OVERVIEW:  The SJD-3 aka Tamir-11 aka STAG HOOF is an active, dual-frequency sonar operating in the high sonar frequency band.

DETAILS:  The SJD-3 is a Chinese copy of the Tamir-11 STAG EAR sonar.  It is a searchlight sonar, meaning it can only look in one direction at a time and must swing around to see what is in the other directions area by area. The Tamir was probably copied from UK or German WWII sonars.  Unlike most sonars, nstead of being fixed to the hull, SJD-3 has a telescoping arm, so when not in use, the sonar is stored in the hull, and when deployed, the sonar is lowered into water several meter below the hull, thus increased detection range by avoiding baffles generated by the hull.   

Specifications:
	Frequency: 	15, 24 kHz
	Range:		2.0 nm

			
NOTES:  IOC 1947  (Tamir); early 1960's (SJD-3).  Corresponding surface ship set is the Tamir-5N.


SOURCES: Friedman, The Naval Institute Guide to World Naval Weapons Systems 1997-98, pg. 607, 579 ; "At the forefront of the underwater confrontation: submarine hydroacoustics. From the beginning of the cold war to the 70s." Top War. Last modified August 7, 2020. https://en.topwar.ru/173865-na-ostrie-podvodnogo-protivostojanija-gidroakustika-podlodok-ot-nachala-holodnoj-vojny-do-70-h.html.; Chinese Frigate Siping (544)." Wikipedia, the Free Encyclopedia. Last modified March 13, 2023. https://en.wikipedia.org/wiki/Chinese_frigate_Siping_(544).


