Directional Hydrophone

This unit provides the greatest range and precision in locating tags in lakes, rivers, and oceans, and permits rejection of local noise caused by dams or pumping stations in rivers and streams. The DH-4 is the primary hydrophone for both fixed stations and manual tracking.

DH-4 OPERATION: 

Typically the DH-4 is mounted to a staff (such as 1 1/4” PVC pipe) by tightening the nylon mounting screws included with the hydrophone against the outside wall of the staff.   If a pipe or other hollow staff is used, a 5/8” hole may be drilled above the hydrophone, allowing the cable to travel up the center pipe providing maximum protection against chafing or tearing of the outer insulation.  The top of the staff should be marked so that the direction the hydrophone is being pointed is apparent while the hydrophone is submerged in the water. 

Key to using the DH-4 is its  +/- 6° beam width: this provides a very accurate determination of the bearing to targeted pinger.  The hydrophone can be slowly rotated on the pole so that the entire 360° field is covered.  As the user gets closer to the pinger, the signal in the headphones will increase, and may become difficult to determine a precise direction:  reducing using the gain of the receiver will regain some directionality.  If precise location <10m is desired, attenuators (Sonotronics accessory, ATN-95) may be used to further reduce incoming signal, enhancing directionality.