WSPR with low power
For WSPR with low power, I advise to use an attenuation of 10 dB or 20 dB. An Attenuation of 3 dB is too small with WSPR. With 3 dB you will not notice any difference.
Because WSPR transmits for 2 minutes, I advise not to use more input power, than the nominal power of the first section that is in use.
Tip: Switch ON the sections of 1 dB, 2 dB and 7 dB to get an attenuation of 10 dB.
The sections of 1 dB, 2 dB, 7 dB and 10 dB will give 20 dB.
With the sections of 1 dB and 2 dB in front, the nominal power will be 2 watt. (Not 3 watt because the sections are consecutive.)