(V)SWR

To: tesla-at-poodle.pupman-dot-com
Subject: (V)SWR
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 18 Mar 1997 23:39:46 -0600
Approved: tesla-at-stic-dot-net
Subject: 
        (V)SWR
  Date: 
        Tue, 18 Mar 97 09:48:00 EST
  From: 
        pierson-at-gone.ENET.dec-dot-com
    To: 
       
mail11:;;;;;-at-us4rmc.pko.dec-dot-com-at-us4rmc.pko.dec-dot-com-at-digital-dot-com;;;;;;;;
(-at-teslatech)
    CC: 
        pierson-at-gone.ENET.dec-dot-com


>        I'm used to the term VSWR as used to show the mismatch on
>a transmission line of defined impedance.
        Thats the usual use.

        It can be applied anywhere, where energy is transferred [1]
between
        elements of a system.  Obvious locations in a 'tesla coil'
system:

        Tank to resonator.
        Feed of resonator top.

        Tank to resonator LOOKS Like 'one thing' the lines are short,
but
        there is an energy transfer.  It may be easiest to look at the
        resonator.  Consider it a 1/4 wave line.  Top is open.  Infinite
        Impedance (wellllll.  More or less.  Much Less once break out
gets
        serious...).

        This 'reflects' to a low impedance towards the base.  The tank
couples
        to this.  Now EXACTLY where and EXACTLY how determine the
impedance
        'seen' by the tank.

        Similarly, it is possible to have an arbitrarily large number of
        DIFFERENT tanks, each resonant at the same frequency.  Each will
have
        a particular characteristic impedance.  Matching THAT to the one
that
        shows up at the point where the tank couples to the secondary,
MAY
        optimize performance. [2]

>Can't figure out how to make any sense of of measuring the "VSWR" of an
>isolated device.
        VSWR discussion is MOST COMONLY ENCOUNTERED on transmission
lines.  It
        APPLIES anywhere energy is coupled.  [1]  Substitute the phrase
        'impedance matching'  (VSWR is a unit of impedance mismatch, to
a large
        extent.)

        One could consider the 'vswr' all the way from the wall plug,
thru the
        Power Supply to the tip of the resonator, in about 3 stages.

        Think of breaking the system out into its component pieces and
connect
        each by a transmission line.  Then take the transmission line to
zero
        length.  The impedance mismatches (if any) are still there.

>What are you all talking about???????????
        Tesla Coils.  8)>>

        In a very real sense, (IMO) the achieving of high voltages is an
        exercise in getting the VSWR of the resonator(and added bits, as
        toroids, etc) as high as possible.

        Put another way, vswr always involves two impedances.  If they
match
        vswr == 1.  If they don't, its something else.  VSWR involving
        a transmission line actually exists independently at both ends:
        one value at the source-tx line, one at tx-line to load.  If one
        puts the load at the source (usual tesla coil config) its the
tx-load
        mismatch, direct, if any, that matters. 

======================
[1]
        And i mean ANY system with energy transfer.  When water power
projects
        are designed the hydraulic 'transmission line' gets an
'impedance'
        calculation and protection agains mismatch installed. 
Ditto-ditto
        the 'pneumatic' transmission line inside a 'jet engine.  but i
digress.)

[2]
        It is common to discuss 'matched impedance== max energy
transer==
        good thing'.  Well Sometimes.  Actually, in many cases max
EFFICIENCY
        is more important and may or may not involve matched impedance.

=====================================
Thanks!
        to the admins for getting the 'cruft' off the top of the
messages...

        regards
        dwp