Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dan" <DUllfig@xxxxxxxxxxxxx>

Your contention that the current needs a two way path is, i believe, 
incorrect. That would be true for DC currents, but not AC. When the 
current is flowing from the tramsmitter to the receiver, the charge 
accumulates in the top capacitance of the receiver. When the current 
is flowing back, it flows back out of the reciver's capacitance, into 
the transmitters capacitance.

It is analogous to a hydraulic system, where instead of pumping the 
oil always in one direction (you need two hoses to do this), you kept 
pumping the oil back and forth. When you do that, you don't need a 
return hose, because the oil can go into an accumulator at each end. 
Think about it.

Dan

PS.: in common household AC, the neutral is not really a return path 
either, but a terminal to collect all three phases and add them 
together. By definition, being neutral, the neutral does not carry 
any current (beyond the untility pole, that is).


----- Original Message -----
From: <mailto:tesla@xxxxxxxxxx>Tesla list
To: <mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx
Sent: Sunday, September 11, 2005 8:31 PM
Subject: Re: Tesla Coil RF Transmitter

Original poster: Ed Phillips <<mailto:evp@xxxxxxxxxxx>evp@xxxxxxxxxxx>

"Hi all, this response isn't directed at any one in particular; I just
have a few observations:

1 -- the earth is conductive, or we would not be grounding equipment in
it;
2 -- RF can be conducted thru a conductor, or coax would not exist.

and finally,

3 -- given the above statements, why is it so hard for anyone to
believe that Tesla was transmitting by conduction through the earth,
and not propagation through the air?! Just becuase you CAN transmit
RF through the air, doesn't mean it is the ONLY way to do it."

It is impossible to believe that transmission was solely through the
earth, as many seem to believe.  Take your example of a coax cable.  The
current flow is through the center conductor with a return path through
the inside of the outer conductor.  TWO-way circuit!!!  In Tesla's case,
at least as we interpret it now, the current was to flow into the earth
from the bottom of the coil.  Period.  No return path.  No way at all
this could work.  I wonder if Tesla is being misinterpreted and never
intended to say that there was no return path for the current carried
through the earth.  For sure his patents talk of a TWO conductor
transmission path, with one conductor being the ionized "upper layer"
and the other being the ground.  Always TWO conductors.  Just read the
patents.  When he speaks of "driving currents into the ground" that may
just be hyperbole.

"And Sam, you said the TC transmits poorly; considering that Tesla was
lighting up light bulbs with his receivers, seems his coils were
transmitting just fine..."

No foundation for that statement.  He did indeed light bulbs, probably
through inductive or capacitive coupling (unless you believe the stuff
about lighting many bulbs many miles a way, a statement with no proof at
all and apparently invented after his time).  However, he never even
mentioned how much power was transmitted or being wasted.  Probably most
of it was wasted.  Efficiency was probably nil.

"Some of his earlier experiments involved running a loop of cable
around his laboratory. He would run RF through it, and light up
special bulbs anywhere in his lab. He was constantly running
experiments, probably hundreds of them by the time he was through. If
his transmitters acutally needed an Aerial, don't you think he would
have figured that out? why would he drop the earlier aerial (say that
really quick three times :) in favor of a capacitive top load, if it
performed worse? It's not like he never tried an antenna!"

That was simple inductive coupling and not transmission.  No mystery,
no miracle, no significant technical accomplishment except for the high
frequency involved and his method of generating it.  You can do it just
as well as he did and the results will be just as good.

Ed