Electronic Warfare

Sensor Jamming

Sensor jamming attempts to overwhelm an opponent's search sensors (such as radars) to prevent one's detection.

When a Sensor jammer hits a shipborne sensor, it creates a "jammed volume" on that sensor. Given the distance between the jammer and the sensor [math]\displaystyle{ D_{j} }[/math] and the effect area ratio of the jammer, [math]\displaystyle{ E_r }[/math]. The jammed volume is a rectangular box centered on the jammer, with a length [math]\displaystyle{ =2D_{j} }[/math], and a width/height equal to [math]\displaystyle{ =2D_{j}E_r }[/math], with the length pointed toward the spotter. e.g. a jammer that is 5km away from a spotter will give that spotter a jammed volume 10km long and 4km wide.

If the sensor tries to spot a track within the jammed volume, the sensor will have to overcome the jamming power inflicted on it by the jammer.

Given the jammer's radiated power, [math]\displaystyle{ P }[/math], and gain, [math]\displaystyle{ G }[/math], the jamming power on a target at distance [math]\displaystyle{ d }[/math] is given by

[math]\displaystyle{ j = \frac{PG}{4\pi d^2} }[/math]

Multiplier per Jammer

Jammer power	Multiplier per Jammer	Total
Strongest Jammer	1.000	1.000
2nd Strongest	0.876	1.876
3rd Strongest	0.589	2.465
4th	0.304	2.770
5th	0.121	2.890
6th	0.037	2.927
7th	0.009	2.935
8th	0.002	2.937
9th	0.000	2.937

If a track is within multiple jammed volumes due to multiple jammers, the sensor will have to overcome the combined power of the jammers. The combined power is not a simple total, each additional jammer after the strongest will only add a fraction of its power to the final combined power. The power multiplier for a given jammer is calculated by [math]\displaystyle{ \exp \left( -(n/2.75)^2\right) }[/math], where [math]\displaystyle{ n }[/math] is the number of jammers imparting greater jamming power than this jammer. As a result, total jamming power will never exceed ~2.938× of the strongest jammer.

Detection range vs jammers

The distance that the jammer can be spotted by the target is found with the following formulas.

For a target (search) radar with:

• radiated power, [math]\displaystyle{ P_\text{t} }[/math]
• gain, [math]\displaystyle{ G_t }[/math]
• aperture size, [math]\displaystyle{ A }[/math]
• sensitivity, [math]\displaystyle{ S }[/math]
• and noise filtering, [math]\displaystyle{ \nu }[/math]

and with the jammer's cross-section being [math]\displaystyle{ \sigma }[/math] (in-game value divided by 10); and with [math]\displaystyle{ K = PG }[/math] from the numerator in [math]\displaystyle{ j }[/math] above (or the sum of multiple jammers, applying the stacking penalty),

the maximum distance for spotting the jammer, [math]\displaystyle{ d_j }[/math], is

[math]\displaystyle{ \begin{aligned} d_S &= \left(\frac{P_t G_t^2 A \sigma}{16\pi^2 (0.001)(10^{S/10})}\right)^{1/4}\\ & \\ d_N &= \sqrt{\frac{G_t\left(\sqrt{K^2 + \frac{(4\times 10^{-7})P_t A \sigma}{10^{\nu/10}}}-K\right)}{8\pi(1\times 10^{-7})}}\\ & \\ d_j &= \text{min}(d_S,d_N) \end{aligned} }[/math]

Countering Jamming

Remember that all kinds of signals lose power over distance by the power of 2. Applying that, consider a scenario where a hostile ship is jamming our search radar. As we move closer to the jammer two things happen:

• The jamming power increases by the 2nd power, [math]\displaystyle{ X^2 }[/math], since it needs to travel from the jammer to us.
• The return power increases by the 4th power, [math]\displaystyle{ X^4 }[/math], since it needs to travel from our radar to the jamming ship and then back to us.

Therefore, one counter to jamming is to simply move closer to the enemy.

