The invention provides methods for validating a position of an airborne platform, by comparing rate of change of a measure of barometric altitude with rate of change of a measure of geometric altitude. For example, the apparatus can set a frequency of the local oscillator signal based on the selected channel. The shell covers the insulating housing and all of the terminals. The connector also includes a retaining rod extending vertically with clearance through a hole that is dead center with the center part of the hinge of the frame element.