OVERVIEW:  The RSNA-75M aka SA-75M Dvina aka FAN SONG B radar is a trailer-mounted illumination radar for the SA-2D and SA-2F GUIDELINE SAM.  It operates in the NATO E/F- band (IEEE S-Band).

DETAILS:  The FAN SONG illumination radar systems is associated with the SA-2-series SAM.  The SNR-75 family of radars employ a complex antenna arrangement which is employed to provide range and angle tracking of the intended target, as well as the transponder beacon in the SA-2 missile, which is flown to a collision with the target using a command uplink embedded in the SNR-75 radar.

The antenna system consists of two pairs of antennas: A pair of electromechanically scanning (aka "Lewis-scanner") antennas provided vertical and horizontal target search, usually conducted in conjunction with the battery's P-12 SPOON REST radar.  This arrangement was made necessary because to the narrow, 10° × 2°  surveillance beams of the FAN SONG radar could only be steered through a 10° arc.   These perpendicularly mounted antennas created a cross-shaped beam that was centered on the target to determine its height and azimuth. These beams perform a 'flapping' motion as they scan their sectors. The FAN SONG radar had a dead zone at low altitude, which, unless covered by AAA, allowed attacking aircraft a potential avenue of attack. 

A UHF (0.3-1.0 GHz) parabolic antenna mounted on the right side of the array transmitted command signals to the missile, guiding it to the target.  

The FAN SONG is capable of engaging a single target, and had two missile uplink channels.  Deploy/Stow time was approximately 60 minutes.  The missile must pass through the guidance beam within seconds of launch in order for it to be acquired and steered to its target.

Specifications:

	Frequency:	2.965-2.990; 3.025-3.050 GHz (High E, Low F-band (NATO))
	PRF:		1100-1250; 2200-2500 pps (est)
	Power: 		 600 kW (peak)
	Range:		32,64 nm (instrumented); 
	Accuracy:		60, 180 m  (est)
			
NOTES:  IOC 1960



SOURCES:   Jane's Radar and Electronic Warfare Systems, "Fan Song missile control radars," 02 July 2001;  https://www.radartutorial.eu/19.kartei/11.ancient/karte030.en.html ; http://www.ausairpower.net/APA-SNR-75-Fan-Song.html; Steven J. Zaloga, "Red SAM: The SA-2 Guideline Anti Aircraft Missile" New Vanguard, pg. 41. ; Pike, John. "FAN SONG." GlobalSecurity.org. Last modified 7, 2019. https://www.globalsecurity.org/military/world/russia/fan-song.htm; NATO, "Current Soviet Electronic Equipment, Vol. C: Landbased, pg. I-C-13 (12 February 1969)


