GNSS antenna guide: L1/L2/L5 bands, geodetic vs smart antennas and RTK
Key takeaways
- A GNSS antenna determines which signals a receiver can track, so a multi-band receiver needs a multi-band antenna.
- L1 plus L2 and L5 lets an RTK receiver fix ambiguities faster and work over longer baselines than single-frequency equipment.
- Active antennas include a low-noise amplifier powered through the coaxial cable; passive antennas do not.
- For RTK, phase centre stability and multipath rejection matter more than raw gain.
- Cable length, connector type and mounting affect performance as much as the antenna itself.
What is a GNSS antenna?
A GNSS antenna is the component that collects satellite navigation signals and converts them into an electrical signal for the receiver. Every GNSS receiver, from a phone to a geodetic base station, has one, either built in or connected by cable.
People often search for a GPS antenna, but GPS is only one constellation. A GNSS (global navigation satellite system) antenna is designed to receive several systems: GPS, GLONASS, Galileo, BeiDou, QZSS and regional systems such as NavIC. Our article on GNSS vs GPS explains the difference in detail.
Satellite signals arrive at the antenna extremely weak, well below the background noise level, and they are right-hand circularly polarised (RHCP). A survey antenna must therefore be RHCP, sensitive across the correct frequency bands, and as resistant as possible to reflected signals. In an active antenna, a low-noise amplifier (LNA) boosts the signal before it travels down the cable.
GNSS frequency bands: GPS L1, L2, L5 and beyond
Each constellation broadcasts on several frequencies, and an antenna can only pass the bands it was designed for. The main GNSS frequency bands used in surveying are:
| Band | Centre frequency (MHz) | Signals on this band |
|---|---|---|
| L1 / E1 / B1C | 1575.42 | GPS L1, Galileo E1, BeiDou B1C, QZSS L1 |
| B1I | 1561.098 | BeiDou B1I |
| G1 | About 1598–1606 | GLONASS L1 (FDMA) |
| B3I / E6 | 1268.52 / 1278.75 | BeiDou B3I, Galileo E6 |
| G2 | About 1242–1249 | GLONASS L2 (FDMA) |
| L2 | 1227.60 | GPS L2 |
| E5b / B2b | 1207.14 | Galileo E5b, BeiDou B2b |
| L5 / E5a / B2a | 1176.45 | GPS L5, Galileo E5a, BeiDou B2a, NavIC L5 |
In practice, antennas cover an upper band around 1559–1610 MHz and a lower band around 1164–1300 MHz. Some also pass the L-band range near 1525–1560 MHz used by satellite-delivered correction services.
Dual frequency GPS vs single frequency: why multi-band matters for RTK
A dual frequency GPS receiver tracks signals on two bands, typically GPS L1 and L2, and modern survey receivers add L5 and the equivalent bands of other constellations. Multi-band tracking is the main reason survey-grade RTK fixes quickly and reliably.
- Ionospheric correction – the ionosphere delays each frequency differently, so comparing two or more frequencies removes most of that error.
- Faster ambiguity resolution – extra frequencies allow combinations that help the receiver resolve carrier-phase ambiguities in seconds.
- Longer baselines – multi-band RTK stays reliable further from the base than single-frequency L1 RTK.
- Robustness – modern signals on L5/E5a have higher power and better resistance to multipath.
A cheap L1 GPS antenna limits a multi-band receiver to L1. For RTK, the antenna's bands must match the receiver's. See what is RTK GPS for how carrier-phase positioning works.
Active vs passive GPS antenna
An active GPS antenna contains a low-noise amplifier powered by DC voltage sent up the coaxial cable from the receiver; a passive antenna has no amplifier. The choice depends mainly on cable length.
| Feature | Active antenna | Passive antenna |
|---|---|---|
| Amplifier (LNA) | Yes, often around 25–40 dB gain | No |
| Power | Typically 3–5 V DC via the coax | None |
| Cable length | Several metres to tens of metres | Very short only |
| Typical use | Survey, base stations, vehicles, external GPS antenna installs | Antennas mounted directly on a circuit board or inside a device |
Almost every external antenna for GNSS RTK is active, because cable loss would otherwise degrade the already weak signal. Check that the receiver supplies the voltage the antenna needs and that the LNA gain suits the cable length: too little gain loses signal, too much can overload the receiver input.
GPS antenna types: patch, helical, geodetic and smart antennas
GPS antenna types range from small ceramic patches to large choke-ring designs. Size, phase stability and multipath rejection rise together.
Ceramic patch antenna
A ceramic patch antenna GPS module uses a flat ceramic element over a ground plane. It is compact and inexpensive, found in phones, trackers and automotive GPS antenna units, and usually covers one or two bands with modest phase stability.
Helical antenna
Quadrifilar helical antennas are small and light with good low-elevation reception, which suits handheld receivers and drones.
Geodetic and survey antennas
A GNSS survey antenna uses multi-feed or stacked elements, a large ground plane and careful design to keep the phase centre stable in every direction. Choke-ring antennas add concentric rings to suppress low-angle reflections and are used at reference stations.
