Furuno FR-10, Operator'S Manual

Page: 99 / 171

3. HOW TO INTERPRET THE RADAR DISPLAY
3-5
3.2.4 Shadow sector
Funnels, stacks, masts, or derricks near the antenna interrupt the radar beam, and a
non-detecting sector can occur. Targets can not be detected within this sector.
3.3 SART (Search and Rescue Transponder)
3.3.1 SART description
When any X-band radar reaches within a range of approximately 8 nm, a Search and
Rescue Transponder (SART) sends a response to the radar signal. The transmitter
signal of response is 12-sweeps signal between 9,500 MHz to 9,200 MHz. The time
of slow sweep signal is 7.5
μ
s and the time of fast sweep signal is 0.4
μ
s. When the
radar receives this SART signal, a line of 12 dots appears. When the position of SART
is distant, the radar display shows only slow sweep signals like the illustration of
screen A.
When the radar reaches the SART within approximately 1 nm, the radar display can
also show the 12 responses of fast sweep signals like the illustration of screen B. The
position of the SART is the closest position of the radar echoes.
Wharf and
its echo
Large ship
Shadow sector
occurs because
wharf is hidden
behind ship.
Size of blind sector depends
on size of obstruction and range.
Radar position
Radar position
Wharf and its echo
Shadow sector occurs
because obstruction
(like mast) is in path
of radar beam.
Radar antenna
beamwidth
Screen A: When SART is distant
Screen B: When SART is close
Echo from SART
Position of
SART
Your ship
position
Your ship
position
SART mark
length
24 NM
1.5 NM
Position of
SART
Echo from
SART
Lines of 12 dots are displayed in
concentric arcs.