Receiving Mode-S and ADS-B signals at 1090 MHz requires millimeter precision. The Coaxial Collinear (CoCo) antenna is the ideal cost-performance balance for L-band feeders.

📡 Specifiche Hardware & Parametri RF

Frequency: 1090 MHzGain: 5-8 dBiNF: < 1.5 dBSDR: RTL-SDR Blog V3/V4
Dettaglio operativo Guida Feeder: Ottimizzare l'Antenna Coassiale Collineare (CoCo) per i 1090 MHz
📸 Fotografia autentica da Wikimedia Commons: Guida Feeder: Ottimizzare l'Antenna Coassiale Collineare (CoCo) per i 1090 MHz

RF Architecture and Velocity Factor

The core of the CoCo antenna is the Velocity Factor (VF) calculation. For RG-6 (typical VF 0.82) or RG-213 (VF 0.66), the length of each 1/2 wave segment must be calculated as: L = (c / f) * VF / 2. A few millimeters error shifts resonance out of band, degrading the Signal-to-Noise Ratio (SNR).

Bandpass Filters: Cavity vs SAW

In urban environments, LTE/5G interference is critical. SAW filters are compact and cheap, but cavity filters offer superior selectivity and lower insertion loss, essential for maintaining a low system Noise Figure (NF).

LNA Preamplifiers and Bias-Tee

Using an LNA near the antenna, powered via Bias-Tee, compensates for feedline losses. Avoid saturating the SDR; a total gain of 15-20 dB is usually sufficient.

Parameter / ComponentOptimal Value / Description
Impedance50 Ohm
Downlead CableLMR-400 or RG-213
ConnectorsN-Type (weatherproofed)
💡 Pro-Tip Installazione: Always use self-amalgamating tape on external connectors to prevent galvanic corrosion.
“Precision in segment cutting defines the real antenna gain, not theory.”

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