SSR Flashcards
How does the SSR ground/air base system is similar but differ from DME?
SSR requires active co-operations of an aircraft in that it must be equipped with an air traffic control transponder, the system is similar to DME in this case the ground based transmitter/receiver is the interrogator and the aircraft the transponder.
At what frequency band does SSR operate?
UHF
At what frequency does the ground interrogator transmit and receive?
The ground interrogator transmits on 1030MHz and receives on 1090MHz
At what frequency does the aircraft transponder transmit and receive?
The aircraft transponder receives on 1030MHz and transmit on 1090HZ
How many modes does the SSR have?
4
How can side lobe affect SSR?
The directional signal transmitted from the main lobe of the SSR antenna is. much stronger than any of the side lobe signals, but a side lobe signal may interrogate the aircraft transponder when the main lobe is not directed at the aircraft, especially if the aircraft is close to the transmitter.
How does side lobe suppression P1, P2 and P3 prevent side lobes interrogating a transponder?
The transponder is able to compare the amplitudes of P1-P3 pulses with that of P2. If P1 and P3 are greater than P2 the transponder will recognise this as a correct interrogation and generate a reply.
If P2 is greater than P1 and P3 the transponder will recognise this as a side lobe interrogation and suppress the reply transmission.
Which pulse number is the SLS pulse?
P2
How is the de-fruiting work?
De-fruiting is achieved by operating adjacent interrogators at different PRF’s, whilst electronic de-fruiting circuits are used to correlate transponder replies to ensure that only correct replies are supplied to the interrogating.
What is the range of SSR?
Line of sight, 200nm.
What is the SSR spacing between interrogation pulses of Mode A, B and C.
8, 17, 21, 25
SSR modes:
The aircraft is interrogated from the ground station by a predetermined series of pulses on
the carrier frequency of 1030 MHz; its transponder then transmits a coded reply on a carrier
frequency of 1090 MHz. The two main modes of operation are:
• Mode A - an interrogation to identify an aircraft
• Mode C - an interrogation to obtain an automatic height read-out of an aircraft
The difference between modes of the SSR:
- Mode A - an interrogation to identify an aircraft
* Mode C - an interrogation to obtain an automatic height read-out of an aircraft
The usable numbers on an SSR ranges from -
0 - 7
With Mode C enabled, the controller can view the aircraft altitude in increments of?
And refenced above?
100ft
QNE
