rssi scan channel

Dear Dialog,

我想知道关于DA14580后点central operation mode.

Q1: We observed that rssi seems to have strong dependancy to the scanning channel. When we set 5seconds
for scan interval, we saw 5 seconds'periodic change of rssi by almost 10 - 15dBm change even the distance
of central and peripheral is fixed and experiment is conducted in the shield room.
Can you explain this phenomenon?
We have checked there is only a very slight varience like 1dBm for peripheral's transmit power.