DER Conversion Details

Radar Picket Ship Conversion (DER)

This port quarter down view of the USS Otterstetter (DER-244) was taken on 12 May 1952. She is carrying two of the new rapid-fire radar controlled 3" guns, one forward and one aft. In place of her number two gun she mounts the Mark 15 trainable hedgehog. All 20mm, 40mm AA guns and K-guns have been grounded, although one depth charge rack remains at the stern.
National Archives #80-G-443668.

    By 1945 the Japanese were using Kamikaze suicide planes against our ships. The Germans had also perfected the FX-1400 "Fritz" the bomber-launched radio guided bomb, which had been used successfully against the USS Savannah (CL42) and the Italian battleship Roma in the Mediterranean in 1943. Further, advances in technology were producing much faster aircraft, which reduced warning time. Compounding the effectiveness of the Kamikazes, the Japanese had developed highly successful attack tactics; formations of high-flying Kamikazes flew into the radar "void" directly above the ships and dove straight down into the ships, thus reducing much of the tracking radar's and AA's effectiveness.
    In an effort to provide the fleet with more advance warning of these Kamikazes, the navy converted DEs into radar-equipped pickets (DER). The DERs provided advance warning of air attacks, jammed enemy radar and communications frequencies, and vectored friendly aircraft into attack positions. In addition to all the electronic gear upgrades, the DERs received significant weapons upgrades. Two 5"/38s replaced the numbers one and three 3" guns. A Mk1 twin 40mm replaced the number two 3", and two Mk 1s replaced the triple torpedo launcher. Finally, a Mk 2 quad 40mm was installed into the X-position. All single barrel 20mm guns were replaced with four Mk 24 twin 20mm mounts, two on each side of the bridge. As an anti-aircraft ship, the hedgehog and K-guns were removed, but the depth charge racks remained.
    The radar enhancements included an SL, SA, SU or SP surface and air search radar dish, an IFF, DBM radar direction finder, a TDY jamming array, and a YF aircraft homing beacon. Details of these antennas can be found in the electronic page.