TM  55-1510-221-10 Do  not  operate  the  weather  radar  set  in  a confined   space   where   the   nearest   metal wall  is  50  feet  or  less  from  the  antenna reflector.   Scanning   such   surfaces   may damage  receiver  crystals. (1.) Turn-on  procedure:  Function  switch  - TEST  or  ON,  as  required.  (Information  will  appear after  time  delay  period  has  elapsed.) (2.)   Initial   adjustment   operating   proce- dure: 1. BRT  control  -  As  required. 2.   MODE   switches   -   Press   and release  as  required. 3.  RANGE  switches  -  Press  and release  as  required. 4. TILT  control  -  Move  up  or  down to  observe  targets  above  or  below aircraft   level.   The   echo   display will  change  in  shape  and  location only. (3.)  Test  procedure: 1. Function  switch  -  TEST. 2.   RANGE   switches-   Press   and release   as   required   to   obtain   80- mile  display. 3. BRT  control  -  As  required. 4.   Screen    -   Verify   proper   display. (The   test   display   consists   of   two green   bands,   two   yellow   bands, and   a   red   band   on   a   120-degree scan.  The  word  TEST  will  be  dis- played   in   the   upper   right   comer. The   operating   mode   selected   by the  MODE  switches,  either  MAP, WX,   or   WXA,   will   be   displayed in  the  lower  left  corner.  If  WXA has  been  selected,  the  red  band  in the  test  pattern  will  flash  on  and off.  The  range  will  be  displayed  in the  upper  right  corner  beneath  the word  TEST  and  appropriate  range mark   distances   will   appear   along the  right  edge  of  the  screen.) (4.)  Weather  observation  operating  proce- dure: 1. Function  switch  -  ON. 2. 3. 4. 5. 6. MODE   switches   -   Press   and release  as  required  to  select  WX. BRT  control  -  As  required. TILT   control -   Adjust   until weather  pattern is   displayed. Include   the   areas   above   and below  the  rainfall  areas  to  obtain a  complete  display. MODE   switches   -   Press   and release   to   select   WXA.   Areas   of intense   rainfall   will   appear   as flashing  red.  These  areas  must  be avoided. TRACK  switches  -  Press  to  move track   line   through   area   of   least weather   intensity.   Read   relative position   in   degrees   in   upper   left corner  of  screen. NOTE Refer   to   FM   1-30   for   weather   observa- tion,   interpretation   and   application. (5.) Ground   mapping   operating   procedure: 1. Function  switch  -  ON. 2.  MODE  switches  -  Press  and release  as  required  to  select  MAP. 3. BRT  control  -  As  required. 4.   GAIN   control   -   As   required   to present  usable  display. (6.)  Standby  procedure:  Function   switch   - STBY. (7.)  Shutdown  procedure:  Function  switch - OFF. (8.)   Weather   radar   emergency   operation. Not   applicable. 3-32. TRANSPONDER SET (APX-100). a.  Description. The   transponder   system receives,   decodes,   and   responds   to   interrogations from  Air  Traffic  Control  (ATC)  radar  to  allow  air- craft  identification, altitude   reporting,   position tracking, and  emergency  tracking.  The  system receives  a  radar  frequency  of  1030  MHz  and  trans- mits  preset  coded  reply  pulses  on  a  radar  frequency of  1090  MHz  at  a  minimum  peak  power  of  200 watts.  The  range  of  the  system  is  limited  to  line-of- sight. 3-78