我家裡的網路路由器裝在一樓,桌電在三樓,利用網卡接收訊號。我發現在白天時,一樓的大片鐵捲門一打開,網路訊號馬上就大幅減弱,到了晚上鐵門關閉後,訊號馬上就恢復正常,請問這是甚麼原因呢?

A possible explanation is the door/gate acts as a shield preventing the WiFi signal "leaking" to the streets, and bounced the signal within your home.

So when the door/gate has opened, the shield can no longer function.

訊號被分散的關係
基本上如果有樓層的話
建議考慮購買Mesh的無線分享器
挑選有三台的機型在各樓層放置一台為佳