Heavy radio test channel output power variation (nrf52840 DK)

RE: Heavy radio test channel output power variation (nrf52840 DK)

ChiragBhavsar — Thu, 16 May 2024 10:51:14 GMT

Hi,

I face same problem so this can effect on FCC Certificate?

RE: Heavy radio test channel output power variation (nrf52840 DK)

stivberb — Wed, 17 Nov 2021 16:50:55 GMT

I don't believe that is the case. When I switched modes and just manually changed the frequency I was getting similar results. I tried to connect an antenna to my device, giving me readings of around -12 dBm for channels 2 and 39. but -10 dBm on channel 78. No matter the settings I change, I seem to consistently see about a 2 dBm difference between the high end of the spectrum and the rest of the spectrum. Furthermore, channel 40 is still behaving absurdly as I am consistently getting readings much lower than the rest of the channels (around -37 dBm with the antenna).

RE: Heavy radio test channel output power variation (nrf52840 DK)

ketiljo — Wed, 17 Nov 2021 11:34:39 GMT

I don't have any experience with this instrument so I can't help you there. 7 dBm sounds about right. but 13.4 dBm is impossible so the instrument is doing something here.

Can it be that it's expecting a BLE formatted package? It's still strange that it measures this much.

RE: Heavy radio test channel output power variation (nrf52840 DK)

stivberb — Tue, 16 Nov 2021 15:01:52 GMT

Of course. After doing some more testing it seems the internal attenuator is the culprit, with it being set to auto I am getting readings around 13 dBm for channel 78 (on modulated tx carrier mode). However, when I set the attenuator to 0dBm I get more reasonable measurements of around 7dBm.

My only problem is that this causes my measurements at lower frequencies to be much smaller than expected. Is this expected or am I not using the proper settings with my spectrum analyzer? Should I be manually changing the attenuator based on the frequency/channel I am measuring?

Thanks again for your help.

RE: Heavy radio test channel output power variation (nrf52840 DK)

ketiljo — Tue, 16 Nov 2021 08:58:58 GMT

Something is seriously wrong here, you should see very little difference between the channels. 12.2 dBm is not possible. Can you post screenshots of the measurements?