Figure 14-41.  Phonetic alphabet.  If radio communication is lost, it may be a prudent decision  to land at a non-towered airport with lower traffic volume, if  practical. When operating at a non-towered airport, no radio  communication is necessary. However, pilots should be extra  vigilant when not using the radio. Other traffic may not as  The ATC radar beacon system (ATCRBS) is often referred to  as “secondary surveillance radar.” This system consists of three  components and helps in alleviating some of the limitations  associated with primary radar. The three components are an  interrogator, transponder, and radarscope. The advantages of  ATCRBS are the reinforcement of radar targets, rapid target  identification, and a unique display of selected codes.  Growing air traffic in the National Airspace System (NAS)  will be addressed through the use of ADS-B, which not only  The characteristics of radio waves are such that they normally  travel in a continuous straight line unless they are “bent” by  atmospheric phenomena, such as temperature inversions,  reflected or attenuated by dense objects such as heavy clouds  and precipitation, or screened by high terrain features. Radar  signals degrade over distance, cannot penetrate through solid  objects such as mountains, and the fastest radar updates every  4.7 seconds. By contrast, the satellite signals used with  Automatic DGLYPH<df00>pGLYPH<df00>ndGLYPH<df00>nt SurvGLYPH<df00>illancGLYPH<df00>−Broadcast (ADS−B) do not degrade over distance, provide better visibility around  mountainous terrain and allows equipped aircraft to update  their own position once a second with better accuracy.  Modern radar is very reliable and there are seldom outages.  This is due to reliable maintenance and improved equipment.  There are, however, some limitations that may affect ATC  services and prevent a controller from issuing advisories  concerning aircraft that are not under his or her control and  cannot be seen on radar.  Radar is a device that provides information on range, azimuth,  and/or elevation of objects in the path of the transmitted  pulses. It measures the time interval between transmission and  reception of radio pulses and correlates the angular orientation  of the radiated antenna beam or beams in azimuth and/or  elevation. Range is determined by measuring the time it takes  for the radio wave to go out to the object and then return to the  receiving antenna. The direction of a detected object from a  radar site is determined by the position of the rotating antenna  when the reflected portion of the radio wave is received.  Besides the services provided by an FSS as discussed in  Chapter 12, “Aviation Weather Services,” numerous other  services are provided by ATC. In many instances a pilot  is required to have contact with ATC, but even when not  required, a pilot may find their services helpful.  easily be aware of your presence when they are expecting  the standard radio calls.  Air Traffic Control (ATC) Services  Primary Radar  ATC Radar Beacon System (ATCRBS)  14-24  Morse Code  Telephony  Phonic Pronunciation Character  r R 0 q Q 9 p P 8 o O 7 n N 6 5 5 4 4 3 3 2 2 1 1 z Z Y y x X w W V U v V u t T T s S S r R Q P q p o O n N M m L L L k K j J J i I I h h H g G f F e E d D c C B b a A