Contents: Multi-band receivers

Benefits of a multi-band receiver
What are multiband receivers?
What’s special about L5
Two frequencies are good news
What about other GNSSs

Benefits of a multi-band receiver

• Removes atmospheric errors.
• Smaller multipath errors.
• More resistant to interference.
• Will perform better in tricky GPS environments.
• More reliable accuracy. ±2m in ideal conditions.

What are multi-band receivers?

This is relatively new technology for consumer devices. The first smartphone to launch with multi-band tech was the Xiaomi Mi 8 in 2018. As I write (2023) it’s readily available in smartphones, GNSS watches and hand helds. However it’s not standard in all devices. You generally have to pay a little more if you want a multi-band device.

This tech also gets called ‘multi-frequency’ or ‘dual-frequency’ or ‘dual-band’. Different labels for the same thing.

Until recently, the American GPS satellites broadcast data for civilian consumer units on a single frequency known as L1. The identical signals are now being transmitted for civilian use, by some satellites, on two frequencies at once. L1 and a second frequency called L5. If a consumer GPS receiver can process the data on both the L1 and L5 frequencies then it is a ‘multi-band’ receiver.

Currently not all the GPS satellites broadcast on two frequencies, but it’s anticipated that a full set of 24 will be available by 2024. The Chinese Beidou and EU’s Galileo GNSSs both offer dual-band tech too.

What’s special about L5?

To quote GPS.gov, it’s “designed to meet demanding requirements for safety-of-life transportation and other high-performance applications…it features higher power, greater bandwidth, and an advanced signal design.”

That ‘advanced signal design’ makes L5 a more robust signal than L1. It’s less affected by multipath errors or interference. Having two different frequencies carrying the same data also enables the GNSS receiver to calculate a more accurate location fix.

Two frequencies are good news

A great advantage of a multi-band receiver is it’s ability to work out the continuously varying atmospheric errors all by itself.

Just as different colours of light are refracted and delayed differently by a prism, L1 and L5 are refracted and delayed differently by the atmosphere.

This means that the identical data from a single satellite, sent at the same time on both L1 and L5, arrive at the receiver at different times. That difference in arrival time allows the receiver to work out the atmospheric delay and make more accurate calculations for position.

A multi-band unit will perform the same trick anywhere in the world without help from regional error-correcting SBAS signals like the EGNOS system we enjoy in Europe.

Two frequencies also help the receiver be more resistant to radio interference. If interference is swamping the GPS signals on one frequency then the receiver can use the other.

What about other GNSSs?

For consumer units, Galileo and Beidou offer similar dual-frequency capability to the American system. Both use the same two frequencies but they are known as E1 and E5a for the Galileo system, and for Beidou: B1 and B2a.

GNSS	Normal frequency (1575.42 MHz)	Extra frequency (1176.45 MHz)
GPS	L1	L5
Galileo	E1	E5a
Beidou	B1	B2a

A multi-band receiver might just process two frequencies from the American GPS or may use two frequencies from all three GNSSs. Checking the manufacturers tech specs of a GPS handheld or smartphone won’t necessarily reveal what it does, often this information is not published and some digging may be required to find out.

Some of the other frequencies used by the various satellite systems are encrypted and reserved for military use.

So, if you would like a GNSS receiver that is as accurate as possible, get a multi-band receiver. They are available in phones, handhelds and watches.