In the contemporary landscape of electronic warfare (EW), the Middle East has become an open-air laboratory for GNSS interference. This article explores how cooperative surveillance systems like ADS-B (Automatic Dependent Surveillance-Broadcast) can be used to identify and map spoofing and jamming attacks affecting civil aviation.
📡 Hardware Specs & RF Parameters
- Frequency: 1090 MHz (Mode-S) / 978 MHz (UAT)
- Antenna Gain: 5.5 - 9 dBi (Collinear)
- Noise Figure (NF): < 1.2 dB
- Recommended SDR: Airspy Mini or RTL-SDR V4
RF Architecture and the Mode-S Data Link
The ADS-B system operates on the 1090 MHz carrier frequency using Pulse Position Modulation (PPM). Unlike primary radars that calculate position via reflection, ADS-B transmits coordinates derived from the onboard GNSS receiver. When a GNSS signal is manipulated (spoofing), the aircraft broadcasts a false position. However, the discrepancy between the reported position and the position calculated via Multilateration (MLAT) by ground receivers allows the interference to be unmasked.
Bandpass Filters: Cavity vs SAW
In high-density RF signal environments or in the presence of intentional jamming, filter selection is critical. SAW (Surface Acoustic Wave) filters are inexpensive and compact but have significant insertion loss. In contrast, Cavity Filters offer a very high quality factor (Q) and superior out-of-band rejection, essential for protecting the SDR receiver front-end from saturation caused by nearby LTE transmitters or radars.
LNA Preamplifiers and Bias-Tee
Using a Low Noise Amplifier (LNA) positioned near the antenna is vital to compensate for coaxial cable losses. A system powered via Bias-Tee allows DC voltage to be sent to the LNA directly through the RF cable, optimizing the Signal-to-Noise Ratio (SNR). Gain calibration must be precise: excessive gain can raise the noise floor, making weak ADS-B messages from distant aircraft invisible.
| Parameter / Component | Optimal Value / Description |
|---|---|
| Bandpass Filter | 1090MHz Cavity (BW < 10MHz) |
| Coaxial Cable | LMR-400 or better for long runs |
| SDR Sampling | 12-20 MSPS for detailed pulse analysis |
| Data Analysis | Monitoring NIC and NACp parameters |
In conclusion, monitoring anomalies in Mode-S logs provides valuable telemetry for aviation safety. We invite all enthusiasts and professionals to view real-time flights on map.adsbitalia.it and contribute to the network by consulting the feeder guide at adsbitalia.it/it/feeding.html.
