Externally, the AGM-88 is of typical American missile body layout. It has double-delta fins squared off at the ends. The fins are made of a classified steel alloy to resist the tremendous aerodynamic forces in a high-speed maneuvering dive. The tail finlets are fixed, while the main fins are electrically gimballed and move cooperatively to affect movement. Internally the missile is divided into five parts: the dielectric nose cap section covering the spiral antenna, the seeker package section, the warhead, the guidance section (which also houses the DC battery and pylon interface), and the motor with it’s 303lbs of solid fuel.
The launcher rail is the LAU-118 which in turn mounts to the plane’s pylon.
One problem is that the HARM missile does not fit inside the F-22 Raptor’s or F-35 Lightning II’s stealth weapon bays. The F-35 can carry it externally (with a radar cross-section penalty), while as of June 2012 it doesn’t appear that the F-22 can use it at all.
The AGM-88 covers the C/D/E/F/G/H/I/J and part of K bands which would account for most of the world’s military radars in current use. The AGM-88 comes factory-delivered with many common threat radars already programmed in; others are added in the field as required. The onboard memory can store a huge number of potential targets, and squadrons operating HARM maintain a massive library of not only air defense radars but air traffic control radars, artillery radars, civilian radars, ECM jammers, and some datalink nodes; all of which can be attacked.
Compared to the AGM-45 Shrike, the HARM is on a whole different level. Shrike was limited to a single radar type which had to be selected before launch, whereas HARM is not, additionally HARM does not need to be locked on before launch. Shrike would crash if the targeted radar broke lock after being launched (North Vietnamese SA-2 "Guideline" troops learned to defeat Shrike by cycling their transmitters) whereas HARM can lose and reacquire the target an unlimited number of times. HARM is much longer-ranged, faster, and does not leave a smoke trail visible from the ground. HARM also does not temporarily blind the pilot at launch as Shrike did. The Shrike was retired in 1992.
Compared to the AGM-78 Standard ARM, the HARM has a much lesser drag penalty aboard the firing aircraft, and a greater number per plane can be carried. The Standard ARM was retired in 1984.
Compared to both, the Texas Instruments seeker was a generation ahead. It scans not only in frequency but also pulse-repetition (PRF) and other classified criteria; which means that modern frequency-hopping radars can be destroyed.
As a completely passive weapon, HARM is immune to chaff or decoys. The HARM’s warhead would likely do little structural damage, even to small frigates or corvettes, but as many sensors are commonly packed onto modern warship masts a single hit would likely knock the ship out of the battle.
The first SINKEX using HARM was off the coast of California on 24 October 1982, with the ex-USS Savage (DER-386) serving as the target. The test showed that a HARM would not sink the frigate but would have disabled it from participating in combat.