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]

The modifier per jammer

Jammer power	Jammer multiplier	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{ {e^{-(n/2.75)^{2}}} }[/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 2.938x 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.