The USR-23 is an active tracking receiver, and is typically used along with a hydrophone and a pair of headphones in order to locate and identify targets while on a boat or pier or any other location that provides access to water of at least 1 meter in depth. Additionally, the integral display of the USR-23 provides ID information from ACT and Rcode transmitters, as well as decoded data from telemetry tags such as pressure or temperature, and may record these detections in its internal non-volatile memory for later retrieval. Furthermore, the rugged construction of the USR-23 and internal NiCd batteries allow operation in remote areas, away from normal power sources.
OPERATION
When operated with a directional hydrophone, the USR-23 is first preset to a particular operating frequency, then rotating the hydrophone through 360º while listening for pings with attached headphones, and repeating this procedure for each frequency of interest. The USR-23 may also be set to scan pre-selected frequencies, significantly reducing the labor involved in tracking tags utilizing multiple frequencies.
DETECTION
When a received signal from a transmitter is of sufficient strength and duration, it is “detected” by the USR-23. The time interval between successive detections is analyzed, and pertinent data is displayed on the bottom line of the LCD. By careful use of the GAIN control of the USR-23, it is possible to both obtain telemetry information from sensing tags at long ranges, or separate signals from multiple tags transmitting on the same frequency. The GAIN setting varies how much an input signal is amplified: for tags at far distance from the receiver, the GAIN may be increased to achieve maximum amplification. Conversely, when a transmitter is very close to the receiver, or multiple tags are heard in the headphones, reducing GAIN will produce a more pleasant tone, and allow discrimination of several tags. At very close ranges, reducing the gain also increases the apparent directivity of a directional hydrophone, making locating of a target easier. In addition, in very noisy environments, detections may be increased by using a lower gain setting, thereby limiting the amount of distraction.
