What determines range

The main influences

• Line of sight: LoRa at 868 MHz passes through walls and foliage, but every obstacle costs attenuation. With a clear view many kilometres are possible; in a street canyon often only a few hundred metres.
• Height: a gateway on a roof or a hill reaches much further than one on the ground floor. For the device, too, one metre of height often makes a difference.
• Buildings and basements: concrete, metal and coated windows attenuate strongly. For measurements in a basement (e.g. water meters) expect a loss of 20 to 30 dB.
• Antenna: a good antenna in the right place gains more than a higher spreading factor. Metal close to the antenna worsens reception.
• Body: if you hold the tester close to your body, the signal drops by a few dB. For comparable measurements always hold the tester the same way.

Fresnel zone

The radio wave needs free space around the direct line, the Fresnel zone. At 868 MHz its radius is about 20 m in the middle of a 5 km link. A hill or building just below the line of sight still attenuates the signal. As a rule of thumb at least 60 % of the zone should be clear.

Why survey with a field tester

Planning tools and maps give an estimate. Whether a sensor actually gets through at the planned spot only shows in a measurement on site.

With a LoRaWAN field tester and fieldtester.io you check RSSI, SNR, packet loss and the number of gateways at every point. It is best to measure with the spreading factor the sensor will later use, and at the spot where it will later be mounted.