Electronic Warfare

P-35/P-37 Bar Lock radar

Also known as
  • 1RL110 P-35 Saturn
  • P-35 Saturn
  • P-35 radar
  • 1RL139 P-37 Mech
  • P-37 Mech
  • P-37 Metch
  • P-37 radar
  • Bar Lock
  • Bar Lock radar
  • 1RL139
  • 1RL110

The P-35/P-37 Bar Lock family is a Soviet transportable two-coordinate radar line used for air surveillance, fighter guidance, and target assignment to air-defense missile systems. The family links the 1RL110 P-35 Saturn and later 1RL139 P-37 Mech designations, with documented use from North Vietnam's air-defense network, Syria's T4 airbase, and Iraq's 1991 IADS to Russian and Ukrainian radar losses or targeting in the 2014 Russia-Ukraine War; open air-defense references also place P-35M/Bar Lock search radar in S-200/SA-5 site architecture.

P-35/P-37 Bar Lock radar, Transportable 2D air-surveillance and GCI radar, Electronic Warfare
Image source: Commons Soviet P-37 radar system

Role in Conflicts

Profile / Specs

Profile

Origin
Soviet Union
Built by
Soviet
Type
Transportable 2D air-surveillance and GCI radar
Service note
Introduced in the late 1950s and 1960s; later P-37 variants and modernized sets remained in post-Cold-War service.
Designer
All-Union Scientific Research Institute of Radio Engineering (VNIIRT) design lineage; Soviet production attribution retained where open sources differ on exact plant responsibility
Designed
1950s P-35 development; P-37 entered service in the early 1960s
Produced
Late 1950s onward

Specifications

Radar class
Transportable 2D air-surveillance and ground-controlled-intercept radar
NATO reporting name
Bar Lock
P-35 designation
1RL110 P-35 Saturn
P-37 designation
1RL139 P-37 Mech / Metch
Operating band
Centimeter/S-band family; GlobalSecurity lists P-35/37 carrier frequencies at 2700-3100 MHz, while Radartutorial lists P-37 fixed frequencies in the 2695-3115 MHz sub-band and Air Power Australia summarizes P-37 as 2.9-3.3 GHz
Instrumented range
About 450 km displayed range for P-37 in Radartutorial/Air Power Australia tables; other P-37 characteristic tables list 350 km maximum range
PRF
375 / 750 pulses per second for P-37
Pulse duration
1.2 microseconds for P-37
Peak power
Five transmitters at about 700 kW each for P-37
Antenna rotation
3 or 6 rpm for P-37
Range resolution
180 m in Radartutorial/Air Power Australia P-37 table
Height data
P-37 is a two-coordinate radar; Radartutorial states it could be coupled with PRV/PRW-11 or PRV/PRW-13 height-finder radars to measure the third spatial coordinate
Associated SAM site role
CSIS and FAS describe P-35M/P-35/37 Bar Lock as a target-search or acquisition radar associated with S-200/SA-5 sites
Crew
Eight-person crew listed in GlobalSecurity P-35/37 table
Deployment time
About 12 hours for a trained crew in GlobalSecurity P-35/37 table
Radar Family Notes

The Bar Lock family sits between early-warning radar and air-defense command support. P-37 was a two-coordinate circular-search radar, so a full three-coordinate air picture normally depended on a height-finder. Radartutorial identifies PRV/PRW-11 and PRV/PRW-13 as compatible height-finder radars for third-coordinate measurement, while GlobalSecurity describes Bar Lock as especially useful when collocated with Side Net-type height finders in GCI site use.

Primary role

Wide-area air surveillance, fighter guidance, and target assignment for air-defense missile systems.

Radar coordinate class

Two-coordinate search radar; height-finder coupling provided the third spatial coordinate for GCI and air-defense site use.

Site integration

Open references describe Bar Lock as especially useful when collocated with Side Net-type height finders and list P-35M/P-35/37 as a search or acquisition radar associated with S-200/SA-5 sites.

Modernization pattern

Later service-life programs focused on digital signal processing, reliability, diagnostics, secondary-radar integration, and operator-workstation improvements.