Additionally, there are several tools available to raise the effective spotting range:

• Fire Control Radars such as the RF101 Bullseye or RF44 Pinpoint
• Burnthrough Sweeps from military search radars like the RM50 Parallax
• ELINT detection using the ES22 Pinard
• Illuminators, especially the E57 Floodlight
• High-power directional radars aka the R400 Bloodhound

Most jammers have a maximum effective range. Therefore, another way to counter jamming is to simply outrange it. This can be achieved with most long range radars, such as the RS41 Spyglass, Early Warning Radar, and R400 Bloodhound.

Most radars will be able to produce a line of bearing (LOB) toward any jammers that are affecting the radar. While the accuracy of this Jam LOB varies from radar to radar, and is rarely accurate enough for gunfire or other dumb weaponry, the LOB is still useful for quickly responding with counterfire, whether it be missiles, sending jamming back at the enemy, or just knowing where to close in.

Jamming only works on active radar sensors, and therefore sensors that don't need active radar will be unaffected, such as visual range (roughly 3km around every ship) or ELINT systems such as the Pinard.

Finally, friendly ships outside the enemy's jamming cone will be unaffected, and can easily spot the enemy formation and relay those tracks to the team automatically. As such, jammers provide a very powerful incentive for teams to spread out. A team spread across a wide area is much more resistant to radar jamming compared to a team that is tightly grouped, and is a method available to all fleets without needing to take one of the expensive tools listed above

Communication Jamming

Communication jamming in the game works by saturating the victim's receiving antenna, effectively denying them from receiving data from their allies.

Note that:

• Comms jamming does NOT stop a ship from transmitting its own information.
• Both comms jamming and transmission fall off as the inverse square of distance.
• While communication antennae are not occluded by terrain, comms jammers ARE occluded by terrain and can be blocked by rocks

In most cases, a comms reciever (such as a ship, a CMD missile, or a mine) is successfully comms jammed and isolated from the comms network if the jamming strength is greater than the transmission strength of the strongest ally transmission (out of all allies who are not also jammed). With one ship doing the comms jamming, we can find the distance required to successfully jam.

Given:

• The distance from transmitting ally to the target, [math]\displaystyle{ d_A }[/math]
• The transmitting ally's antenna strength, [math]\displaystyle{ P_A }[/math]
• The ally's antenna gain [math]\displaystyle{ G_A }[/math]
• The target's antenna gain [math]\displaystyle{ G_T }[/math]
• And with [math]\displaystyle{ K = PG }[/math] for the comms jammer (or the sum for multiple jammers; no stacking penalty),

Then the maximum distance, [math]\displaystyle{ d_c }[/math], at which the target is comms jammed is given by [math]\displaystyle{ d_c = d_A \sqrt{\frac{G_TK}{G_AG_TP_A - (4\times 10^{-7})\pi d_A^2}} \approx d_A\sqrt{\frac{K}{P_AG_A}} }[/math]

Only the simpler approximation is needed for normal situations. For example, if the target's allies are using CR10 antennas ([math]\displaystyle{ P_AG_A = 2500 }[/math]), then one Hangup jammer ([math]\displaystyle{ K = 7500 }[/math]) can jam at a distance [math]\displaystyle{ \sqrt{3} = 1.73 }[/math] times further than the transmitting ally. If the allies are using a CR75 ([math]\displaystyle{ P_AG_A = 30000 }[/math]), then one hangup has to be at half the distance as the CR75. Receiver gain is not factored in as receiver gain amplifies both incoming transmissions and incoming jamming, which effectively cancels it out except in the rare case where ambient noise is a significant factor (as gain does not amplify ambient noise)

In addition, ships within the same comms jamming cone (or sphere) will not be able to directly transmit to eachother, but the jammed ships can transmit out, and if an external ship can communicate in, the two ships will still be connected indirectly via the external relay ship.

+ Jamming vs Missile Successfully jamming a missile seeker (that is not equipped with a backup seeker) to the point where it detects no targets, will cause the seeker to follow a fake target and therefore causing the missile to drift off target.

further information: Missiles - Target Selection Cycle

+ Radar Illumination Radar illumination work in the game by painting targets inside the cone and generate a return signal. It is often used as guidance for SARH(Semi Active Radar Homing) missiles, but also aids in radar searching and locking.

