Re: [TCML] tuning a tesla coil for broadcast?

["Gary Peterson" <g.peterson@xxxxxxxxxxxx>]

> How were coils tuned for transmitting . . . ?

The basic Tesla coil design is the same whether it be used for the creation 
of artificial lightning or wireless energy transmission.

Spark gap tesla coils (SGTC) are partially damped or damped-wave 
oscillators, depending upon the break rate.  Electrical vibrations in the 
resonance transformer's secondary coil ring down partially or completely 
before the next primary pulse occurs, in contrast to an undamped or 
continuous wave (CW) oscillator.  An advantage of the solid state Tesla coil 
(SSTC) over the SGTC is that the break rate is easily increased up to the 
secondary's resonant frequency, allowing for CW operation.  Another 
advantage of the SSTC is ease of primary circuit tuning.  One doesn't have 
to make adjustments to the primary capacitor and a primary tap.  The exact 
same result is achieved by adjusting the function generator's pulse 
repetition frequency.  Furthermore, the possibility of spurious emissions in 
the form of electromagnetic radiation is reduced.

The procedure for modifying an SGTC for wireless transmission involves 
increasing the size of the topload terminal and raising it up slightly above 
the top turn of the secondary.  The next step is to increase the primary 
capacitance to slow down its rate of vibration and bring the primary circuit 
back into tune with the modified secondary-topload combination.  The idea is 
to create a high potential on the elevated terminal at the greatest break 
rate possible but with no sparks or streamers issuing forth.

The basic Tesla coil receiving apparatus used to receive the transmitted 
energy consists of a helical resonator connected at its top to an elevated 
terminal and at its bottom to a deep ground rod, just like the transmitter. 
This type of receiver might be called an active receiver in that it includes 
a local oscillator and regenerative circuitry.  The second form of the Tesla 
wireless receiver is passive.  It consists simply of a grounded top-loaded 
helical resonator with some arrangement for sensing the induced electric or 
magnetic field associated with the current flowing between the ground 
connection and elevated terminal through the helical resonator as a result 
of the received electrical energy.  The sensor is either an amplified 
E-field or H-field probe.  The H-field probe is in the form of a secondary 
coil close wound around the resonator primary, close to its base.  In place 
of the amplifier a small low-voltage incandescent lamp can be connected to 
the secondary as a load.  A small permanent magnet DC motor can be run 
through a 4-diode bridge rectifier.  Before going out into the field, work 
with this arrangement for a while to hone your tuning skills.

Once the transmitter and receiver are built and in place with elevated 
terminals and robust ground connections, close down the primary spark gap to 
increase the break rate, and adjust the transmitter's primary capacitor and 
the primary tap so that the primary vibration is the same as the secondary 
vibration.  The tuning objective is to develop the maximum e-field in the 
vicinity of the transmitter.  To measure the e-field use an analog voltmeter 
set on a lower AC volts scale with the COM terminal lead to an independent 
ground and a long V terminal lead supported up in the air as an e-field 
probe.  A fluorescent tube on a grounded stand also works fairly well.  The 
transmitter does not have to be powered up to the point where sparks are 
just about to break out.  When everything is properly tuned the transmission 
and reception takes place even at very low input levels.

Please visit http://www.tfcbooks.com/teslafaq/q&a_052.htm for important 
regulatory information, etc.

Regards,
Gary

Gary Peterson
P.O. Box 2001
Breckenridge, CO 80424-2001
g.peterson@xxxxxxxxxxxx
Phone: 970-453-9293
www.teslaradio.com


----- Original Message ----- 
From: "Tim Meehan" <btmeehan@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, November 16, 2007 11:21 PM
Subject: [TCML] tuning a tesla coil for broadcast?

> I don't want to broadcast - however - I think that earlier people were
> discussing the original idea of power broadcasting, the sparks we all 
> crave
> were a nuisance.  How were coils tuned for transmitting - or for lighting 
> up
> fluoresent tubes? 

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