Air Defense

76N6 Clam Shell

Also known as
  • 76N6 low-altitude detector
  • 76N6 low-altitude acquisition radar
  • Clam Shell
  • 5N66
  • 5N66M
  • 76N6E
  • 76N6S
  • LAD
  • Nizkovysotniy Obnaruzhitel

The 76N6 Clam Shell is a Soviet/Russian S-300-family low-altitude acquisition radar built to find small, low-flying targets such as cruise missiles and terrain-following aircraft. It supplements the S-300 battery's wider search and fire-control radars by improving coverage near the radar horizon, often from a 40V6M or 40V6MD mast. Direct Ukraine-war evidence identifies Clam Shell-family equipment in Slovakia's S-300PMU transfer to Ukraine and a 76N6 radar destroyed with Russian S-300 equipment at Voronezh in August 2025.

76N6 Clam Shell, S-300-family low-altitude acquisition radar, Air Defense
Image source: Wikimedia 76N6 Clam Shell Image

Role in Conflicts

Profile / Specs

Profile

Origin
Soviet Union / Russia
Built by
Almaz-Antey
Type
S-300-family low-altitude acquisition radar
Service note
Cold War S-300P-family radar line still documented with S-300 batteries in the 2020s
Designer
Lianozovo Electromechanical Plant (LEMZ) / S-300P radar-industrial lineage
Produced
Marketed with S-300PMU-era equipment by LEMZ in the 1990s; associated 5N66/5N66M/76N6 designations remain in S-300-family references

Specifications

Radar role
Low-altitude acquisition and target-designation radar for S-300/SA-10 battery fire-control systems
NATO reporting name
Clam Shell
Associated designations
5N66, 5N66M, 76N6, 76N6E, and 76N6S in open references
Transmission type
Frequency-modulated continuous-wave radar in Air Power Australia and Military Periscope descriptions
Primary target set
Low-flying aircraft, cruise missiles, terrain-following aircraft, and other low-radar-cross-section targets in clutter
Frequency band
S band in the LEMZ specification table reproduced by Air Power Australia; some open S-300 radar tables classify Clam Shell in NATO I-band terms
Detection range
Air Power Australia's LEMZ table gives radar-horizon-limited performance at extremely low altitude, 90 km at 500 m altitude, and 120 km at 1,000 m altitude
Tracked targets
180 targets in the LEMZ specification table reproduced by Air Power Australia
Data output rate
3 seconds in the LEMZ specification table
Antenna rotation
20 rpm in the LEMZ specification table
Power
55 kW maximum power consumption and at least 1.4 kW average CW transmit power in the LEMZ specification table
Mast options
40V6M and 40V6MD elevated mast configurations; Euro-SD describes approximate antenna-head heights around 24 m and 38 m
Deployment time
Air Power Australia's LEMZ table lists 1 hour to deploy on a 40V6M mast and a 2.5 minute warmup time
Associated systems
S-300P, S-300PT/PS, S-300PMU, and related SA-10/S-300-family batteries
Low-Altitude Search Role

The Clam Shell fills the low-altitude search layer in an S-300 battery. It is described as a frequency-modulated continuous-wave acquisition radar intended to detect low-radar-cross-section targets in clutter and electronic-countermeasure conditions, then provide target-track information to the fire-control system.

Sensor function

Low-altitude acquisition and target designation for S-300/SA-10 fire-control elements.

Low-altitude problem

Mast mounting helps push the radar horizon outward for aircraft, drones, cruise missiles, and terrain-following targets flying close to the ground.

Battery fit

The radar supplements, rather than replaces, the S-300 battery's long-range search radar and 30N6-family engagement radar.

Mobility cost

Euro-SD notes that mast-mounted radars can improve low-altitude coverage but add setup and takedown time, which matters for survivability.

Source references: Air Power Australia 76N6 Clam Shell; GlobalSecurity 76N6 Clam Shell; Military Periscope 76N6 Clam Shell; Euro-SD Long-range SAMs.

Variants

Open sources use several related designations for the Clam Shell low-altitude detector. The 5N66/5N66M and 76N6/76N6E names appear around S-300P, S-300PT/PS, and S-300PMU-family radar sets rather than as separate standalone weapons.

VariantConfigurationDesignation notes
5N66 / 5N66MEarly Clam Shell low-altitude detector designations

Air Power Australia groups 5N66 and 5N66M with the 76N6/76N6E Clam Shell family; Oryx separately identifies a Slovak 5N66M Clam Shell delivered for S-300PMU use.

Sources: Air Power Australia 76N6 Clam Shell, Oryx Slovak Arms Deliveries to Ukraine

76N6 / 76N6ES-300PMU-family low-altitude acquisition radar

The LEMZ-backed technical summary treats 76N6/76N6E as Clam Shell family radars used to feed low-altitude target tracks to SA-10/S-300 fire-control elements.

Sources: Air Power Australia 76N6 Clam Shell, Military Periscope 76N6 Clam Shell

76N6 on 40V6M/40V6MD mastElevated low-altitude coverage configuration

Air Power Australia and Euro-SD describe the radar mounted on 40V6M/40V6MD mast systems to improve coverage of low-altitude targets near the radar horizon.