Variants

Open references usually treat P-35 Saturn and P-37 Mech as successive members of the Soviet Bar Lock 2D radar family rather than unrelated systems.

VariantConfigurationDesignation notes
P-35 Saturn1RL110 early Bar Lock model

P-35 was the earlier Soviet 2D radar in the family, accepted after state trials in 1958 and associated with the Saturn name.

Sources: P-35 radar

P-35MImproved P-35 model

The P-35M retained the recognizable stacked-feed antenna arrangement and appears in open imagery from Latvia.

Sources: Commons P-35M radar in Latvia

P-37 Mech1RL139 later Bar Lock model

Radartutorial identifies P-37 Mech as a transportable 2D radar for air surveillance, fighter guidance, and target assignment, with optional height-finder coupling for third-coordinate measurement.

Sources: Radartutorial P-37 Bar Lock

Modernized Hungarian P-37Post-Cold-War upgrade

HM Arzenal describes a Hungarian P-37 modernization program begun in 1997 that added digital signal processing, diagnostics, secondary-radar integration, operator-workstation improvements, and limited height-finding capability from five receiver channels.

Sources: HM Arzenal P-37 modernization

Air-Defense Network Links

The Bar Lock family was normally useful as part of a wider air-defense command network rather than as a standalone weapon effect.

Compatible itemItem typeCompatibility evidence
S-75 Dvina / SA-2 Guideline, High-altitude surface-to-air missile system, Air DefenseS-75 Dvina / SA-2 GuidelineHigh-altitude surface-to-air missile system

North Vietnamese SAM-regiment headquarters used Bar Lock/P-35 radar for early warning and handoff to SA-2 missile battalions, linking the surveillance radar to S-75/SA-2 engagements against U.S. aircraft.

Sources: Wild Weasels SA-2 and SR-71, USAF Air War North Vietnam 1965-1968, CIA North Vietnamese Antiaircraft Defense System

S-200 / SA-5 Gammon, Long-range surface-to-air missile system, Air DefenseS-200 / SA-5 GammonLong-range surface-to-air missile system

S-200 battery command-post documentation describes integration of track data from acquisition radars such as P-35/37 Bar Lock; CSIS and FAS also place P-35M/P-35/37 Bar Lock search or acquisition radar in S-200/SA-5 site architecture.

Sources: Air Power Australia Engagement and Fire Control Radars, CSIS S-200 Missile Threat, FAS S-200 SA-5 Gammon

S-125 Neva/Pechora / SA-3 Goa, Short- to medium-range surface-to-air missile system, Air DefenseS-125 Neva/Pechora / SA-3 GoaShort- to medium-range surface-to-air missile system

Bellingcat's T4 airbase analysis identified two P-35/37 Bar Lock radars directing active S-75 and S-125 SAM sites during the Syrian Civil War.

Sources: Bellingcat Fortress T4

Height and command context

The P-37 remained a two-coordinate radar, so height-finder and command-post integration shaped how Bar Lock data could be used for fighter guidance, SA-2 handoff, or SA-5 target acquisition.

Sources: Radartutorial P-37 Bar Lock, GlobalSecurity P-35/37 Bar Lock, Air Power Australia Engagement and Fire Control Radars, FAS S-200 SA-5 Gammon

Timeline

P-35/P-37 Bar Lock radar Key Events

  1. P-35 Saturn accepted into service

    Open references place the P-35 Saturn's state-trial completion and Soviet service acceptance in 1958.

    Sources: P-35 radar

  2. P-37 Mech enters service

    Radartutorial identifies P-37 Mech as entering service in 1961 as a transportable Bar Lock 2D radar.

    Sources: Radartutorial P-37 Bar Lock

  3. Bar Lock radars documented in North Vietnam

    U.S. Air Force historical reporting described North Vietnamese Bar Lock radars near Haiphong and in western Route Package 5, contributing to early-warning and GCI coverage.

    Sources: USAF Air War North Vietnam 1965-1968, Wild Weasels SA-2 and SR-71

  4. Iraq employs Bar Lock radars in its IADS

    Air Power Australia describes Iraqi P-35M and P-37 Bar Lock radars as top-tier GCI and early-warning sensors in Iraq's integrated air-defense system during Operation Desert Storm.

