nRF21540 difference between +10 dBm and +20 dBm mode when using with a cellphone

RE: nRF21540 difference between +10 dBm and +20 dBm mode when using with a cellphone

PaKa — Wed, 21 May 2025 13:59:11 GMT

Yes, you are adding 17dB for the link budget in one direction and only 3 in the other direction so you may get an asymetric link. Not sure what the max power on the phones are but they do use regional awareness so even if they support more then 10dBm they should not use it if testing in Europe.

RE: nRF21540 difference between +10 dBm and +20 dBm mode when using with a cellphone

puz_md — Wed, 21 May 2025 13:47:47 GMT

Thanks for your reply. As mentioned above, I'm setting Tx power correctly which can also be observed in the extended range for advertising (compared +20 dBm to +10 dBm and compared to the nRF5340 without FEM). My point is that increasing Tx power further will not improve bidirectional connection stability if the mobile phone still sends with its nominal power, probably below +10 dBm, which cannot overcome significantly more range then Nordic at +10 dBm to the mobile phone.

RE: nRF21540 difference between +10 dBm and +20 dBm mode when using with a cellphone

PaKa — Wed, 21 May 2025 13:20:41 GMT

I would check that you have set up the power correctly then to validate that you are actually changing the output power. Are you setting the antenna power in your code? Default for this is 0dBm.

Note: the 13dB gain in the LNA does not mean you get 13dB better link budget. The LNA brings the sensitivity up to around -100dBm. This is as the Noise Factor of the LNA must also be looked at.

RE: nRF21540 difference between +10 dBm and +20 dBm mode when using with a cellphone

puz_md — Wed, 21 May 2025 13:07:58 GMT

Hi Kenneth,

we could see the advertising from a greater distance when using +20 dBm, this should be the same effect as the beacon example you mentioned. Although this does not cover our usecase with bidirectional communication.

Anyway, thanks for the quick feedback!

Best regards,
Michael

RE: nRF21540 difference between +10 dBm and +20 dBm mode when using with a cellphone

Kenneth — Wed, 21 May 2025 10:49:37 GMT

Hello,

I am sorry to say, but don't have any experience with this in specific, but what you write do make sense.

Something you may try is to program the board with the beacon example (since that is transmit only), and check if there is a distance difference with +10dBm vs. +20dBm then (I would expect that).

Kenneth