SANDERS AN/ALQ-51/ -51A/ -100 DECEPTION JAMMER AND TRACK BREAKER

The AN/ALQ-51 is a deceptive track breaker to counter S-band fire control radars which employ pulse ranging, frequency modulating carrier wave pulse, and conical scan.  It is also designed to cause proximity fuses on the SA-2 SAMs to detonate prematurely or be duded so they did not detonate at all.  The AN/ALQ -51 Mod I performed the following functions:
  • Range gate pull-off
  • Frequency translation
  • Inverse conical scan deception
  • angular deception

The ALQ-51 was not particularly powerful and as a deception jammer gave a false return to the radar of the missile or gun that had it targeted.  The theory was that the confused radar operator would not be able to decipher which return was real and therefore could not figure out which target to fire at.
The AN/ALQ-51 seems to be very highly regarded in Navy circles at the time.  By the end of the conflict, it was used by almost all of their carrier-based aircraft.  At the end of his 1966 cruise aboard the USS Franklin D Roosevelt, VF-14s squadron commander recommended, “…equipment such as the ALQ-51 is urgently needed in F-4 aircraft to operate in this area of operations.”


But the Air Force was highly skeptical of its value.  They tried the AN/ALQ-51 on several of its RF-101s and RF-4s, but their feeling was that when the North Vietnamese radar operators saw the false targets they simply fired more guns and missiles and the chance of damage from this barrage of fire offset the ALQ-51s usefulness.  On August 1, 1967, the Air Force lost an RF-101C to a SAM even though it was equipped with the AN/ALQ-51.  Already suspecting that the ALQ-51 was ineffective, the Seventh Air Force withdrew it from service. But this may have been more of a question of tactics than effectiveness.  The Air Force tried it on reconnaissance aircraft which flew their missions as a single aircraft.  But EW equipment proved more effective as part of a formation providing mutual protection as the Air Force later learned with their ECM pods.  This may explain why the Navy realized more success with the equipment than the Air Force.

AN/ALQ-51A S/E/F-Band Deception Jammer and Track Breaker

Starting in February 1967 the AN/ALQ-51 Mod I systems began to be upgraded to AN/ALQ-51A Mod II standard.  The new upgrade used an automatic deception repeater against ground fire-control radars, track while scan radars, and SA-2 guidance systems.  It functioned as a track breaker against conical scan radars in the frequency range of 2-4 GHz.  Most of the conversions were completed by the fall of 1967.  The equipment was a direct replacement of the AN/ALQ-51 Mod I, and used the same antennas and fairings, so externally there were no differences.

AN/ALQ-100 E/F/G/H-Band Deception Jammer and Track-Breaker


The AN/ALQ-100 was a direct replacement upgrade of the AN/ALQ-51 system.  It was designed to provide azimuth, elevation, and range deception against fire control radars.  The AN/ALQ-100 operated in the 1.8 - 8.0 GHz band for pulse radar and 4.0 - 8.0 GHz band for continuous wave radars.  The AN/ALQ-100 would simultaneously deceive radars in one or more frequency bands or modes of operation.  It would also detonate or dud continuous wave proximity fuses in SAM, AAM, or AAA projectiles.  Externally identical to the AN/ALQ-51 / -51A installations.  F-4s were modified with this system starting in June 1967.



F-4B/N - AN/ALQ-51 /-51A /-100 AFT Cockpit Controls


F-4B/N Rear Cockpit
"Post Shoehorn"
(click picture to enlarge)
1 - F-4B/N Integrated Control Panel
(controls AN/APR-27, AN/ALE-29 & AN/ALQ-51/100)

F-4B/N - AN/ALQ-51 /-51A /-100 Antennas - Shoehorn Mods 1 & 2 Aircraft


(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Fwd Receive Antenna
2 - AN/ALQ-51 /-51A /-100 Fwd CW Transmit Antenna

(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Aft CW Transmit Antenna
2 - AN/ALQ-51 /-51A /-100 Aft Receive Antenna
(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Aft Pulse Transmit Antenna

(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Fwd Pulse Transmit Antenna

F-4B/N - AN/ALQ-51 /-51A /-100 Antennas - Shoehorn Mod 3 Aircraft


(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Fwd Receive Antenna
2 - AN/ALQ-51 /-51A /-100 Fwd CW Transmit Antenna

(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Aft CW Transmit Antenna
2 - AN/ALQ-51 /-51A /-100 Aft Receive Antenna

(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Aft Pulse Transmit Antenna

(click picture to enlarge)
1 - AN/ALQ-51 /-51A /-100 Fwd Pulse Transmit Antenna



Revisions:
  • 15 APR 2014 - Added artwork for F-4B/N rear cockpit controls
  • 26 MAR 2014 - Initial Post
Sources:

3 comments:

  1. From 1971-1974 I was a USN COM-NAV-ECM avionics tech in Attack Squadron 147, deployed aboard USS Constellation CVA-64. The AN/ALQ-100 jammers apparently worked well, as I recall no losses or significant damage to our A7E's during the 1971-72 or 1973 WESPAC deployments. On one occasion a SAM flew right between a flight of two of our A7E's in very close proximity, but kept going past and did not detonate. The pilots were not amused.

    The supposed loss of an F4J (Cunningham/Driscoll) was bogus, they ran out of fuel after a vicious dogfight with the Phantom at full military afterburner at 10,000 Ft or less..for a long time (minutes that is). Can't blame them for that!

    Perhaps due to their larher size compared to the A7's, VF-92 and VF-96 F-4's, also carrying ALQ-100s, received frequent but not fatal AAA damage.

    I was in O-level hands-on maintenance/repair throughout the very "busy" 1971-1972 ops, but I don't recall any AAA hits on our planes.

    The ALQ 100 Receiver/Transmitter units were, indeed, the heaviest avionics gear on board the A7E's and getting all the pesky interconnecting cables on properly was truly a B****, but I have always been very impressed by the system's apparent effectiveness.

    ReplyDelete
    Replies
    1. There was SAM damage on an RA5C on May 10th 1972. The SAM detonated right under the aircraft but the plane was able to continue its RECCE run. Place assigned to RVAH-11, CVA-64.

      Delete
  2. The Navy and USMC A-6 Intruder Series Attack Bombers carried two sets of AN/ALQ-100s fore and aft. They were very heavy devices. I toted a few of them around the USS Coral Sea. They were triggered by the ALR-45? which used an array of antennas to determine missile tracks and distance. That technology is about 50 years old as of 29May19. I wonder if the Growler is going to be replaced by a drone with all the newest ECM automated or remotely controlled.

    ReplyDelete

I welcome any comments, corrections, and additions to this blog. If you have corrections or additions please give references so they can be properly cited.