nRF52840 - Unreliable RSSI

RE: nRF52840 - Unreliable RSSI

Håkon Alseth — Tue, 05 May 2026 13:48:51 GMT

Hi,

It is expected that RSSI varies when measuring radiated.

[quote user="igor.gorjanc"]Can we do anything to minimize this RX RSSI variability of the nRF?[/quote]

Just to avoid any confusion here:

It is not from the nRF radio itself, it is due to reflections and other physical parameters, as listed in the initial link.

If you connect a coaxial cable between the transmitter and receiver, and place it in a shielded box; you will get accurate measurements.

Kind regards,

Håkon

RE: nRF52840 - Unreliable RSSI

Igor — Tue, 05 May 2026 13:20:49 GMT

The spectrum analyzer is connected to RX antenna, i.e. signal goes through the air.
TX - RX air distance is cca 30 cm in the test setup (in practice it will be meters).
Can we do anything to minimize this RX RSSI variability of the nRF?

RE: nRF52840 - Unreliable RSSI

Håkon Alseth — Tue, 05 May 2026 12:44:57 GMT

Hi,

Can you please confirm how you are measuring the RSSI?

If it is conducted, ie. connected via a coaxial cable, then you should see little variation.

If radiated, ie. antenna to antenna, you will see high variation.

Kind regards,

Håkon

RE: nRF52840 - Unreliable RSSI

Igor — Tue, 05 May 2026 12:21:21 GMT

These measurements are done on RX side.

Please check the attached video of specral analyzer with lab-grade log-periodic RX antenna.

Despite having the same nRF transmitter, we are unable to replicate this RX variability with our lab-grade antenna.

So, the question remains, why do we get this RX RSSI variability? And mostly, what can we do to mitigate it?
devzone.nordicsemi.com/.../20260504_5F00_142601.mp4

RE: nRF52840 - Unreliable RSSI

Håkon Alseth — Tue, 05 May 2026 11:37:14 GMT

Hi,

[quote user=""]

Test hardware setup:
beacon GAP advertiser (stationary)
beacon GAP receiver (stationary) with filter for our beacons
both devices use the same nRF module.

[/quote]

Is this a radiated measurement?

If yes, then this is expected to vary. See other threads (search for "rssi radiated" or similar on this forum), for instance this:

RE: RSSI Instability: Seeking Insights on nrf52840

Kind regards,

Håkon