iOS devices keep dropping Wifi connection - Apple Time Capsule

Hi All

I have the latest Apple Time Capsule with AC Wifi and I have an issue where are my iOS keep disconnecting from wifi for around 5 seconds before reconnecting. I have this this issue on my iPhone, iPad and Apple TV, it is most annoying on the apple tv as it stops be streaming anything from my iMac. It is not an issue with my iMac or Macbook.

Im sure its not distance related because the issue happens when my iPhone is on the same desk as the time capsule. does this sound like an issue with my time capsule or a fundamental issue with iOS 8 ?