DCS and Electronic Countermeasures: Table of Contents
- Part I: Electronic Countermeasures – Introduction
- Part II: F-14 Avionics
- Part II: Missile Employment
This topic, in real life, is complex and often classified for obvious reasons. Therefore, no one expects a loyal representation of the jamming techniques and mechanics in a video game, albeit reaching a solid compromise should not too complex (or is it?).
This Part aims to introduce the topics of ECM and jamming, then moves to cover the beloved F-14 Tomcat, reporting accounts and experiences. The following Parts will discuss the tools available to the virtual Radar Intercept Officer in DCS.
ECM: Underrated Master of the Battlefield
Through recent history, Electronic Warfare have been a key component of aerial superiority. Deceiving the enemy is fundamental to degrade their situational awareness, limit their weapons capabilities, manoeuvre and surprise the hostile defences.
Perhaps the greatest example of EW application, both in scale and effectiveness, is the first Gulf War, but the history is very long and probably started with the usage of Chaffs to confuse and saturate radars in WW2. As the technology (and wars) progressed, from Korea, Vietnam, operations in Syria and Libya to ex Jugoslavia, dedicated support aircraft were introduced, such as the EF-111A Raven, or the EA-6B Prowler, to the EF-18G Growler. As their names suggest, these are dedicated variants of the F-111 Aardvark, the A-6 Intruder, and the F/A-18 Hornet. They provide what is referred to as “Escort Jamming”.
In parallel, smaller and less powerful devices were developed, each capable to provide individual self-protection to the aircraft. Examples of these devices are the AN/ALQ-165 ASPJ (Airborne Self Protection Jammer) mounted in the F/A-18 Hornet, or the AN/ALQ-100 and 126 DECM (Defensive Electronic Countermeasures) mounted in the later versions of the F-14 Tomcat.
Both types of asset and devices are used in real life, but in DCS only self-protection devices are implemented, and those devices try to emulate just the very basic features of noise jamming.
Jamming Techniques Overview
Types and Purposes
Electronic Countermeasures fall into two main categories: Noise and Deception, each containing a number of subcategories.
In simple terms, Noise focuses on negating information to the attacker by using different techniques and resulting in the saturation of the target radar, thus denying its ability to determine range (primarily), azimuth and elevation (occasionally).
Deception, as the name suggests, aims to manipulate signals to provide wrong data about range, azimuth, or velocity.
Ultimately, the objective of Electronic Countermeasures is negating or corrupting the target’s Situational Awareness and weapon employment, giving an immense advantage to the jamming aircraft and faction.
No matter which type of jamming is used, there is a series of common incognita that should be satisfied in order to ensure successful jamming. These parameters include the frequency (jamming and target’s frequency must coincide), J/S ratio (jamming-to-signal), S/N ratio (signal-to-noise) and the more interesting from a gaming perspective, the burnthrough range.
Signal-to-Noise, Jamming-to-Signal ratio and Burnthrough Range
The concept of Signal-to-Noise ratio is quite familiar. We run into it very often, for example when troubleshooting broadband issues, or working with amplifiers.
(raise your hand if you have PTSD induced by studying hybrid-parameters amplifiers in high school!)
Jumping back to jamming, in this context the S/N ratio represents the ability of a radar to spot targets. Moreover, it indicates how the radar is vulnerable to determined jamming techniques, in primis noise jamming. In this sense, S/N also describes the “weakness” to jamming.
To understand which variables play a role in the S/N ratio, let’s have a look at the following equation:
PT : transmitted power;
G : antenna gain;
σ : target RCS;
Ae : antenna aperture area;
R : range to target;
K : Boltzman constant;
T : standard temperature [K];
B : radar received equivalent bandwidth;
F : radar receiver noise figure.
This equation tells which parameters affect S/N positively: transmitted power, antenna gain and aperture, a decrease in range. Note also how the range is the denominator, and the exponent is 4.
As mentioned, at the moment, the range is basically the only variable players can directly use to impact hostile jamming. In real life, instead, the matter is much more complex.
The other side of the discussion is the “strength” of the jamming signal, or how effective it is. As long as the power of the jammer is greater than the power of the return signals, the target’s radar is affected.
PJ : jamming power transmitted;
GJ : jamming antenna gain;
PT : peak power transmitted by radar;
GT : radar antenna gain;
R : jammer to radar range;
σ : aircraft RCS.
Some parameters, such as the RCS or the range, appear again. In particular, the range has now exponent 2.
The range is an important factor when it comes to electronic warfare. As we have noticed, the range in the S/N ratio has exponent 4, whereas in the J/S ratio has exponent 2. This represents how the signal from the radar has to travel twice the distance of the jammer’s signal. Why? Because a conventional radar works by illuminating a target, and evaluating the returns. Thus, the distance is travelled twice (radar → target, then target → radar). The jammer, instead, sends signals towards the radar, and the signals cover the distance only once.
This means that airborne transmitters can emit much less power than ground-based installations, and still be very effective.
As the range decreases, at a certain point, the signal reflected is strong enough to overcome the jammer. From that point forward, the jamming is ineffective, and the target is detectable by the radar. This particular range is called “burnthrough range“.
Note that in real life this may not be necessarily the case, but in DCS, which depicts only noise jammers, past the burnthrough range, the jamming is de facto set to zero.
