In matlab 2019b, the embedded USRP simulink block E3xx, the value of the gain of the Tx sems to have no effect.(too weak)

In E3xx simulink block, the valuable is tunable. However, I try to use a spectrum analyser to monitor the output of the Tx radio. It turns out that the signal strength is very low. I tried the 0db value. When I put the antennas of the TX and the spectrum analyser very close, the signal is about -40dbm, Which is near 0 dbm in the order version of simulink block of this type. There seems to be some mistake in the new released simulink block E3xx.