Secondary Surveillance Radar Flashcards
What info can be presented to ATC from SSR
Pressure Altitude
Flight Level
Flight number/AC reg
Ground Speed
Principal of SSR
Radar antenna rotates and transmit a pulse which is received by ac transponder.
Transponder sends back a reply containing a code (Mode A) or (Mode C) or (Mode S)
Frequency’s of SSR
Interrogation sends out frequency 1030 MHz
Aircraft Transponder reply’s on 1090 MHZ
60 MHz difference
Special Position Identification
When IDENT button pressed on transponder - begins to flash on the display of the controller
Pulse Train
A series of pulses which carry information from transponder to interrogator
What Frequency band is SSR
UHF Band
What three pulses are transmitted to differentiate between interrogations
P1
P2
P3
Mode A - 2 Microsecond between P1 and P2
Mode C - 21 Microsecond between P1 and P2
How does the transponder detect mode of interrogation
The time interval between the pulses P1 and P3 that determines the mode of interrogation
What is the function of P2
Avoid responses from side lobes
If P2 signal is stronger than the interrogation pulse the response is denied - only replies to interrogation by the main beam
Side Lobe Suppression
Mode c
Provides pressure altitude info. 100ft increments used for vertical separation
Mode S
Better performance than mode C
Altitude reports with an accuracy of 25ft
Selective Addressing
24 bit code providing over 16 million hard coded addresses
Mode A and C are limited to how many codes
4096
P1/P2/P3/P4
InterMode A/C/S All call - P1/,P2,P3 and Long p4
InterMode A/C - P1,P2,P3 and short P4
Vertical increments of mode c and s
Mode C - 100ft
Mode S - 25ft
When the ident button is pressed what happens
Transponder transmit the additional pulse at the end of the normal pulse train