In other words, the closer the jammer and its victim are, the less and less effective the jamming becomes (noise jamming in particular). Vice versa, the power of the reflected signal on the jamming aircraft increases. When the balance shifts, and the reflections are too powerful to be masked by jamming, the jamming aircraft becomes “visible” to the target radar.
Parenthesis: Noise Jamming & DCS
Noise jamming is the type of electronic countermeasure implemented in DCS at the moment. Its objective, as the name suggests, is creating a disturbance aimed to obscure the jamming aircraft’s returning signal, negating range.
There are several techniques to implement different type of noise jamming. Barrage, spot, swept-spot are a few examples, and more parameters that dictate its effectiveness, such as J/S ratio, power density, quality of the noise signal, polarization.
In DCS, individual ECM devices, such as the mentioned AN/ALQ-100 / 126 DECM, de facto behave as all-around jamming strobes, something that should not be. It is interesting to note that, jamming, to be effective, should be producing continuous interference. This is a giveaway of the depth of DCS’ implementation, which has improved during the years, but it is still very simplistic (some may remember the days when toggling the ECM in FC3 aircraft was sufficient to break any lock…).
Being Jammed: Considerations
Being on the receiving end of a jammer is not as dire as it may sound (at least when gaming is involved): a jamming target does not disappear into thin air, quite the opposite.
Techniques exist capable of guiding a missile onto the source of a jamming signal (“Home-on-Jam“). This means that noise jamming may prevent or break or a lock, but the missile can still be dangerous. An HoJ-capable missile, in fact, can counter an aircraft’s jamming by identifying the signals and homing onto a jamming source.
When a radar is jammed in DCS, the range may not be available until the burnthrough range, but in case of shots within such distance, the jamming aircraft will make itself much more visible by maintaining the ECM device active. In fact, it can even hinder defensive manoeuvres, making them less effective, as the missile will simply fly towards the very loud and shiny signals, and the signals may spike even when notching or thourgh other blind spots.
Running through the F-14’s manual, we find that, for instance, the AWG-9 can track a jamming aircraft, depending on the jamming technique and power, via angle-tracking. The real Radar Intercept Officers had several tools they could use to mitigate the effects of a jamming aircraft (SPL, ALT DIFF, VGS, for example).
For example, the range can be estimated via TCS and angles via the mentioned jam angle-tracking (JAT). These data can be enough for the RIO to employ a missile against the jamming target, and estimate the odds of success.
As mentioned, the next part of this discussion will cover the tools available to the F-14 crew that allow them to counter, or mitigate, the effects of jamming. It will be interesting to find which and what has been implemented!
F-14 Tomcat vs Jamming: Accounts
According to many sources, the F-14 Tomcat was, at the time of its introduction and for several years, a really tough customer when it came to jamming it. Although, as usual, personal accounts should always be taken with a grain of salt.
For example, during the testing phases, in 1973, the longest known air-to-air missile intercept was achieved by an F-14 and the AIM-54 Phoenix. The F-14 intercepted a simulated Tupolev T-22 Backfire. The target was flying at 52,000ft at a speed of Mach 1.55; the F-14 at Mach 1.45 at 45,000ft. The AWG-9 detected the Tupolev in Track-While-Scan at 132nm.
The Phoenix was launched at 110 nm, the missile reached an altitude of 103,500ft, before passing 5ft from the target (!) at 75nm.
The simulated bomber was also using an on-off blinking noise jammer, but failed to jam the AIM-54 Phoenix.
For us Prowler ECMOs the AWG-9 was one hard radar to jam. But more important than the gadget itself was the knob-twisting RIO you were dealing with.
The Iran-Iraq war, started in the early 80s and concluded in 1988, also tested the resilience and the capabilities of the F-14 Tomcat and their Radar Intercept Officers.
A good testament of these abilities, is the engagement occurred on the 01/12/1982, when an F-14 crew engaged a MiG-25RB, which tried to hinder their effort by activating its ECM at a distance of 38 nm. Nevertheless, the F-14 RIO managed to obtain a solid lock at 34 nm, resulting in the employment of an AIM-54 and destruction of the Foxbat.
“During the whole war, I never heard of the AWG-9 radar being successfully jammed. There were a handful of cases of radar lock-on being broken by close-range manoeuvring or by MiG-25s using their high speed to outrun an F-14, but the Iraqis (using French equipment) and the Soviets never managed to jam our radars. They expended considerable effort trying to do so, using different systems.”
“They tried deception, barrage, spot and overload jamming, but they weren’t successful. Our radars had a high basic working frequency and excellent frequency agility, so it was easy to move the radar away from the jamming signals and reject those which didn’t match the precise search form pattern of our AWG-9. On several occasions, they tried overwhelming us by combining all these methods. I once detected 11 jets closing simultaneously on me using jamming, but this posed no great problem, as my AWG-9 could handle twice as many targets simultaneously. And my RIO and I solved the jamming within seconds.”
Given these premises, the question is how well the virtual F-14 Tomcat behaves compared to the real one. Will its crazy-powerful radar have an edge against enemy jamming devices? Will the tools available to the Radar Intercept Officer allow him to achieve victory in a complex fight?
The answer will have to wait for the release of ECM/Jamming effects in DCS.
If you are looking for a more comprehensive and in-depth material, there is a plethora of publications available. They span from the physics / maths basics, to the military application at different levels.