Short answer
An amplifier with very low added noise (typical NF 1–2.5 dB at L-band) placed as close to the antenna element as possible. Sets the cascaded noise figure of the entire receiver chain and lets the antenna drive long cable runs without C/N₀ loss.
Detailed explanation
Every modern GNSS antenna integrates an LNA directly behind the radiating element. The LNA boosts the weak satellite signal (~−128 dBm at the antenna for GPS L1 C/A) by 20–46 dB before it enters the coax cable run, where it would otherwise pick up cable loss and external noise.
Two LNA parameters drive system performance: gain (in dB, typically 20–46 for GNSS LNAs) and noise figure (NF, in dB, typically 1.0–2.5). The Friis cascade formula F_total = F_1 + (F_2 − 1) / G_1 + … shows that the noise figure of the FIRST stage (the antenna LNA) dominates everything downstream once its gain is large enough — which is why putting the LNA inside the antenna housing matters so much.
Cable selection follows from LNA gain: with a 46 dB antenna LNA, even 100 m of LMR-400 (≈ 6.5 dB loss at 1.575 GHz) is masked by the LNA gain and the cascade NF stays at ~2 dB. With a passive (no LNA) antenna, that same cable run would push cascade NF to 10+ dB and drop C/N₀ by 8 dB — the receiver might not maintain track.
GNSource antennas ship in 30 dB, 36 dB, and 46 dB gain variants matched to the typical cable lengths of their target platforms — short for UAV (5–10 m), long for CORS (100+ m). The high-gain variant isn't always worth the surcharge; the link-budget calculator on the tools section back-solves the right gain for your specific cable run.
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High-Precision GNSS Measurement
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RF Link Budget Calculator
Open the toolRelated terms
Phase center
The apparent electrical centre of an antenna — the point from which signal range is effectively measured by a GNSS receiver. Phase-centre stability (the variation in this point as the signal arrival angle changes) is the single most important parameter for survey-grade and geodetic antennas.
Patch antenna
A flat ceramic or PCB GNSS antenna with a single dielectric-loaded radiating element on a ground plane. The dominant antenna type for compact, low-cost, vehicle, and OEM applications — ranging from 18 × 18 mm pucks to 100 mm survey-grade discs.
Helical antenna
A coiled-wire GNSS antenna offering broader bandwidth than a patch in a similar footprint, naturally circularly polarised. Common in UAV / aviation applications where the form factor (10–30 mm diameter cylinder) fits drone arms or wing-mount sockets.