How can I measure a wall attenuation

Hello all.
Im measuring a wall attenuation on 770MHz & 2.401GHz and Im using
But there is odd situation.
The noise floor of 770Mhz was -110dB and I calibrated 2.401GHz to make
its noise floor be the same with 770MHz. and I made both signal had the
same peak when I transmitted the signal in LOS.
As a result both signal had the same noise floor and same peak

The peak amplitude of 2.401GHz, however, was higher then 770MHz when
there was a wall!!. Its peak amplitude was higher about 10dB. I dont understand this situation.
As far as I know, the signal of 770MHz is more penetrate a obstacles.
How can I explain this situation??

I guess this situation was happen due to two things.

  1. I was wrong to calibrate the signals.
  2. The 2.401GHz antenna has better performance.

That`s the only thing I can guess.
Please help me anybody.