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From AGSI - Harpoon/H3 MilSim
Electronic Counter-Measures (ECM)
If a ship or aircraft is equipped with ECM equipment it can be used to degrade enemy sensors. Select Active from the Sensor dialog box to activate the ECM. Remember that in many cases, using ECM will degrade your sideâ€™s sensors as well. When a unit or group is being jammed a small â€œXï¿½? will appear in the upper-right side of the unit or group symbol. If a unit or group on another side is using jammers a small â€œQï¿½? will appear in the upper-right side of the symbol for the unit or group using the jammer.
ECM (now called Electronic Warfare in the US) falls into two broad categories; noise jamming and deception jamming. Noise jamming seeks to blot out the signal in a manner similar to shining a flashlight in your eyes. It can cover a broad spectrum (called barrage jamming) or specific frequencies (called spot jamming). IRL, the best counter to spot jamming is frequency agility which gives the jammed sensor the ability to operate outside the frequencies that are being jammed. This is made harder at higher frequencies (such has the NATO K-Band [US Ka and Ku Bands]) because the higher the frequency the broader the range of frequencies that the jammer must cover.
Noise jamming is generally used to screen formations of aircraft and ships in which a jammer will generate enough power to make it impossible for the other side to distinguish a near-by High Value Unit (HVU).
Deception jamming generally depends on a more involved analysis of the radar to be jammed. Because the jammer must send back a false echo, then systems on board the jammer must be able to monitor the Pulse Repetition Frequency (PRF), scan rate, and pulse width. The idea being to send back signals that will fool the radar into creating a false contact either by altering the range (range-gate pull off), speed (velocity-gate pull off), or bearing (by sending a signal down the radars side lobes). This is mainly a battle between hardware sophistication and it's associated software.
ECM in Harpoon4 Minatures
Because of the complex and highly classified nature of ECM, Harpoon4 uses a simplified approach, building in the effects of RCM into weapon PK values and radar detection capabilities. Although some information is available for many of the sytems in use, knowledge of their combined use is limited, and the effects of both sides using chaff, jammers, deception repeaters, and flares all at the same time can only be guessed at. The accent on Harpoon4 is simplicity, and given the accuracy of unclassified information available, this approach gives a reasonably accurate approximation of the effectiveness of electronic or acoustic countermeasures.
ECM actions (turning on jammers, deplying chaff) must be ordered in the plotting phase of a turn. Exact employment tactics are not necessary as it's assumed the countermeasures are used correctly.
In H4 play, stand off jammers like ALQ-99 will automatically degrade all radars by a certain percentage of their range (typically 50 to 75% depending on the generation of the system and how many pods [jammers] there are).
Self protection jammers will apply a PK reduction similar that used by chaff or flares. Users are advised that to consult the H4 rules (specifically pages 6-31 and 6-32) for further information on Electronic Warfare.
Offensive ECM in Harpoon III ANW
Harpoon III is only capable of barrage and spot type jamming. In most databases, jammers cover a large spectrum area. Spot jamming is possible to a limited extent along a frequency-band by frequency-band basis. In other words, spot jamming can cover only one frequency band at a minimum and cannot cover any part of that band. Achieving burn-thruough is a function of the value in the Passive Input value applied to a 75% reduction in the detection range of the radar.
The search output field of the ECM sensor will now determine the strength of the jammer in relation to detection by ESM.
In laymans terms, ECM now results in a flat reduction of 75% of the detection range of the radar vs a given target (in the case the targets radar cross section). The Passive Input value of the radar will stipulate the ECCM capability of the radar in a percentage reduction of the flat 75%.
It's important to note that radars that are phased arrays will have their range penalty reduced to 25% because of the electronic steering capability that phased arrays possess. A flag is available in the database editor to apply to the radar.
It's important to note that the 75% reduction applies to detection range only and not to the cross section value of the target being searched for. So if a radar would normally pick up a target at 100nm then under jammed conditions it would pick it up at 25nm. Phased arrays would pick up the target at 75nm and a radar with an ECCM rating of 25% would pick up the target at 50nm (75% - 25% = 50% range reduction). Either way, maximum jamming range is set by the radar horizon of the jamming platform.
Visual sighting overrides ECM. If the target enters visual range prior to burn through then it will be detected and ECM will be moot. The default visual setting (i.e. the lookout on the ship, unassisted by optical systems) is -650.
Single Platform Radar Horizon is calculated by using the following formula:
[2 x (4/3rds radius of the earth) x altitude]^0.5
Where the radius of the earth is 6,379,155 meters Altitude is also in meters
This means for an aircraft at 10,000 meters (32,800 feet) then the radar horizon is 222.7 nautical miles.
For Two Platforms at different heights, the following equation is used:
[(2.21 x Square Root of Mast Height/Altitude 1 in Meters) + (2.21 x Square Root of Mast Height/Altitude 2 in Meters)]
An automated web based radar horizon calculator can be found at http://radarproblems.com/calculators/horizon.htm
Defensive ECM in Harpoon 3 ANW
While OECM uses the search output value to determine strength, DECM uses the track output value to determine a flat PK reduction applied against the weapon attacking the platform.
H3ANW like the Harpoon minatures rules uses a generational aspect when it comes to DECM:
1st Generation DECM = 5% PK reduction against the attacking weapon 2nd Generation DECM = 10% PK reduction against the attacking weapon 3rd Generation DECM = 15% PK reduction against the attacking weapon 4th Generation DECM = 20% PK reduction against the attacking weapon and so on if you wish....
These values (the 5 to 20) are applied to the track output field of the DECM sensor. The modifier will show up in the weapon calculation upon impact. It has no affect prior to that.
ECM and Database Editing
In game ECM has no range other than the radar horizon, and the game engine will not observe the maximum range field of the sensor annex. At this time the user will have to calculate manually, based on altitude, the maximum effective range of the jammer. Database authors are advised that we are looking at creating a range ring (per se) for ECM based on the radar horizon but it will not provide an accurate representation of what's jammed and what's not since that is dependant on radar output values. We can only guarantee that platforms OUTSIDE the range ring will not be jammed.
DB authors are also reminded that all values in the output values for the jammer (and radars too) must be positive. There will be strange weapons effects (100% effectiveness of countermeasures) should the value be negative. This also applies to the ATA and PK values of decoys.
EW System Specifications
ECM Systems AGSI Wikipedia Database of Military ECM Systems.
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