Poison and Antidote

Israel lost another Phantom over the Suez Canal last week--the third shot down in three weeks by SA-2 missiles. Israeli technicians are certain that they know why. The new missiles were tuned to a new range of frequencies, and the electronic countermeasure (ECM) devices carried by Israeli jets to spoof or confuse attacking missiles were not capable of picking up those frequencies. The Phantom pilots, wrongly assuming that their ECMs would divert onrushing missiles, were unable to take evasive action in time.

For virtually every poison in jet-age aerial combat, however, there is an antidote. Though the Israeli-developed devices could not cope with the improved missiles, U.S. equipment has a larger number of frequencies. Washington has released more than a hundred ECM pods to Israel, each consisting of a bomblike container 10 ft. long and weighing about 300 lbs., which fits under the wing of a Phantom like an auxiliary fuel tank. Inside each pod are three canisters containing "noisemakers," or jammers, that radiate electromagnetic waves in the same frequencies used by the acquisition, tracking and terminal guidance systems* of an oncoming missile. When the ECM is turned on, the "noise" disrupts the missile's systems, causing it to veer away.

There is an electronic counter-countermeasure for jamming. Radio frequencies emitted by the ground-base guidance radar can be changed quickly so that the radar operator can continue to track the target aircraft on his scope in spite of the "noise." Of course, sensors in the ECM pod instantly detect this switch in hostile radar frequency and warn the pilot, who can then resume jamming by a frequency shift of his own. And on and on.

*Acquisition and tracking radar locks onto a plane and plots its position; terminal guidance radar navigates the missile to the target.

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