¶ Communications – MADL, Link-16, SATCOM

¶ Why Does the F-35 Need Data Links?

A modern combat aircraft does not operate in isolation. It is part of a network comprising other aircraft, ground stations and command centres. This networking – known as Network Centric Warfare – allows an aircraft to utilise not only its own sensors but also the data from all other participants in the network. The result is a shared situational picture (Shared Situational Awareness) that goes far beyond what a single aircraft could detect on its own [39].

The F-35 features three fundamentally different communication systems that differ significantly in their operation, performance and stealth compatibility.

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¶ The Three Communication Systems at a Glance

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¶ MADL: The Invisible Data Channel

¶ What is MADL?

The Multifunction Advanced Data Link (MADL) is a data link developed exclusively for the F-35 [38]. It operates in the Ku-band (12–18 GHz) and uses directional phased-array antennas that transmit signals in extremely narrow beams (so-called pencil beams with less than 2° beam width).

¶ Why is MADL Stealth-Compatible?

The decisive difference from Link-16: MADL transmits its signals not in all directions but only in a targeted manner towards the receiver. An adversary would have to be positioned exactly within the narrow beam cone to intercept the signal – which is very unlikely in practice. The low transmit power and narrow beam make detection even with specialised surveillance systems possible only at short distances (under 50 km) [38].

¶ How is MADL Used in Operations?

When multiple F-35s fly in formation, they automatically exchange the following data in real time (latency under 50 ms) via MADL:

• Sensor data: Radar imagery, infrared detections, electronic warfare warnings
• Target coordinates: One aircraft detects a target, another can engage it (Shooter-Sensor Separation)
• Status reports: Position, fuel, weapons inventory, system status

This turns a group of F-35s into a networked sensor system that can detect and engage far more than any single aircraft.

¶ Limitation

MADL works exclusively between F-35s. It is not compatible with other aircraft types (Rafale, Eurofighter, F-16), not with ground stations and not with AWACS surveillance aircraft. For any communication outside the F-35 formation, a different system is required [39].

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¶ Link-16: The NATO Standard and Its Stealth Problem

¶ What is Link-16?

Link-16 is the standardised NATO tactical data link, defined in STANAG 5516 [46]. It enables data exchange between virtually all Western military platforms: combat aircraft, AWACS, warships, air defence systems and ground stations. Link-16 operates in the L-band (960–1,215 MHz) and uses a frequency-hopping method across 51 channels at over 77,000 hops per second [47].

¶ How Does Link-16 Work in Operations?

Link-16 transmits tactical information between all networked participants:

• Air picture: Positions of all detected friendly and hostile aircraft
• Target assignments: Which aircraft should engage which target
• Commands: Instructions from the ground command centre
• PPLI messages (Precise Participant Location and Identification): Each participant periodically transmits its own position, identity and status – a kind of network "heartbeat" [47]

¶ Why Does Link-16 Compromise Stealth?

Link-16 uses omnidirectional antennas – signals are broadcast in all directions simultaneously (360°). This is operationally necessary because the positions of communication partners change constantly during dynamic air combat. The consequences for stealth are severe:

1. High transmit power: Link-16 terminals (MIDS-LVT) transmit at up to 200 watts. This energy propagates almost unimpeded through the atmosphere in the L-band [47].

2. Detectability by adversary systems: Passive surveillance systems such as the Czech VERA-NG can detect Link-16 emissions at ranges of over 230 km. The physical limit, depending on flight altitude, is 400 to 600 km – far beyond the aircraft's own weapons range [45] [43].

3. Automatic PPLI transmissions: Even if a pilot consciously refrains from sending tactical messages, the Link-16 terminal continues to transmit periodic position reports (PPLI) in the background for network synchronisation. These regular transmissions form a constant "heartbeat" that immediately reveals the presence of a Link-16 network [47].

4. Precise location via Time Difference of Arrival (TDOA): Systems like VERA-NG use several spatially distributed receiving stations that measure the time difference of the arriving signal. Through multilateration (similar to the GPS principle but in reverse), the transmitter's position can be determined to within 100 metres – passively, without emitting any signals [45].

¶ The Dilemma for Switzerland

The Swiss F-35 fleet requires Link-16 for operational command and control, as the connection to Swiss ground stations and air defence centres necessarily runs via Link-16. Without this link to the ground command, no situational picture can be transmitted to the F-35 – the aircraft would be limited to its own sensors. Yet every use of Link-16 negates the stealth characteristics of the F-35, as adversary EW systems can determine the aircraft's position from hundreds of kilometres away.

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¶ SATCOM: The Connection Beyond the Horizon

¶ What is SATCOM?

