Furuno FR-7062 Operator's Manual page 6

SART (Search and Rescue Transponder)
A Search and Rescue Transponder (SART) may be triggered by any X-Band (3 cm) radar
within a range of approximately 8 n.miles. Each radar pulse received causes it to transmit
a response which is swept repetitively across the complete radar frequency band. When
interrogated, it first sweeps rapidly (0.4 sec) through the band before beginning a rela-
tively slow sweep (7.5 sec) through the band back to the starting frequency. This process
is repeated for a total of twelve complete cycles. At some point in each sweep, the SART
frequency will match that of the interrogating radar and be within the pass band of the
radar receiver. If the SART is within range, the frequency match during each of the 12 slow
sweeps will produce a response on the radar display, thus a line of 12 dots equally spaced
by about 0.64 nautical miles will be shown.
When the radar to the SART is reduced to about 1 n.miles, the radar display may show
also the 12 respopnses generated during the fast sweeps. These additional dot responses,
which also are equaly spaced by 0.64 nautical miles, will be interspersed with the original
line of 12 dots. They will appear slightly weaker and smaler than the original dots.
Showing SART marks on the radar display
To show the SART marks only on the radar display, detune the radar receiver by the
manual tuning out of best tuning condition. This erases or weakens all normal radar ech-
oes, but, the SART marks are not erased because the SART response signal scans over
all frequencies in the 9 GHz band. When the radar approaches the SART in operation, the
SART marks will enlarge to large arcs, blurring a large part of the screen. Reduce the
sensitivity and adjust the sea clutter control of the radar.
iv
Screen A: When SART
is distant
Radar antenna
beamwidth
Position
of SART
SART mark
length
9500 MHz
9200 MHz
Sweep time
7.5 µs
95 µs
Low frequency sweep signal
Sweep
starting
Fast sweep signal
Screen B: When SART
is close
Radar receiver
bandwidth
iii