Same place same time, CSI very different

[Statisticss]

Hi all,

In order to investigate the property of CSI, I have performed the following test:
I use 1 Tx, 2 Rx, all in monitor mode with a single antenna (rate 0x4101). I put the antenna of two Rx very close to each other (they are touching each other actually), and let Tx send several packets

Here are the figures of amplitude of CSI collected by two Rx:

It seems that they are really different from each other. Is this normal?