If the power light is a stable "white" then its not disconnecting from the network it is just your wifi connection to it that is dropping. To "prove" this can you connect a computer/laptop directly into the Hub on an ethernet cable and see whether that remains connected ok when the wifi devices drop out.
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.