SNR for DVB-T(ET8000)

root@et8000:~# cat /proc/bus/nim_sockets
NIM Socket 0:
        Type: DVB-T2
        Name: Si216x
        Has_Outputs: yes
        Frontend_Device: 0
        I2C_Device: 3

The greatest  SNR Si216x(DVB-T2) of 55%.
At the same time USB DVB-T AVerMedia(A835) SNR 99%.

If SNR Si216x(DVB-T2) = 52%, AVerMedia(A835) SNR =  96%.

What could be the problem?