    Sources: Air Power Australia Desert Storm EW

  5. Hungarian P-37 modernization begins

    HM Arzenal states that Hungary's P-37 modernization program started in 1997, with the first modernized radar handed over in 1999.

    Sources: HM Arzenal P-37 modernization

  6. P-37 Mech reported destroyed in occupied Crimea

    Ukrainian reporting attributed a strike at Kirovske airfield to Ukraine's Unmanned Systems Forces and Defence Intelligence, described the use of FP-2 attack drones, and identified a Russian P-37 Mech radar among the destroyed targets.

    Sources: Ukrainska Pravda Kirovske strike, UNN Kirovske P-37 report, NV Kirovske P-37 report, Defense Express Kirovske P-37 report

Media

P-35/P-37 Bar Lock radar Videos

P-35/P-37 Bar Lock radar Images

P-35/P-37 Bar Lock radar, Transportable 2D air-surveillance and GCI radar, Electronic Warfare - view 1
Source: Commons P-35M radar in Latvia
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Sources

P-35 radarPublisher: Wikipedia | Note: Starting reference for P-35 Saturn identity, 1RL110 designation, 1958 service acceptance, Bar Lock naming, and broad family relationship to P-37. | Accessed: 2026-07-01Radartutorial P-37 Bar LockPublisher: Radartutorial | Note: Supports P-37 Mech identity, 1RL139 designation, transportable 2D radar role, height-finder coupling, service-entry context, and P-37 technical characteristics. | Accessed: 2026-07-01Air Power Australia Bar Lock reportPublisher: Air Power Australia | Note: Supports the Bar Lock family grouping and P-37 specification table, including operating band, PRF, pulse duration, displayed range, range resolution, sweep rate, and LEMZ characteristic table values. | Accessed: 2026-07-01GlobalSecurity P-35/37 Bar LockPublisher: GlobalSecurity.org | Note: Supports P-35/37 Bar Lock background, circular-search role, wide GCI use, height-finder collocation context, crew count, deployment-time table value, and selected technical characteristics. | Accessed: 2026-07-01HM Arzenal P-37 modernizationPublisher: HM Arzenal | Note: Supports Hungarian P-37 modernization history and upgrade details for transmitter, receiver, signal-processing, diagnostics, secondary-radar integration, and operator-workstation changes. | Accessed: 2026-07-01Radartutorial PRV-11 Side NetPublisher: Radartutorial | Note: Supports PRV/PRW-11 height-finder context, including its radio-altimeter role and use after target assignment by a panoramic surveillance radar or automated guidance system. | Accessed: 2026-07-01Radartutorial PRV-13 Odd PairPublisher: Radartutorial | Note: Supports PRV/PRW-13 height-finder context for the Bar Lock family section, including its Warsaw Pact height-finder role and remote-control description. | Accessed: 2026-07-01CSIS S-200 Missile ThreatPublisher: Center for Strategic and International Studies Missile Threat | Note: Supports the relationship between S-200/SA-5 batteries and P-35M target-search and acquisition radar in typical S-200 site architecture. | Accessed: 2026-07-02Air Power Australia Engagement and Fire Control RadarsPublisher: Air Power Australia | Note: Supports S-200/Square Pair command-post context, including integration of track data from acquisition radars such as P-35/37 Bar Lock and supporting height-finders. | Accessed: 2026-07-02FAS S-200 SA-5 GammonPublisher: Federation of American Scientists | Note: Supports the P-35/37 Bar Lock association with SA-5 sites and lists P-35M Bar Lock-B as target-search and acquisition radar in an S-200 battalion. | Accessed: 2026-07-02Commons P-35M radar in LatviaPublisher: Wikimedia Commons | Note: Supports image provenance for the P-35M radar photograph retained in the gallery; the file page identifies the subject and CC BY 3.0 licensing metadata. | Accessed: 2026-07-01Commons Soviet P-37 radar systemPublisher: Wikimedia Commons | Note: