"Rabbit ears" is a common term for a very simple type of television antenna, the dipole antenna. They are called "rabbit ears" because they look like a pair of rabbit ears springing out from the top of the television set. They consist of two metal rods coming out at an angle from a set-top device.
The earliest dipole antenna was created in 1886, by Heinrich Hertz, one of the early pioneers of electromagnetism. The "rabbit ears" antenna came not long after the advent of television broadcasts, as a way to boost signal and get better reception. "Rabbit ears" are basically just a dipole antenna that has adjustable angles and lengths, allowing the user to fine tune their antenna to get the best reception. This will depend on the atmospheric conditions, their location, and the strength of the broadcast signal. Some "rabbit ears" antenna include a small loop at the base to help with UHF reception, and others have dials built in which allow for a fine-tuning of the antenna itself.
For many years the "rabbit ears" antenna setup was the quintessential way to improve reception to a television set, and many tricks were developed to improve how well they worked. For example, "rabbit ears" are very susceptible to interference from other electronic devices that emit an electromagnetic field, and so keeping them away from these devices is very important. Computers, fish tank pumps, fluorescent lights, cordless phones, and any number of things can interfere with the antenna reception.
In fact, while the traditional placement of "rabbit ears" was to put them right on top of the television set, in modern times this is no longer ideal. This is because most modern televisions include computers which can interfere with the functioning of the antenna. For this reason, many people recommend connecting the antenna via coaxial cable, so that the "rabbit ears" themselves can be placed a suitable distance from the television.
With the advent of cable television and satellite television, the "rabbit ears" setup diminished in use and importance in the United States. For much of the late-1990s and the early part of the 21st century it appeared that these antennas would no longer be used, except in extremely rural areas, or by those who didn’t wish to subscribe to cable and satellite. It seemed like the end of the line for a technology that had been around since the beginning of television, and then, in early 2009, broadcast television made the switch to high-definition television.
High-definition television offered over the air has a number of benefits from traditional analog broadcasts, including the fact that the picture never gets snowy: it either comes in, or it doesn’t. This means that many people can now receive high-definition television that rivals cable or satellite picture quality, through their everyday television set. And the "rabbit ears" antenna setup, modified with a ring to receive UHF signal, can help boost a set’s ability to receive an HDTV signal. And so now it is not an uncommon site to see an expensive high-definition television set with a fairly simple, $40 US Dollar set of "rabbit ears" attached.