Talked to Roger Shawyer


  • Machining coming along
  • Introduced Roger Shawyer of our work and he is going to run our machined cavity dimensions through his simulation software.

Although my last entry was a number of months ago, a few things have been getting done.  I have been enjoying my machinist training immensely and we have been learning how to make “O.D.” cuts or “Outside Dimension” cuts.  For example, here was our project from last weekend:

NAIT MAC302 Lab Object

This Saturday we are learning how to cut threads and then in MAC303, we are finally learning how to do ID cuts or inside dimensions.

I have also settled on my first simple test structure, a tube that should resonate in the TE0,1 mode at 6Ghz and have a Q of 25,000.:

Simple Round Aluminum Test Structure with two ports and a Q of 25K

It should be easy to create from a 3″ diameter 5″ long aluminum bar I can get from the local Metal Supermarket for $33.  The great thing about aluminum is that it is so soft that the inserts (the blade used to cut) for machining have almost negligible wear.

I also decided to cross that PONR or Point Of No Return and contacted Roger Shawyer directly.  We had an interesting conversation last week and I have point him to this blog.  We talked about the following:

  • Other universities have tried building cavities but ultimately failed where we have – their simulations don’t match actual results.
  • Chinese Results:
    • Have been one (of few?) to have reproduced results.
    • Yang Jung group have built actual cavities and have gotten results of 750mN using 3Kw power.
    • The work has gone black/military and moved to Beijing, no more papers are being published.
    • Yang Jung was “disappeared” for six months with the implication of instilling dogma.
    • No one outside of China has seen their cavity, although Shawyer did traveled there and given talks.
    • They rebuilt commercial simulation software which took 19 months in order to deal with the discontinuities of asymmetrical cavities.
  • A Big Obvious Enterpris-ING company is the US contractor Shawyer has been working with
  • Sounds like the trick to powering the cavity at the resonant frequency, is to tune the cavity to the magnetron after it has warmed up, and the because of reflection, the cavity will pull the magnetron frequency and lock it in.
  • A simply geometry will get the cavity into a Q of thousands, but some type of internal shaping is required to get Qs of tens of thousands and the reason is because of phase continuity or coherence has to be maintained.

I have posted a summary of everything mentioned in this blog on the Research Summary pages.