Smart antenna
A smart antenna combines antenna and receiver in one housing, outputting positions rather than raw RF. It is popular on tractors and machines. Dual antenna GPS installations use two antennas to measure heading as well as position.
What makes a good RTK antenna?
A good RTK antenna delivers clean, stable carrier-phase measurements. Gain alone is not the deciding factor; the following properties matter more for high precision GPS antenna performance.
- Phase centre stability – the electrical phase centre should not move with satellite direction. Variations are described by phase centre offset (PCO) and phase centre variation (PCV), and calibrated values can be applied in processing.
- Multipath rejection – a good gain pattern and ground plane reduce signals reflected from the ground, vehicles and buildings.
- Axial ratio – a low axial ratio means good circular polarisation and better rejection of reflected, left-hand polarised signals.
- Out-of-band filtering – filters protect against interference from mobile networks and radios.
- Rugged housing – IP67 sealing and a standard 5/8" × 11 survey mount.
Always measure antenna height to the antenna reference point (ARP) and enter the correct antenna model, otherwise vertical results will be biased.
GPS antenna connectors, cables and wiring
The antenna connector, cable type and cable length all affect the signal reaching the receiver. Survey and machine installations commonly use TNC connectors on the antenna, SMA connectors on compact receivers and modules, and N-type on radio antennas.
Coaxial cable loses signal with length, and loss increases with frequency. Thin cable such as RG-58 typically loses roughly half a decibel or more per metre at GNSS frequencies, while thicker low-loss cable loses much less. Keep runs as short as practical and choose the cable before choosing the amplifier gain.
- Choose the mounting point – highest clear position, away from radio antennas and metal edges.
- Fit the antenna level on a rigid 5/8" mount or magnetic base.
- Route the cable without sharp bends or crushing, and add drip loops outdoors.
- Seal outdoor connectors with self-amalgamating tape.
- Check the receiver supplies antenna power and reports normal signal-to-noise values.
Geodetic vs smart antenna: which should you choose?
Choose a geodetic antenna for base stations, monitoring and any setup where a separate receiver is used; choose a smart antenna for vehicles and machines that need a simple, single-unit installation.
| Need | Recommended |
|---|---|
| Permanent or temporary RTK base | Geodetic multi-band antenna on a tripod or pillar |
| Tractor guidance and auto-steer | Smart antenna with integrated receiver |
| Custom device or OEM board | Compact active multi-band antenna |
The Mars Geosystems SA102 geodetic GNSS antenna tracks GPS, BDS, GLONASS, Galileo (E1, E5a, E5b, AltBOC), QZSS, SBAS and L-band, with 36 ± 2 dB LNA gain, a TNC connector and IP67 sealing. The S20 smart antenna integrates a 1408-channel receiver for vehicles. GNSS antenna price varies widely, from low-cost patches to geodetic models costing many times more; request a quote for current pricing.
Frequently asked questions
What is the difference between a GPS antenna and a GNSS antenna?
A GPS antenna may be designed only for the American GPS signals, often just L1. A GNSS antenna covers multiple constellations, including GPS, GLONASS, Galileo, BeiDou and QZSS, usually on several frequency bands. For survey and RTK work, a multi-constellation, multi-band GNSS antenna gives more satellites, faster fixes and better reliability.
What are the GPS L1, L2 and L5 frequencies?
GPS L1 is broadcast at 1575.42 MHz, L2 at 1227.60 MHz and L5 at 1176.45 MHz. L1 carries the original civil signal used by every GPS device. L2 and L5 add frequencies that let survey receivers remove ionospheric error and resolve RTK ambiguities faster. L5 is a modern, higher-power signal designed for safety-of-life use.
Do I need an active GPS antenna?
If the antenna is connected through a cable longer than a few centimetres, an active antenna is almost always needed. Its built-in low-noise amplifier compensates for cable loss and keeps the signal-to-noise ratio high. Passive antennas are used mainly when the antenna sits directly on the receiver's circuit board.
Can I use any GPS antenna for RTK?
No. RTK needs an antenna that covers the same frequency bands as the receiver, has a stable phase centre and rejects multipath well. A low-cost single-band patch will limit a multi-band receiver and can cause slow or unreliable fixes. Use a multi-band survey, geodetic or high-quality RTK antenna instead.
What connector do GNSS antennas use?
Survey and geodetic GNSS antennas commonly use a TNC female connector, which is robust and weather resistant. Compact antennas and OEM modules often use SMA, while radio datalink antennas typically use N-type or TNC. Adapters exist, but each one adds a small loss, so matching connectors and cable from the start is better.
How high should a GNSS base antenna be mounted?
Mount a base antenna where it has a clear view of the sky above about 10–15 degrees elevation, away from walls, vehicles, fences and radio transmitters. A tripod at around 1.5–2 m over a known mark is common for temporary bases. Permanent stations are usually placed on a stable roof pillar or mast.
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