In the MAX2769B Configuration 3 register, bits 13 and 12 enable the I and Q Programmable Gain Amplifiers (PGA), respectively. These bits are marked "reserved" in Table 9 of the datasheet.
A value of 1 enables the PGA, and 0 disables it. It can be seen that the default values of bits[13:12] = 10.
This will cause the I PGA to be enabled, but the Q PGA will be disabled. Hence no data will be output on the Q
pins using the default register values. To enable the Q output, write a "1" to bit 12.