Report 161 · Defense Tech
Popular writing about electronic attack says a jammer "blinds" a radar or makes an aircraft "invisible." The Navy's own engineering handbook describes something more modest and more interesting. A jammer doesn't erase the target. It moves the range at which the radar can find it. Somewhere between the radar and the jammer there is a distance where the radar's echo wins again, and that distance has a name: burn-through range.
Here is how the idea usually reaches the public. A 2016 Fox News piece on the Navy's Next Generation Jammer said US forces can deploy jammers "making aircraft and troops 'invisible' to enemy tech." A 2025 National Interest explainer on jamming pods said a pod emits signals to "confuse, overload, or blind the enemy system." Neither is crazy as shorthand. Both hide the one thing an electronic warfare officer actually plans around, which is that jamming is a contest that changes with distance, and the jammer loses it if the target gets close enough.
The clearest public source for this is the Naval Air Warfare Center Weapons Division's Electronic Warfare and Radar Systems Engineering Handbook (NAWCWD TP 8347), a free, unclassified reference cleared for public release. Its own foreword says it exists to help engineers make "general estimations regarding capabilities of systems." Everything below comes from its sections on jamming-to-signal ratio (4-7) and burn-through range (4-8).
A radar finds a target by listening for its own pulse coming back. That pulse has to travel out to the target and back again, and it spreads out both ways. The handbook's two-way radar equation puts the returned signal, S, falling with the fourth power of range: double the distance and the echo drops to one sixteenth.
A self-protection jammer sits on the target and transmits straight at the radar. Its signal, J, only makes the trip once, so it falls with the square of range: double the distance and the jamming drops to one quarter.
Divide one by the other and range doesn't cancel. The handbook's equation for the jam-to-signal ratio against a conventional radar has J/S growing with the square of the distance between radar and target. On a log plot of power against range, the handbook draws jamming as a line falling at 20 dB per decade and the echo as a line falling at 40 dB per decade. Two straight lines with different slopes cross somewhere. Far out, the jammer is louder than the echo. Close in, the echo is louder than the jammer.
That crossing is what the handbook calls crossover range, where J equals S. Burn-through is the related point that matters in practice:
Burn-through Range is the radar to target range where the target return signal can first be detected through the jamming and is usually slightly farther than crossover range where J=S.
It is usually farther because a jammer generally needs to beat the echo by some margin to work, not just match it. The handbook calls that margin the minimum effective J/S, and it depends on the technique and on the radar.
Section 4-8 illustrates this with a sample radar and jammer: a radar transmitting 80 dBm (100 kilowatts) through a 42 dB antenna, a target with a radar cross section of 18 square metres carrying a 50 dBm (100 watt) jammer through a 6 dB antenna. The handbook gives crossover at about 1.29 nautical miles. I reran its crossover equation with those inputs and got the same 1.29 nautical miles, about 2.4 kilometres.
Then it assumes the jamming needs to be 6 dB above the echo to work, and reads burn-through from its sample graph at about 2.8 nautical miles. When I solve the burn-through equation directly I get closer to 2.6 nautical miles, because a 6 dB margin is a factor of four in power and the range scales with its square root, so burn-through lands at almost exactly twice crossover. The handbook labels that chart as a sample that "cannot be used for data," so I would trust the equation over the drawing. Either way the lesson is the same. Inside a couple of miles, this particular radar sees this particular target through this particular jammer.
One detail in that section surprises people: crossover and burn-through ranges do not depend on frequency. The handbook says so plainly, noting that "both ranges are independent of frequency," because the wavelength terms cancel when J is divided by S.