Edge falloff

Most illuminators have "edge falloff"; this means that signatures near the edge of their cone will be illuminated less than signatures in the center of the cone. The falloff is calculated by [math]\displaystyle{ -1*(F_{alloff}*A)^2+1 }[/math] where [math]\displaystyle{ F_{alloff} }[/math] is the edge falloff stat of the illuminator, and [math]\displaystyle{ A }[/math] is how close the signature is to the edge of the cone (eg, at the very edge of the cone will be 1.0, at the center of the cone will be 0).

Edge falloff for most illuminators is 0.75, and therefore most illuminators will be reduced to ∼44% power at the edge of their fov.

Illumination angle

An Illuminator has to be within 90 deg offset from the radar for the radar to see the reflected illumination, if the illuminator is more than 90 deg offset, the radar will not be able to see the illuminator reflection and therefore will not benefit.

Viewing angle otherwise does not affect the reflected power, radars will receive the same amount of reflected power regardless if the illuminator is on the same ship or offset by 85 deg.

Soft Kill Decoys

The EA12 chaff decoy will burst into a cloud of radar-reflective chaff, creating a radar false-target with considerable RCS. This creates a stationary false contact on enemy and friendly radar, and also seduce ACT seekers of any type, and if it is located within the cone of radar illuminator, also has the chance of seducing SAH seekers. The decoy's signature starts out at ∼22,000m² signature and decays over time, down to ∼14,500m² after 38 seconds, and rapidly down to ∼3,300m² when it expires after 45 seconds.

The more expensive EA14 decoy exclusive to OSPS works in a similar way, but has ∼40,000m² sig instead, and decays down to ∼26,400m² after 38 seconds, and down to ∼6,000m² when it expires after 45 seconds.

The EA20 flare decoy upon deployment will spray out a cloud of hot particles that seduce WAKE seekers. This decoy decays over time, down to 85% after 24 seconds, and down to 15% when it expires at 40 seconds

The EA99 active decoy exclusive to ANS imitates ship active and passive signature, seducing ACT ARAD and SAH(if illuminated). The decoy travels in a direction for 30 seconds before it expires and has a constant signature. Different from chaff, the active decoy is programmed to exactly imitate the RCS of the launching ship^{[Needs Confirmation]}, making it more effective for ships with large RCS. However, the active decoy does not reflect illuminators well, and therefore may struggle to attract SAH in certain cases. While EA99 decoys will not be fired by the decoy button, they can be fired manually from the EWAR menu (although their slow speed and short range limits the utility of this function) >could someone check expire time?

ELINT

[wip]

ELINT detectors (such as the Pinard) allows a ship to passively detect enemy radar emissions, such as those from search radars or fire control radars, at up to 1.25x of that radar's max range. One ELINT module will show a rough line of bearing toward the emitter, while two will produce a crossfix. ELINT will also be able to identify what type of radar it is (or more specifically, it can reveal the ELINT category of the radar) and will display it on the ELINT LOB or crossfix. If the ship is equipped with multiple types of radars, the track will display all detected types.

The categories are generally self explanatory, most internal search radars (spyglass, huntress, etc) are Search/Track. All turreted fire control radars (Bullseye, Pinpoint) are Fire Control. The Early Warning Radar is the only radar that will be specified as Early Warning. Parallax using the locking function will still classify as Search/Track. Bloodhound is classified as Search/Track

Most directional radars like FCRs also have sidelobe patterns, allowing ELINT to detect these radars at reduced range even if they're not pointed at the ELINT set. These sidelobe patterns can be viewed on the respective component page.

ELINT is not able to detect integrated FCRs on PD turrets

ELINT is not able to detect illuminators.

ELINT is not masked by hull, and a double ELINT setup will not have a blindspot between the ELINT sets (as ELINT is measured from the center of the ship rather than from the set itself).

Trivia

• Due to the modelling of the E70 Interruption Jammer, it is nicknamed as "disco ball".

External Links

• NotSoLoneWolf's Radar Calculator V7 - can simulate radar and comms jamming across a wide variety of parameters