Furuno FCR-2807 Manual De Usuario

3. Radar Observation 

A Search and Rescue Transponder (SART) may be triggered by any X-Band (3 cm) radar within a range of 
approximately 8 nm. Each radar pulse received causes it to transmit a response that is swept repetitively across the 
complete radar frequency band. When interrogated, it first sweeps rapidly (0.4 µs) through the band before 
beginning a relatively slow sweep (7.5 µs) 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 nm, the radar display my show also the 12 responses generated 
during the fast sweeps. These additional dot responses, which also are equally spaced by 0.64 nautical miles, will be 
interspersed with the original line of 12 dots. They will appear slightly weaker and smaller than the original dots.  

9500 MHz

9200 MHz

Radar antenna
beamwidth

Lines of 12 dots 
are displayed in 
concentric arcs.

Echo from SART

Position of
SART

Own ship
position

Own ship
position

SART mark
length

Radar receiver
bandwidth

Sweep time

7.5 

μ

s

 95 

μ

s 

Sweep start

High speed sweep signal

Low speed sweep signal

24 NM

1.5 NM

Position of
SART

Echo from
SART