[time-nuts] Thinking outside the box a super reference

[jimlux]

On 11/5/16 2:59 AM, Attila Kinali wrote:
  But we still need to ensure that the field is properly
> oriented and homogenous over the whole vapor cell. For this you need
> a cavity that is properly designed and most likely will be resonant at 6.9GHz.
> (I don't know whether it is possible to design a non-resonant cavity with
> the above properties)

isn't a TEM cell, as used in EMI/EMC testing, something like this?  It's 
a tapered transmission line and produces a uniform field within an area 
inside the line.