How do you know if your Huey is “old school?” It has a pair of “cat’s whisker” antenna mounted in the nose.
The four vertical whips protruding from their horizontal bases were attached to the helicopter’s FM radio and could be used for talking to, or homing in on, friendly ground forces who were out of sight below.
Troops on the ground could key their radio set and a Huey pilot could fly toward the strongest FM squeal sound. Approach from a couple different angles and a Huey crew could figure out where the friendlies were below them in the jungle.
Later versions of the Huey do not have the whiskers. A different version of the antenna, mounted on the roof of the Huey’s cabin, was dubbed the “towel bar” and worked similarly.