Supports image provenance for the P-37 Bar Lock photograph used as the primary image; the file page identifies U.S. Defense Imagery provenance and public-domain U.S. military licensing metadata. | Accessed: 2026-07-01Bellingcat Fortress T4Publisher: Bellingcat | Note: Supports direct 2011 Syrian Civil War use context by documenting two P-35/37 Bar Lock radars at Syrian government T4 airbase directing active S-75 and S-125 SAM sites and detecting aircraft over central Syria. | Accessed: 2026-07-02Ukrainska Pravda Kirovske strikePublisher: Ukrainska Pravda | Note: Supports direct 2014 Russia-Ukraine War use context by reporting that Ukrainian Unmanned Systems Forces and Defence Intelligence destroyed a Russian-occupied Crimea target set including a P-37 Mech radar at Kirovske airfield. | Accessed: 2026-07-01Oryx Russian equipment lossesPublisher: Oryx | Note: Supports direct 2014 Russia-Ukraine War use context by listing a visually documented Russian 1RL110 P-35 Saturn or 1RL139 P-37 Mech radar destroyed during the Russian invasion of Ukraine. | Accessed: 2026-07-01Oryx Lancet miss listPublisher: Oryx | Note: Supports direct 2014 Russia-Ukraine War use context by listing a Ukrainian P-35/37 Bar Lock radar among Ukrainian equipment missed by a Russian Lancet-3 loitering munition. | Accessed: 2026-07-01WarSpotting Kirovske P-35 P-37 lossPublisher: WarSpotting | Note: Supports direct 2014 Russia-Ukraine War use context by recording a Russian 1RL110 P-35 Saturn or 1RL139 P-37 Mech loss at Kirovske airbase on 2 April 2026. | Accessed: 2026-07-01UNN Kirovske P-37 reportPublisher: Ukrainian National News | Note: Supports direct 2014 Russia-Ukraine War use context by reporting the 2 April 2026 Kirovske airfield strike and identifying a P-37 Mech circular-surveillance radar station on the Russian side among the hit targets. | Accessed: 2026-07-01NV Kirovske P-37 reportPublisher: The New Voice of Ukraine | Note: Supports direct 2014 Russia-Ukraine War use context by reporting that Ukrainian forces destroyed a Russian P-37 Mech radar at Kirovske airfield in occupied Crimea with FP-2 drones. | Accessed: 2026-07-01Defense Express Kirovske P-37 reportPublisher: Defense Express | Note: Supports direct 2014 Russia-Ukraine War use context by reporting that Ukraine's Unmanned Systems Forces and Defence Intelligence destroyed a Russian P-37 Mech radar during the Kirovske airfield strike. | Accessed: 2026-07-01Air Power Australia Desert Storm EWPublisher: Air Power Australia | Note: Supports direct 1990 Gulf War use context by describing Iraqi P-35M and P-37 Bar Lock radars in Iraq's integrated air-defense system for wide-area surveillance, early warning, fighter GCI support, and warning handoff to SAM and AAA batteries. | Accessed: 2026-07-01War on the Rocks Iraqi Bar LockPublisher: War on the Rocks | Note: Supports direct 1990 Gulf War use context by identifying Soviet-supplied P-35/37 Bar Lock radars as part of Iraq's early-warning network during Desert Storm. | Accessed: 2026-07-01Wild Weasels SA-2 and SR-71Publisher: Wild Weasels | Note: Supports direct 1955 Vietnam War use context by describing North Vietnamese SAM regiment headquarters using Bar Lock/P-35 radar for aircraft early warning and handoff to SA-2 missile battalions. | Accessed: 2026-07-01CIA North Vietnamese Antiaircraft Defense SystemPublisher: Central Intelligence Agency Reading Room | Note: Supports direct 1955 Vietnam War use context by identifying P-35 Bar Lock radar in North Vietnamese antiaircraft-defense equipment and deployment reporting. | Accessed: 2026-07-02USAF Air War North Vietnam 1965-1968Publisher: Office of Air Force History | Note: Supports direct 1955 Vietnam War use context by documenting North Vietnamese Bar Lock radars in the GCI and early-warning network and U.S. efforts to jam or attack that radar capability. | Accessed: 2026-07-01