Bluetooth signal vs voltage level

[Ceranthor]

Hi.

i want to power my nrf52840 with 2 AAA batteries i connected them directly to the module. Is there any Bluetooth signal strength difference when battery voltage drop from 3 to 2.4 V for example?  Is there need for DC/DC booster to increase the voltage to 3.3 V? 

 

                                                                                   

[Kenneth]

Hello,

There is no difference in radio peformance due to supply voltage no. You can assume that all electrical parameters are the same over the entire supply range and temperature range.

Kenneth

[Ceranthor]

Hmmm thats interesting couse i saw the difference on 2 same boards with the same code set_tx_power on 8 on connection role (central and peripheral the same set_tx_power) and on new batteries have better signal strength. 

[Kenneth]

Are you sure you are measuring conducted and not radiated? What difference do you see? Can you repeat again?

Kenneth

[Ceranthor]

I measure RSSI in distance i have central node connected to the computer and a tripod about 3 m from the central. With 3V i have about 70 dbm and with lower (2.4 V) i have about 80 dbm. Same testing conditions. 

[Kenneth]

It's not possible to do this kind of testing radiated, and RSSI is not accurate enough, there are just to many unknowns in this kind of environment (e.g rssi is affected by reflections, orientation, obstacles, frequency, fading, and possible the presence of other carriers at the time the measurement is conducted). You should do this kind of measurement conducted and with a spectrum analyzer.

Kenneth