nRF52840 transmission power limit & regulations

Question

Hi, 
 What is an optimal transmission power to maximize the coded PHY range, but still stay within ETSI regulations? Can nRF52840 actually exceed the regulations if I set the transmission power accidentally too high? Currently, I have set it 8.

Jørn · Accepted Answer

Hello slowhand 
 From what I can see in ETSI EN 300 328 V2.1.1, ETSI sets an upper limit for non-adaptive equipment using Frequency hopping spread spectrum of 20dBm EIRP (100mW). 
 That is, with output power from the chip and gain from antenna combined. The nRF52840 can achieve a maximum of 8dBm, and its antennas have close to 0 dBi gain, meaning even with the output power set to maximum you should be well below the limit set by ETSI. 
 EDIT: 
 Your comment got me thinking and I conferred with a colleague. ETSI does in fact not define BLE as FHSS but as Direct Spread Spectrum (DSSS) due to the advertising channels, so it goes under the "other wide band modulation" section. The maximum output power is still the same for non-adaptive equipment, 20 dBm EIRP, but there is an additional power spectral density requirement as you said of 10mW/MHz. If I'm not completely off here, as each channel in BLE is 2MHz wide the nRF52840 should still be well within the specifications. 
 The Bluetooth 4.2 specification limits the output power to 10 dBm, and our previous chips had 4dBm maximum output power. In Bluetooth 5 that limit is raised to 20 dBm, and the nRF52840 is the first chip with 8dBm output power. 
 Best regards 
 Jørn Frøysa