The area toward which the primary reflector directs and concentrates the signal. Ideally the receive focal point is at the receive horn assembly. Transmissions from satellite dishes have a transmit focal point that coincides with the position of the satellite. The area on the earth's surface where reception characteristics for a particular satellite and transponder are optimal. This is based on the EIRP of the signal from a given satellite and transponder and different transponders on the same satellite will often have different footprints of signal strength.
Reception deteriorates gradually from the center of the footprint.
Depending on variable factors such as positioning and type of feed assembly satellite footprints may be roughly circular or elliptical in shape. In elliptical configurations some transponders are aimed off-center in order to provide a wider coverage area. Footprints may change over the course of time as the satellite ages and orbital orientation drifts. Frame One complete video picture. In NTSC, takes place in one-thirtieth of a second and is made up of 525 lines and two fields.