RX Calibration below 100MHz

I am trying to demodulate a simple AM signal with center frequency of 30MHz using the LimeSuite API. I wanted to use the LMS_Calibrate method, hoping I would receive a cleaner signal. However, the method gives an error when the LO frequency is tuned below 100MHz. It says:

Rx calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain?)

Can someone help me on this issue? Is is really impossible to calibrate the RX channel below 100MHz?

Thank you.