Wifi Dropping Every 20 mins - changed every piece of equipment

I had issues with my Wifi in my house for about a year now. Basically every device connected to my wifi network looses connectivity about every 20 minutes, the connection will drop for about 2 minutes and then come back up. During that 2 minutes if I connect my PC to the router with a ethernet cable the internet connection is live. Ive changed my router multiple times, ive changed the location of my modem and router, ive changed which wifi channels i use, ive even changed ISPs I went from DSL to cable but sill the problem persists. I looked at my router setting and I dont see anything wrong with it, the IP lease time is 1 week. I have two cordless phones in my house 1 at 900 Mhz and 1 at 6GHz but I havent found any correlation between phone usage and wifi droppage. Any ideas, this is driving me nuts?