RSSI measured values for NRF52832

[Pradeep Chl]

I have an NRF52832 Receiver chipset board that detects a tag that is transmitting 10 bytes of payload every second.

I have an attenuator on the board before the antenna of the Receiver so that I can give required attenuation level.(gains).

I have gains of 0db, -4db, -8db, -12db, -16db, -20db, -24db and -28db. If I give a gain of 0db to the attenuator, I get a maximum distance of 20 meters. The tag gets detected in the 20 meter range. If I give a gain of -28db to the attenuator, I get a maximum distance of 3 meters.

For 0db gain, I am getting an RSSI value of 90 at 20 meters. For -28db gain, I am getting an RSSI value of 90 at 3 meters. For any gain I set at the attenuator, I am getting RSSI of about 90 at its maximum distance.

Why is the RSSI value dependent on the Gain of the attenuator?

I was under the impression that RSSI value will change as per the distance between the Receiver and the transmitter.

Rgds,

[Wojtek]

RSSI is not sent by transmitter (how would it know how far the receiver is?) - it is measured on the receiver. So, if you lower the gain by attenuator -> receiver measures power -> you get lower RSSI. As far as i know, nRF52 is sensitive for up to -96db (or something about that value), so you don't see packets with lower RSSI... Isn't that what attenuator is used for?

[awneil]

nRF52 is sensitive for up (sic?) to -96db

Or, perhaps it would be clearer to say that it's sensitive down to -96dB - below that, the receiver just can't "hear" it.

[Wojtek]

ah yes, you are completely right :)