Sources: Air Power Australia 76N6 Clam Shell, Euro-SD Long-range SAMs

Air-Defense Systems

The 76N6 is a battery sensor rather than a standalone launcher; its catalog value comes from how it extends S-300-family low-altitude search coverage.

Compatible itemItem typeCompatibility evidence
S-300, Long-range surface-to-air missile system, Air DefenseS-300Parent SAM family

Specialist and open-source references describe the Clam Shell as an S-300/SA-10 acquisition radar used with S-300P, S-300PMU, and related battery configurations.

Sources: Air Power Australia 76N6 Clam Shell, GlobalSecurity 76N6 Clam Shell

30N6 engagement radar, S-300-family engagement and missile-guidance radar, Air Defense30N6 engagement radarEngagement radar partner

The 76N6 feeds low-altitude target information into the S-300 engagement chain, complementing the 30N6 Flap Lid or Tomb Stone fire-control radar rather than replacing it.

Sources: Air Power Australia 76N6 Clam Shell, Wikimedia 76N6 and 30N6 Image

Component record scope

Conflict rows here are limited to sources that identify Clam Shell, 5N66M, or 76N6 radar equipment directly; broader S-300 missile and launcher use remains on the parent S-300 page.

Sources: Oryx Slovak Arms Deliveries to Ukraine, Ukrainska Pravda Voronezh S-300 Radars

Timeline

76N6 Clam Shell Key Events

  1. LEMZ brochure becomes an open reference point

    Air Power Australia's 76N6 technical report cites a 1994 Lianozovo Electromechanical Plant brochure for Clam Shell specifications and S-300PMU-family context.

    Sources: Air Power Australia 76N6 Clam Shell

  2. Slovak S-300PMU radar set reaches Ukraine

    Oryx lists Slovakia's S-300PMU-related radar deliveries to Ukraine as including one 5N66M Clam Shell, one 5N63S Flap Lid B, and one 36D6 Tin Shield.

    Sources: Oryx Slovak Arms Deliveries to Ukraine

  3. 76N6 reported destroyed at Voronezh

    Ukrainska Pravda, citing CyberBoroshno analysis, reported that a Russian S-300 radar set struck at the 108th Anti-Aircraft Missile Regiment and Baltimore airfield included 76N6 and 30N6 radars.

    Sources: Ukrainska Pravda Voronezh S-300 Radars

Media

76N6 Clam Shell Videos

76N6 Clam Shell Images

76N6 Clam Shell, S-300-family low-altitude acquisition radar, Air Defense - view 1
Source: Wikimedia 76N6 and 30N6 Image
76N6 Clam Shell, S-300-family low-altitude acquisition radar, Air Defense - view 2
Source: Wikimedia 76N6 Clam Shell Image 6
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Sources

Air Power Australia 76N6 Clam ShellPublisher: Air Power Australia | Note: Supports 76N6/5N66M Clam Shell identity, LEMZ brochure context, S-300/SA-10 relationship, low-altitude FMCW search role, mast use, and the listed specifications. | Accessed: 2026-07-02GlobalSecurity 76N6 Clam ShellPublisher: GlobalSecurity.org | Note: Supports 76N6/76N6S identity, S-300PMU battery relationship, automatic low-altitude target-search role, and target-designation function for the S-300 complex. | Accessed: 2026-07-02Military Periscope 76N6 Clam ShellPublisher: Military Periscope | Note: Supports country of origin, ground-radar identity, frequency-modulated continuous-wave target-acquisition role, dense-ECM framing, and low-RCS target focus. | Accessed: 2026-07-02Euro-SD Long-range SAMsPublisher: European Security & Defence | Note: Supports the 76N6 relationship to S-300, 40V6M/40V6MD mast use, approximate mast heights, radar-horizon context, and setup/takedown tradeoff for mast-mounted air-defense radars. | Accessed: 2026-07-02Oryx Slovak Arms Deliveries to UkrainePublisher: Oryx | Note: Supports 2014 Russia-Ukraine War direct transferred to Ukraine context for a Slovak 5N66M Clam Shell radar delivered with S-300PMU-related radar equipment. | Accessed: 2026-07-02Ukrainska Pravda Voronezh S-300 RadarsPublisher: Ukrainska Pravda | Note: Supports 2014 Russia-Ukraine War direct fielded/lost by Russia context for a 76N6 radar identified with Russian S-300 equipment hit at the 108th Anti-Aircraft Missile Regiment and Baltimore airfield in Voronezh in August 2025. | Accessed: 2026-07-02Wikimedia 76N6 Clam Shell ImagePublisher: Wikimedia Commons | Note: Image provenance and license page for the primary 76N6 Clam Shell acquisition radar image, photographed by ShinePhantom and published under Creative Commons Attribution-ShareAlike 3.0. | Accessed: 2026-07-02Wikimedia 76N6 and 30N6 ImagePublisher: Wikimedia Commons | Note: Image provenance and license page for the gallery image showing a 76N6 acquisition radar beside a 30N6 Flap Lid fire-control radar, published under Creative Commons Attribution-ShareAlike 3.0. | Accessed: 2026-07-02Wikimedia 76N6 Clam Shell Image 6Publisher: Wikimedia Commons | Note: Image provenance and license page for an additional 76N6 Clam Shell acquisition radar gallery image from the Togliatti technical museum, photographed by ShinePhantom. | Accessed: 2026-07-02