F-35 Electronic Warfare: How the ASQ-239 Protects It

F-35 electronic warfare is handled by the BAE Systems AN/ASQ-239, a set of receivers and countermeasures built into the airframe that detects enemy radars, works out where they are and helps the jet avoid or attack them. It is the part of the aircraft that turns stealth from a passive property into a tactic.

A stealth jet survives by knowing where the radars are and staying outside the range at which each can see it. The ASQ-239 supplies that knowledge, without transmitting. This guide explains how F-35 electronic warfare works, what the jet can jam and where it still relies on other aircraft.

What is the AN/ASQ-239?

It is the F-35’s electronic warfare suite, made by BAE Systems in Nashua, New Hampshire. Ten antennas sit behind the leading and trailing edges of the wings and tail, shaped so they do not spoil the radar signature. Together they listen in every direction across the frequencies used by search, tracking and missile guidance radars.

The suite does four things. It warns the pilot when a radar is looking at the jet. It identifies the radar by comparing the signal with a stored library. It measures the direction of the signal precisely enough to place the emitter on the map. And it controls the countermeasures. For background on the subject, see what electronic warfare is.

How does the F-35 find enemy radars?

Passively. A radar has to transmit to work, and its signal can be detected at well beyond the range at which it gets a usable return from a stealth aircraft. The ASQ-239 picks up the signal, and two or more F-35s comparing bearings over their data link can fix the transmitter’s position in seconds.

That position goes into the fused picture described in F-35 sensors, with a ring showing the estimated range at which that radar could detect the jet. Pilots plan and adjust their routes around those rings. The same location is accurate enough to aim the radar’s ground-mapping mode or the targeting system at the site and then drop a guided bomb on it.

Can the F-35 jam radars?

Yes, within limits. Its jammer is its own radar. The APG-81 can put a narrow, powerful beam of noise or false signals onto an enemy radar that operates in the same band, which covers most fighter and missile guidance radars. Because the beam is narrow it is hard for others to detect.

The limits are frequency and direction. The radar antenna faces forward and works in one band. It cannot jam the low-frequency early warning radars that are best at detecting stealth aircraft, and it does not cover the rear. For protection in other directions the jet tows the ALE-70 decoy, which transmits signals designed to lure a radar-guided missile away, and it carries flares for infrared-guided missiles.

Does the F-35 replace dedicated jamming aircraft?

Partly. The US Air Force argues that an F-35 can enter defended airspace without a jamming escort, which older strike aircraft could not. The US Navy still pairs its F-35Cs with the EA-18G Growler, a dedicated electronic attack aircraft whose pods jam a much wider range of frequencies at high power, including the low bands.

The two approaches complement each other. The F-35 locates emitters from close in and shares the data; the Growler jams from further back. The F-35’s own ability to destroy radars will improve when the AARGM-ER anti-radar missile arrives, a step planned for September 2027 and covered in F-35 missiles.

Why do mission data files matter?

The suite can only identify a radar it has been told about. The details of each threat, and the best response to it, are held in mission data files written for a particular region. They are produced in reprogramming laboratories in the United States, including one at Eglin Air Force Base shared by Australia, Canada and the United Kingdom.

A new radar mode that is not in the file may be misidentified or missed. Keeping the files current is slow, specialist work, and customers other than Israel depend on the US-based laboratories for it. That dependence is one reason some buyers worry about how much control they have over their own jets.

Electronic warfare is also where the next upgrade lands first. Aircraft from production Lot 19 onward receive a reworked suite with new receivers and signal generators, according to the Pentagon’s testing office. How the whole approach supports low observability is explained in how F-35 stealth works.

Frequently asked questions

What electronic warfare system does the F-35 use?

The BAE Systems AN/ASQ-239, a suite of embedded receivers and countermeasures.

Can the F-35 jam enemy radar?

Yes. It uses its APG-81 radar to jam radars in the same frequency band, mainly in the forward sector.

Does the F-35 carry chaff and flares?

It carries flares and can deploy chaff, and it tows the ALE-70 decoy against radar-guided missiles.

Is the F-35 an electronic attack aircraft like the Growler?

No. Its jamming is narrower in frequency. The EA-18G Growler is a dedicated jammer covering more bands at higher power.

What is a mission data file?

A regional library of threat signals and responses that lets the suite identify what it detects.

Who makes the F-35’s electronic warfare suite?

BAE Systems, at its plant in Nashua, New Hampshire.