Specifications

BATS AND PORTABLE BATS OPERATION
3-62
Interrogation Interval for a transponder should not be less than 2 seconds; most transponders
have a 1.5- to 1.75-second lock-out time built in to prevent interrogation echoes from retriggering
the transponder. If interrogating two transponders at different frequencies then it’s possible to de-
crease the Interrogation Interval to less than two seconds as the Interrogation Interval for a single
target is the total of the intervals. E.g., interrogate #1 at 17kHz every 1.5 seconds and #2 at
19kHz every 1.5 seconds, the sequence interval for the two targets is 3.0s which is still greater
than the lockout time of the transponders. Also keep in mind that when using telemetering tran-
sponders the second (telemetry) reply may come in up to one second later than the primary (navi-
gation) reply. Increase Interrogation Interval accordingly.)
NOTE: With EdgeTech Model 4370 series of transponders, pulse widths of less than 5 msec
may not properly interrogate the transponder.
At a XMIT INTERVAL of 2 seconds, a transponder turnaround time of 15 ms and a speed of sound
input of 1500 meters/second the maximum range the system could track the transponder would be
about 1400 meters. [(1500m/s * (2s - .015s)) / 2 = 1489 m] If a telemetry transponder were used
at its maximum range (telemetry delay of 1 second from primary reply) then the maximum range
would be reduced further to about 700 meters. [(1500m/s * (2s - 1s - .015s)) / 2 = 738.75m]
Input Speed Of Sound
The correct speed of sound in the water column between the transponder and the hydrophone
must be entered for accurate tracking in the transponder mode. From the Project Tree select
“Acoustic data”. Input the sound speed in meters per second or feet per second or yards per se-
cond, depending on the current unit of measure.
The speed of sound in the water column is used to determine the transponder range. The average
water column temperature is usually different than near-surface temperature (the temperature
measured by the hydrophone), and therefore, this speed of sound generally differs from that com-
puted by the operator from a reading of the hydrophone temperature. (The hydrophone tempera-
ture is used only to determine the target depression angle correction.)
If the Sound Velocity Profile is known it can either be entered manually or imported from the file.
Check the SV Profile box and click on the “SV Profile Setup” button.
Target Depth
The target depth parameter can either be manually entered, telemetered or input via analog-in
Depth BNC. Choose the method used to update the depth parameter.
The system is now tracking in the transponder mode, and you should observe the following:
 Target position displayed in the tracking window, represented by the target designated as the
transponder.
 The chosen target symbol shown in the status block with position data agreeing with the target
position on the grid.