A rabbit ears antenna is what is known as a half-wave dipole antenna. The electromagnetic field that propagates the transmitted RF (Radio Frequency) signal induces a standing wave into the antenna. The magnitude of the standing wave (seen as signal strength) is dependent on many factors, one of which is the combination of the polarization of the RF signal relative to the orientation of the antenna.

Television broadcasts use horizontal polarization (the electric field component is oriented parallel to the earth's surface); there are some stations that use "elliptical" polarization, but the vast majority of the power is still in the horizontal orientation - only a relatively small amount of power goes into vertical polarization.

Because the television signal has horizontal polarization, the best position for the antenna "ears" is also horizontal, and perpendicular to the signal source. If the "ears" are vertical or are pointed directly at/away from the signal source, very little current will be induced in the antenna, and the received signal will be very weak.