Multi-Band GNSS: Why L1 + L5 Matters and What It Demands of the Antenna
For two decades, mass-market positioning meant one signal: GPS L1. Today, low-cost receiver chipsets track two or even three frequencies across four constellations, and metre-level or better accuracy is reaching asset trackers, drones, agricultural machines and delivery robots. The antenna, however, is often still chosen as if nothing had changed β and a single-band antenna on a dual-band receiver quietly throws the benefit away.
The signals
All four global constellations now broadcast open civil signals in two main regions of the L-band: an upper band around 1560β1610 MHz and a lower band around 1165β1300 MHz.
| Band | Centre frequency | Constellation / signal |
|---|---|---|
| Upper L-band | 1575.42 MHz | GPS L1, Galileo E1, BeiDou B1C |
| Upper L-band | 1561.098 MHz | BeiDou B1I |
| Upper L-band | 1598β1606 MHz | GLONASS L1 (FDMA) |
| Lower L-band | 1227.60 MHz | GPS L2 |
| Lower L-band | 1207.14 MHz | Galileo E5b, BeiDou B2b |
| Lower L-band | 1176.45 MHz | GPS L5, Galileo E5a, BeiDou B2a |
Notice that 1575.42 MHz and 1176.45 MHz are each shared by GPS, Galileo and BeiDou. This is why L1 + L5 has become the standard pairing for new dual-band designs: two frequencies give access to the modern signals of three constellations at once. L2 remains important for surveying and for existing professional equipment.
What the second frequency buys you
- Ionospheric correction. The ionosphere delays GNSS signals by an amount that depends on frequency (proportional to 1/fΒ²), and this is typically the largest single error for a single-frequency receiver. Measuring the same satellite on two frequencies lets the receiver calculate and remove the first-order delay, instead of relying on a broadcast model.
- Better multipath resistance. L5 and E5a use a chipping rate of 10.23 Mcps β ten times that of the L1 C/A code. The sharper correlation peak makes it much easier to separate the direct signal from reflections off buildings, which is the dominant problem in cities.
- A stronger, protected signal. L5 is transmitted at higher power than L1 C/A and lies in a band reserved for aeronautical radionavigation, giving it extra protection from interference.
- Faster, more reliable high-precision fixes. For RTK and PPP, dual-frequency measurements dramatically shorten the time needed to resolve carrier-phase ambiguities and make the solution more robust over longer baselines.
What it demands of the antenna
The upper and lower bands are about 400 MHz apart. A conventional single-feed ceramic patch for L1 has a usable bandwidth of only a few tens of MHz, so it simply does not respond at 1176 MHz. A multi-band GNSS antenna needs a different radiating structure β typically stacked patches, a wideband patch with multiple feeds, or a helical element β and a carefully designed active stage. When you compare multi-band antennas, look at the following.
- Gain in every band, not just L1. Check the zenith gain (in dBic) stated separately for the lower and upper bands; it is normal for the lower band to be somewhat weaker, but it must be specified.
- Polarization and axial ratio. GNSS signals are right-hand circularly polarised (RHCP). A reflection flips the polarization to left-hand, so an antenna with good circular polarization β a low axial ratio β rejects reflected signals by design. This multipath rejection should hold in both bands.
- LNA noise figure and gain. In an active antenna the first amplifier largely sets the noise figure of the whole receive chain, so lower is better. LNA gain (commonly 25β30 dB) must be enough to overcome the loss of your cable run without overloading the receiver input.
- Filtering and out-of-band rejection. When the antenna sits next to a cellular modem, strong LTE transmissions can desensitise the GNSS LNA; for example, the second harmonic of LTE Band 13 uplink (777β787 MHz) falls at 1554β1574 MHz, right beside L1. Good pre-filtering ahead of the LNA is what keeps a tracker working while it transmits.
- Phase centre stability. For RTK-grade work, the point from which the antenna appears to receive should stay stable across elevation, azimuth and frequency. It matters much less for metre-level tracking.
- Ground plane and mounting. Patch antennas are tuned with a particular ground plane in mind; magnetic or screw mounting on a metal surface generally improves gain toward the sky and reduces pickup of reflections from below. Give the antenna a clear view of the sky, away from other transmit antennas.
Do you need multi-band?
| Application | Typical requirement | Recommendation |
|---|---|---|
| Basic asset or fleet tracking, timing | Several metres | Single-band L1 multi-constellation is usually sufficient and lowest cost. |
| Urban tracking, micromobility, lane-level navigation | About a metre, robust among tall buildings | L1 + L5 gives a clear benefit through multipath resistance. |
| Drones, precision agriculture, machine control, surveying | Decimetre to centimetre (RTK / PPP) | Multi-band (L1 + L2 and/or L5) with a low-axial-ratio, stable-phase-centre antenna. |
Whichever you choose, the antenna and the receiver must match: a multi-band receiver connected to an L1-only antenna behaves as an L1-only receiver.
From our range
- GNB-55 β high-sensitivity, low-profile active antenna covering GPS L1 / L2 / L5, BeiDou B1 and GLONASS L1, with built-in LNA and filtering
- All GNSS / GPS antennas
- Combo antennas β GNSS together with LTE / 5G and Wi-Fi in one housing
- GNSS 101: General Knowledge About Global Positioning Systems
Need a GNSS antenna matched to a specific receiver module, cable length or enclosure? Our engineers can recommend a standard part or tune a custom design.