The burn-through equation in section 4-8 puts range under a square root. Inside that root, the radar's power, its antenna gain, the target's radar cross section and the required J/S margin all sit on top, and the jammer's power and antenna gain sit on the bottom. This is my arithmetic from that equation, not a table in the handbook, but it follows directly:
The handbook makes the design point from the radar's side in one line: "A radar can be designed with higher than necessary power for earlier burn-through on jamming targets." And it makes the counterpoint from the jammer's side in section 4-7. More jamming power, it says, rarely makes a technique more effective at a given range, and against some modern radars too much J/S can cause the processor to ignore the jamming or switch on anti-jam modes. What more power buys is distance:
Increasing "J-to-S" (or the jammer power) does, however, allow the target aircraft to get much closer to the threat radar before burn-through occurs, which essentially means more power is better if it can be controlled when desired.
That sentence is the whole correction to "invisible." A jammer buys an aircraft room. It never buys it all the way to the radar.
The handbook separates self-protection jamming, where the jammer rides on the target, from support jamming, where one platform screens another. A stand-off jammer orbits far from the radar, usually beyond weapons range; a stand-in jammer is a remotely piloted vehicle orbiting close to it. The handbook's comment on the difference is blunt:
Obviously, the jamming power required for the SOJ to screen a target is much greater than the jamming power required for the SIJ to screen the same target.
The geometry explains why. A stand-off jammer's signal travels a long way to reach the radar while the striker it protects keeps closing, so the striker's echo keeps strengthening while the jamming it is hiding behind does not.
There is one more thing "invisible" gets backwards. A self-protection jammer is a transmitter, and transmitters can be tracked. The handbook's glossary defines home-on-jam as a means by which "a missile guidance receiver utilizes the self-screening target jamming signal to develop angular steering information so that the missile can home on that target." Jamming can deny a radar its range measurement while advertising the jammer's direction. Deciding when to transmit is part of the job for exactly that reason.
My first career was counter-IED and electronic warfare, and the habit that trade builds is to think in link budgets rather than in adjectives. No jammer I ever worked with was described in the field as making anything invisible. It was described by who it could overpower, at what distance, and what it gave away while it did.
The same reasoning shows up on this site's drone reports, with one change worth flagging. Against a radar, the jammer gets the one-way head start described above. Against a drone's radio link, both the controller's signal and the jammer's signal make a one-way trip, so neither falls faster than the other. Going by the handbook's one-way range equation, which side wins then comes down to power, antenna gain and how close each transmitter is to the receiver. That is my reading of the one-way equation, not a worked example the handbook gives for drones. It is also the contest behind the counter-IED jammers I wrote about in what a jammer can't stop.
Which copy I read. The Defense Technical Information Center refused automated downloads, so I read the full 455-page PDF of the fourth edition (October 2013, marked "DISTRIBUTION STATEMENT A: Approved for public release") from a public mirror, listed below, and extracted the text of sections 4-7, 4-8 and the section 4-13 glossary directly. I have not compared it page by page with the DTIC record.
The numbers are a sample, not a real system. The 1.29 and roughly 2.6 nautical mile figures come from the handbook's illustrative radar and jammer. They say nothing about any fielded radar, aircraft or jammer, and real burn-through depends on antenna patterns, processing, polarisation, losses and the jamming technique, all of which the handbook discusses and the simple equation leaves out.
The two press examples are illustrations, not a survey. I quote them to show how the idea is usually phrased, not to claim that all coverage gets it wrong.
A jammer doesn't delete an aircraft from a radar screen. It trades on geometry: its signal only has to travel one way, the radar's echo has to travel two, and so at long range the jammer wins. Close in, the echo wins, and the distance where that happens is the burn-through range. Doubling jammer power moves it by less than a third. Next time you read that a jammer makes something invisible, the useful question is: invisible out to what range?
Scope note: this report explains textbook radar and jamming relationships from a publicly released US Navy engineering handbook. It uses only the handbook's illustrative numbers and evaluates no fielded radar, aircraft, jammer or program. The author has no role in any electronic warfare program and no financial interest in any company in this field. Nothing in this report describes how to defeat, degrade or evade any specific system.
U.S. Army combat veteran (Counter-IED / Electronic Warfare), peer-reviewed researcher in microwave spectroscopy, and founder & CEO of Shroombiosis. Consults on laboratory operations, AI, and supplement formulation.