Figure 11-2.  Bomber onboard radio station.  navigational equipment for aircraft. The space program began  and added a higher level of communication and navigational  necessity. Communication satellites were also launched. The  Cold War military build-up caused developments in guidance  and navigation and gave birth to the concept of using satellites  for positioning.  In the 1970s, concept-validation of satellite navigation was  introduced for the military and Block I global positioning  system (GPS) satellites were launched well into the 1980s.  Back on earth, the long-range navigation system (LORAN)  was constructed. Block II GPS satellites were commissioned  in the mid-80s and GPS became operational in 1990 with the  full 24-satellite system operational in 1994. In the new millennium, the Federal Aviation Administration  (FAA) assessed the national airspace system (NAS) and  traffic projections for the future. Gridlock is predicted  by 2022. Therefore, a complete overhaul of the NAS,  including communication and navigational systems, has been  A digital electronic representation of a real-world event is  discontinuous. The essential characteristics of the continuous  event are captured as a series of discrete incremental values.  Electronically, these representative samplings are successive  chains of voltage and non-voltage signals. They can be  transported and manipulated in electronic circuits. When  the samples are sufficiently small and occur with high  frequency, real-world phenomenon can be represented to  appear continuous.  Since the flow of electricity through the microphone is  continuous, the sound continuously modifies the electric  signal. On an oscilloscope, an analog signal is a continuous  curve.  [Figure 11-3]  An analog electric signal can be modified  by changing the signal’s amplitude, frequency, or phase. Electronic devices represent and manipulate real-world  phenomenon through the use of electrical signals. Electronic  circuits are designed to perform a wide array of manipulations.  Analog representations are continuous. Some aspect of an  electric signal is modified proportionally to the real-world  item that is being represented. For example, a microphone  has electricity flowing through it that is altered when sound  is applied. The type and strength of the modification to the  electric signal is characteristic of the sound that is made  into the microphone. The result is that sound, a real-world  phenomenon, is represented electronically. It can then be  moved, amplified, and reconverted from an electrical signal  back into sound and broadcast from a speaker across the  room or across the globe. For the past few decades, avionics development has increased  at a faster pace than that of airframe and powerplant  development. This is likely to continue in the near future.  Improvements to solid-state electronics in the form of micro-  and nano-technologies continue to this day. Trends are toward  lighter, smaller devices with remarkable capability and  reliability. Integration of the wide range of communication  and navigational aids is a focus.  developed and undertaken. The program is called NextGen.  It uses the latest technologies to provide a more efficient and  effective system of air traffic management. Heavily reliant  on global satellite positioning of aircraft in flight and on the  ground, NextGen combines GPS technology with automatic  dependent surveillance broadcast technology (ADS-B) for  traffic separation. A large increase in air system capacity is  the planned result. Overhauled ground facilities accompany  the technology upgrades mandated for aircraft. NextGen  implementation has started and is currently scheduled through  the year 2025.  Fundamentals of Electronics Analog Versus Digital Electronics 11-3