions and frequencies of the avionics that the antennas feed.

Last month we looked at VHF com (communications) antennas, which are optimized by length to transmit and receive in the VHF communications frequency range - 118 to 137 MHz.

VHF nav antennas, on the other hand, are optimized to receive VOR and localizer signals in the 108 to 118 MHz range. (A localizer signal enables a pilot to track an extended runway centerline on an instrument approach. A glide-slope signal provides vertical guidance to the runway. An instrument approach with both localizer and glideslope is a precision approach or ILS, for instrument landing system.)

One of the two most popular types of VOR/LOC nav antennas, with two thin wire strands extending in a V shape from near the top of the vertical fin, is commonly called a cat's whisker antenna, for obvious reasons. The other common type, shown above, is the more robust antenna often referred to as a towel bar antenna because, well, you get the idea.