This is measurements of output device RMS voltage -> power for firmware "firmware_gain_516086.tar.gz". Other firmware's values may be different.

+-----------+------+--------+-----------+
| Amplitude | Vrms |  P dBm | P watt    |
+-----------+------+--------+-----------+
|   2.0     | 2.46 |  20.83 |  0.121    |
|   1.9     | 2.40 |  20.61 |  0.115    |
|   1.8     | 2.35 |  20.43 |  0.110    |
|   1.7     | 2.30 |  20.24 |  0.105    |
|   1.6     | 2.23 |  19.98 |  0.100    |
|   1.5     | 2.17 |  19.74 |  0.094    |
|   1.4     | 2.10 |  19.45 |  0.088    |
|   1.3     | 2.03 |  19.16 |  0.082    |
|   1.2     | 1.90 |  18.59 |  0.072    |
|   1.1     | 1.80 |  18.12 |  0.065    |
|   1.0     | 1.66 |  17.41 |  0.055    |
|   0.9     | 1.49 |  16.47 |  0.044    |
|   0.8     | 1.29 |  15.22 |  0.033    |
|   0.7     | 1.09 |  13.76 |  0.024    |
|   0.6     | 0.88 |  11.90 |  0.015    |
|   0.5     | 0.65 |   9.27 |  0.0085   |
|   0.4     | 0.42 |   5.48 |  0.0035   |
|   0.3     | 0.21 |  -0.55 |  0.00088  |
|   0.2     | 0.07 | -10.09 |  0.00009  |
|   0.1     | 0.01 | -26.99 |  0.000002 |
+-----------+------+--------+-----------+

Note: AD9957 DAC needs heatsink/radiator. If it's overheating, the output power may be decreased.