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Adalm Pluto SDR - Second RX channel signal issues

Category: Hardware

I have a Pluto SDR rev c, on which I just enable the second TX and RX channel. I am sending a simple sinusoidal signal at a specific frequency (fc), but different phase and amplitude, using the two TX channels. I am receiving the signal on the RX channel 1, and hence I am viewing it using the "QT GUI Frequency Sink" in GNU Radio.

However, when I try to use the second channel - RX2, instead of RX1, I get different results.

The gain of the signal has reduced on RX2 (-76.4 dBm), while I was expecting to see the same gain as RX1 (-59.14 dBm). I tried to change the phase of the TX Signal, but there is not much difference.

So my question is why am I seeing different results?