There are several different electronic jamming techniques. Among them, the ULQ-6 employs deception repeater jamming and false-target generation. Commonly referred to as digital radio frequency memory (DRFM),[5] the jammer digitizes characteristics of the threat radar, stores them, then uses those to broadcast back to the threat radar in deceptive ways. In the case of the AN/ULQ-6, the received signal was amplified, when transmitted back to the threat radar, to a power density equivalent to that of a capital ship like an aircraft carrier.[6] In this way, the smaller ship with the ULQ-6 repeating jammer would appear to the threat radar as a much larger target ship.[6]
Typically, two ULQ-6 systems were employed on a ship at opposing sides, 180° from each other. The combined antennas of the two provided doughnut shaped patterns covering a 360° azimuth around the ship.[6] The antenna section of each system had fixed donut-shaped upper and lower elements, with a trainable array element between them. This allowed the creation of a scannable beam in addition to a full-circle interference beam. Initially, it was only capable of operating in the 7–11GHz (4.28–2.73cm)[6] range (I-band), but later was expanded to cover the 4–8GHz (7.49–3.75cm) range (G and H-bands).[5][a]
Each AN/ULQ-6 was paired with the AN/WLR-1 electronic support measuresradar warning receiver, widely deployed in the fleet at the time. The combination ULQ-6/WLR-1 sampled incoming signals at a rate of 4 Mbps, representing amplitude characteristics by 4 bits, resulting in an instantaneous bandwidth of 10–550 MHz across an expanded operational spectrum of 2–18GHz (14.99–1.67cm).[5]
History
Adapted in 1959 from the AN/ALQ-32 airborne ECM system, the ULQ-6 for ships was envisioned as a countermeasure against Sovietanti-ship missiles like the SS-N-2 Styx or the AS-1 Kennel.[7][5] Originally operating at frequencies from 8–10GHz (3.75–3.00cm), the jamming system eventually covered from 4–10GHz (7.49–3.00cm) in all.[5] The system remained an integral part of fleet ECM through the 1970s, and was teamed up with the AN/WLR-1 electronic support measuresradar warning receiver.[5]
The system was improved over time, available in three versions:[5]
AN/ULQ-6A — The first model having a peak transmit power of 1 kilowatt with the ability to create false targets, and functioned as a track breaker.
AN/ULQ-6B — Late 1960s saw an improved version, featuring range gate pull-off (RGPO) functionality causing range errors to threat radars, and an increased peak transmit power of 25 kW (average 1 kW).
AN/ULQ-6C — An improved model with a narrower transmission beam, provided to aircraft carriers and other capital ships, to make them appear to be smaller less appealing targets.
By the mid-1970s, the system was upgraded to the AN/SLQ-30, adding a channelized SLR-12 receiver and a spinning direction finding antenna to the ULQ-6B and ULQ-6C systems.[5] However, it was thought that outdated systems such as this were becoming increasingly difficult to counter the growing threat of modern anti-ship missiles. In May 1977, an order was placed for the development of the Raytheon AN/SLQ-32, a modular, commonly designed radio detection and jamming system, which began service in 1979. Many of the ships equipped with the ULQ-6 jammer were gradually converted to the SLQ-32.[5]
By 1990, the Government Accounting Office reported US$38(equivalent to $91.46 in 2024) million worth of ULQ-6 assets were stored in Navy supply systems after removal from the fleet.[8] Installed in the early 1990s, aboard the Royal Canadian Navy's Iroquois-classdestroyers, the ULQ-6 were replaced in 1999 by Shield and Nulka decoy systems.[9]
↑Analysis 2 - The Market for Surface Electronic Warfare Systems - Archived 2/98. Forecast International.com (Report). February 1997. p.6. Retrieved November 17, 2025. In the late 1950s, the US Navy received the ULQ-6 false target generator to protect against missile attack. The design and operational doctrine of these systems was weak; they were difficult to use and were of limited effectiveness. In fact, their use was considered by many commanders to increase the chance of attack.
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