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  Specialized Transducers for CHIRP SONAR

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Author Topic:   Specialized Transducers for CHIRP SONAR
jimh posted 03-23-2011 07:51 AM ET (US)   Profile for jimh   Send Email to jimh  
AIRMAR have introduced new SONAR transducers which are specially designed for use with frequency-modulated pulse-compression or chirp SONAR devices. Pulse-compression SONAR devices use continuouswave wave frequency-modulated signals to excite the transducer, and this requires that the transducer have a broad frequency response. Currently the most likely frequency-modulated or chirp SONAR unit to be used with recreational boats is the SIMRAD BDM-2 device. The AIRMAR transducers are assumed to be designed for compatibility with the BSM-2. Details of the several new transducer products are given in

http://airmartechnology.com/uploads/Brochures/BB_Transducers_BR_rC_lr. pdf

Prices for these devices appear to be in the $1,200-range. One vendor has a few models listed for sale. See:

http://www.boemarine.com/products/GCO-B265-C-LH/ airmar-b265-c-lh-1kw-chirp-broadband-transducer

jimh posted 03-23-2011 08:07 AM ET (US)     Profile for jimh  Send Email to jimh     
The technical literature from AIRMAR (linked above) also has a good explanation of how conventional monotonic SONAR transmission techniques contain a limitation on target resolution based on the length of the transmitted pulse. As the length of the transmitted pulse is increased, the ability of the SONAR to differentiate targets which are close together is reduced. A significant advantage of pulse-compression techniques is freedom from this limitation, allowing resolution of two targets which are in close proximity, such as a fish near the sea bottom or other fish.

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