SATCOM (Satellite Communication) enables communication via geostationary or low-orbiting military satellites. This allows an F-35 to communicate with command centres even when no direct line of sight exists – for example during operations far from home territory or behind mountain ranges.

¶ Why is SATCOM Critical for Stealth Operations?

SATCOM solves the central problem of Link-16: the F-35 can relay its data via a satellite to ground stations without having to transmit omnidirectionally. The satellite antennas direct their beam upward – away from adversaries on the ground or at low altitude. This makes SATCOM a prerequisite for the F-35 to operate in stealth while simultaneously maintaining a connection to ground command.

¶ Current Status

The full SATCOM capability of the F-35 (Block 4, codenamed "Digger-2") is delayed until at least 2031 – over ten years later than originally planned [43]. Until then, Link-16 remains the primary system for air-to-ground communication.

For Switzerland, there is an additional problem: the F-35 has fully functional AEHF terminals (Advanced Extremely High Frequency) for protected US military satellites, but as a non-NATO country Switzerland has no access to this satellite system [44]. European alternatives such as Syracuse IV (France), Skynet (United Kingdom) or the planned IRIS² programme of the EU would be technically compatible but require bilateral agreements and additional investments [42].

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¶ The Necessity of Data Links to Ground Command

A central point often overlooked in public discussion: the F-35 absolutely requires a data link to ground command centres to realise its full potential.

¶ Why is the Ground Connection Indispensable?

• Situational picture: Ground stations (e.g. the Swiss FLORAKO radar system) capture the complete air picture – including areas beyond the F-35's sensor range. Without this data, the F-35 sees only what its own sensors detect (radar: approx. 250–400 km).
• Friend-or-foe identification: Reliable identification of aircraft requires cross-referencing with ground data and civilian air traffic control information.
• Command and control: Political and military decisions (mission orders, weapons release, rules of engagement) must be transmitted from the ground to the pilots.
• Coordination: Operating multiple F-35s together with ground forces and air defence requires centralised coordination.

¶ The Problem Without SATCOM

Without protected SATCOM, the Swiss F-35 fleet has only two options:

1. Use Link-16: Full connection to the ground, but stealth characteristics are compromised over the entire operational range.
2. Maintain radio silence (EMCON): Stealth is preserved, but the F-35 loses the connection to command and operates without a current situational picture from the ground.

Both options are unsatisfactory. Only a stealth-compatible SATCOM connection or MADL gateway infrastructure on the ground would resolve this dilemma [41] [42].

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¶ 8. Communications – MADL, Link-16, SATCOM

¶ MADL (Multifunction Advanced Data Link)

MADL is the stealth-optimized data link of the F-35, operating in the Ku-band with directional phased-array antennas [38]:

• LPI/LPD: Low Probability of Intercept/Detection through directional beam characteristics
• Data rate: Significantly higher than Link-16
• Limitation: Only usable between F-35s; incompatible with F-22 (IFDL) and legacy platforms

¶ Link-16

The standardized NATO data link for broad interoperability [39]:

• Omnidirectional (not stealth-optimized)
• Compatible with virtually all NATO platforms
• Lower data rate than MADL

¶ The Interoperability Problem

F-35 (MADL) and F-22 (IFDL) cannot communicate directly with each other [39]. Solution approaches:

• U-2S as Airborne Gateway: Demonstrated in 2021 – the U-2 translates between MADL, IFDL, and Link-16 [40]
• Open Systems Gateway (OSG): Tested at NATO Ramstein Flag 2025 – MADL-to-Keystone translation for ground artillery [41]
• DAGGR-2: Multi-protocol gateway with SATCOM integration (commercial via Starlink/Intelsat) [42]

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¶ References

[38] Wikipedia: Multifunction Advanced Data Link
[39] Air & Space Forces Magazine: The F-22 and the F-35 Are Struggling to Talk
[40] The War Zone: F-22 And F-35 Datalinks Finally Talk via U-2 Gateway. 2021
[41] Air & Space Forces Magazine: F-35 Cues Ground Artillery with New Data Gateway. 2025
[42] Bulgarian Military: Danish F-35 fighters test DAGGR-2. 2025
[43] GAO-25-107632: F-35 Joint Strike Fighter – Actions Needed to Address Late Deliveries and Other Challenges. 2025
[44] Congressional Research Service: F-35 Joint Strike Fighter (JSF) Program. 2024
[45] ERA a.s.: VERA-NG Passive Surveillance System – Technical Datasheet. 2024
[46] NATO Standardization Office: STANAG 5516 Ed 4 – Tactical Data Exchange – Link 16. 2008
[47] Defense Logistics Agency: MIL-STD-6016F – Tactical Data Link (TDL) 16 Message Standard. 2023