RSA-SDR-Dongle with DVK-SFEU-1-GEVK

Hi everyone,

I am trying to check a board with a Wisol module for RC1 (Sigfox Verified), but I don't know if the design is right or not. So I want to learn the way of checking these kinds of boards. I think the best option is to use an evaluation board, for example, this one by On Semiconductor DVK-SFEU-1-GEVK. (This board is 0U class.)

I have set the EVB in SFX_TEST_MODE_TX_CW mode, with a Tx power of 14 dB and a Tx frequency of 816.13MHz (Requirements for Sigfox Ready RC1). I am using the API, so these are the commands:

ONSEMI_set_tx_center_freq(868130000); -> Set Tx Frequency to 868.13 MHz

ONSEMI_set_tx_power(14); -> Set Tx Frequency to 14 dBm

err = ONSEMI_test_mode(SFX_TEST_MODE_TX_CW, 0); -> Continuous Wave Mode

And I am using the RSA-SDR-Dongle in order to measure the Tx power, and I can see things that they can be a little bit confused:

On the one hand, you can see that the Band Power is around -24.6 dBm + 40 dB (att) = 15.4 dBm that ii matches with the expected power, but on the other hand you can see two peaks on of them is -30 dBm + 40 dBm (att) = 10 dBm.

Questions:

1º. I don't know which is the right Tx power: 15.4 dBm or 10 dBm

2º. If my device is Tx to 868.13 MHz@14dBm why do we can see the peak move to the right at the 0 frequency (Hz)? and why do we can see two peaks?

Best regards.