# Reading — From Radar to EW By the end of this lesson you should be able to: 1. Map each term of the radar range equation to the **EW lever** that attacks it. 2. State the roles of **ES**, **EP**, and **EA** with doctrinally correct examples. 3. Explain the **one-way vs two-way** detection asymmetry and why it favors the listener. 4. Navigate the **Block 2 roadmap** from ES through EA to Project 2. ## Same physics, opposite agenda Block 1 put you in the threat's seat. You can now compute exactly how an integrated air-defense system sees the B-21 — aspect by aspect, band by band, kilometer by kilometer. Block 2 flips the seat. The physics does not change; the *agenda* does. Where Block 1 asked "how far away does this radar detect the bomber," Block 2 asks "what can we do to that radar — listen to it, hide from it, lie to it, or drown it out." Electromagnetic warfare is the discipline of fighting *in and for* the spectrum, and it turns out that every variable you learned to compute is also a variable you can attack. ## The range equation is a target list Look again at the maximum-range form from L3 and L8: $$ R_{\max} = \left[\frac{P_t\,G_t\,G_r\,\lambda^2\,\sigma}{(4\pi)^3\,S_{\min}}\right]^{1/4}. $$ Read left to right, it is a physics formula. Read as an EW operator, it is a list of things you can do something about: - **$\sigma$ — shrink it by design.** Low-observable shaping and radar-absorbing material cut the target's radar cross-section. This is *protection* (EP), and it is the Block 1 story. - **$S_{\min}$ — raise their effective noise floor.** Noise jamming injects energy into the threat receiver so the minimum *detectable* signal climbs. This is *attack* (EA). - **$G_t, G_r$ — enter where they aren't looking.** Every antenna has side lobes (L6). Energy injected through a side lobe still reaches the receiver. Also EA, and the thing EP works hardest to close off. - **$P_t$, $\lambda$, PRF — every emission leaks intent.** A radar *must radiate* to work, and the moment it does, its frequency, pulse width, and PRI announce what it is. Collecting that is *support* (ES). :::{admonition} Key Concept :class: key-concept Block 1 taught you the range equation. Block 2 teaches you to fight it. Every factor that sets detection range is also a lever — one side designs to shrink $\sigma$ and protect $G_r$, the other designs to raise $S_{\min}$ and exploit emitted $P_t$. ::: ## The three pillars EW doctrine divides the discipline into three pillars. You met them in L1; here they get their working definitions. - **Electromagnetic Support (ES)** — *sense* the spectrum to support targeting, warning, and intelligence. On-board radar warning receivers (RWR) and off-board SIGINT/ELINT assets exploit the threat's one unavoidable weakness: a radar must radiate to function. ES feeds everything else — attack needs cueing, and routes need known threat locations. (Legacy term: ESM.) - **Electromagnetic Protect (EP)** — *defend* our own use of the spectrum, against both enemy attack and friendly interference. Low-probability-of-intercept (LPI) waveforms, frequency and polarization agility, side-lobe cancellation, hardening, and LO all live here. (Legacy term: ECCM.) - **Electromagnetic Attack (EA)** — *deny, degrade, or deceive* the enemy's use of the spectrum. Noise jamming brute-forces the $S_{\min}$ term; deception (DRFM false targets) lies to the tracker instead of shouting at it; expendables (chaff, flares) give the seeker something better to chase; and counter-PNT attacks GPS. (Legacy terms: ECM and, confusingly, "EW.") A clean way to keep them straight: **ES senses, EP defends, EA attacks — and ES feeds the other two.** ## The listener's advantage The single most important asymmetry in EW follows directly from the range equation's exponents. A radar's energy must make a *round trip* — out to the target and back — so the echo power it works with falls off as $1/R^4$. A radar warning receiver only needs the signal to *arrive*; it hears the one-way transmission, whose power falls off as only $1/R^2$. Same transmitter, same instant: the listener wins by orders of magnitude. Run the numbers for the Block 1 threat classes against a B-21-class target and the radar's detection range is tens of kilometers while the RWR's intercept range — by the math alone — runs into the thousands. In practice the RWR's true limit is the **radio horizon** (a few hundred kilometers at altitude), not its sensitivity. That detail *is* the teaching point: the listener's detection problem is solved by geometry, while the radar's is bounded by hard physics it cannot escape. :::{admonition} Key Concept :class: key-concept The radar pays $R^4$ to see you; you pay $R^2$ to hear it. A passive receiver detects a radar far beyond the range at which that radar could ever detect the receiver's platform — which is why standing off and listening is the opening move of EW. ::: ## The endless cycle No EW technique is permanent. The discipline advances as a move–countermove tree: - **Action** — the radar innovates: pulse-Doppler, frequency agility, LPI. - **Reaction** — countermeasures answer: noise jammers, chaff, DRFM deception, LO. - **Counter-reaction** — protection closes the loop: hopping, side-lobe cancellation, adaptive processing, multistatic radar. Several Block 1 topics were themselves moves in this game — MTI and pulse-Doppler answered chaff and clutter; low-band early-warning radars answer LO. EW is decided as much by *speed of adaptation* as by hardware, which is why Block 2 is organized as a tour of this tree rather than a catalog of gadgets. ## Block 2 roadmap - **ES (L12–L14):** RWR architecture, angle of arrival, triangulation and fusion. - **EP (L15–L16):** LPI radar, frequency agility, side-lobe cancellation, and spread spectrum for communications. - **EA (L17–L18):** the jamming taxonomy, J/S and burn-through, and DRFM deception. - **Project 2 (L19–L20):** a B-21 standoff emitter-geolocation analysis — design it, run it, defend it. HW2 and Quiz 2 land with the Project 2 presentations at L20, the same rhythm as Block 1. ::::{admonition} Quick Exercise :class: quick-exercise For each desired effect, name the pillar (ES / EP / EA) and the range-equation term it works through: 1. Make the TTR's screen bloom with noise during the ingress. 2. Locate the SA-21's acquisition radar from 200 km away without transmitting. 3. Keep the B-21's own radar usable while the enemy jams the band. 4. Convince the tracker the B-21 is 2 km left of where it actually is. :::{admonition} Solution :class: dropdown 1. **EA** — noise jamming raises the threat's effective $S_{\min}$. 2. **ES** — passive geolocation exploits the radar's emitted $P_t$ at one-way $R^2$; no transmission of your own. 3. **EP** — agility, LPI, and side-lobe management protect your own $G_r$ / $S_{\min}$. 4. **EA** — DRFM *deception* attacks the tracker's measurement, not its power budget. Note the contrast with noise jamming: deception lies, noise shouts. ::: :::: ## Wrap-Up The radar range equation is a target list: every term — $\sigma$, $S_{\min}$, the gains, the emitted parameters — is something one side designs to protect and the other designs to exploit. ES senses, EP defends, EA attacks, and ES feeds the other two. The discipline rests on the one-way/two-way asymmetry: the listener detects at $R^2$ while the radar pays $R^4$, so passive standoff collection is the opening move. And no move is final — every technique has a counter. Next, **L12** opens the box that does the hearing: the radar warning receiver, inside and out.