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[Towertalk] SWR & Speed of Light?

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Subject: [Towertalk] SWR & Speed of Light?
From: (Michael Keane, K1MK)
Date: Thu, 26 Sep 2002 04:53:44 -0700 (PDT)
On Thu, 26 September 2002, "David Robbins" wrote:

> Sri, nothing here of any practical use.  This is just a way for
> to observe the phenomenon of phase velocity exceeding the speed of
> light.  No way to transfer energy or information any faster than light
> either in our out of the medium.
> David Robbins K1TTT

I'm with Dave, there's much less here than meets the eye.

It's a cute physics lab demo, but what it's doing is making use of
dispersion to do pulse shaping. The applied pulse width & shape is
selected so that in travelling down a series of alternating quarter wave
sections the pulse will get compressed. 

It's relative to the leading edge of the pulse, that the pulse peak
"propogates" at 3.7 x c. Both the leading edge and peak travel down the
line by an amount less than c given by the classical velocity factor.  

For those interested the reference to the peer reviewed paper is:

J. N. Munday and W. M. Robertson, "Negative group velocity pulse
tunneling through a coaxial photonic crystal", Applied Physics Letters, 
81(11) 2217-2129

Mike K1MK

Michael Keane K1MK
PeoplePC:  It's for people. And it's just smart. 

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