Certification test at 8dBm

[bonnet]

Hello

  Most of the time we shall use the BT TX 0dBm. In special cases when we want to increase the communication distance we may select the 8dBm mode.

For RF type approval test, should we perform the tests at 0 or 8dBm ?

Is there a risk to have spurious only at 8dBm ?

If we perform the tests only at 8dBm do we cover the spectrum at 0dBm ?

What is your recommendation ?

Thank you

[WestCoastDaz]

bonnetIt's best to test at the maximum power because you can easily turn it down after you have your certification without any retesting. The  FCC/CE tests record the maximum transmit power used during testing so you can't legally increase the output power past what was tested.  We always test our devices at +4dBm (we are using the nRF52832 at the moment) and we haven't had any issues with spurious emissions but in the end it comes down to the design.

[haakonsh]

To expand on Darren's answer:

There's a risk of harmonics at +8dBm. You need to send us your design files for review, and samples for precompliance testing and tuning of the harmonics filter. At +8dBm it is especially important to copy the reference design exactly. 

[bonnet]

Thank you for the answers. The design is not finished but we can provide you the RF schematic.

Next week we shall test at 0dBm in RF lab. If we see problem with this setting, we shall inform you.

Is the +4dBm mode less risky than the 8dBm concerning the spurious emissions ?

[haakonsh]

Yes, it is near identical to the nRF52832 at +4dBm and it does not have problems with harmonics. 
That being said it should not be problematic to tune the harmonics filter of the 52840 to certifiable levels given a good pcb layout.