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Re: indication of good tuning (fwd)
---------- Forwarded message ----------
Date: Sat, 4 Aug 2007 08:07:27 -0600
From: Gary Peterson <g.peterson@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: indication of good tuning (fwd)
It is important to keep in mind that spark-gap Tesla coils (SGTC) are
partially damped or damped-wave oscillators, depending upon the break rate.
This means that the electrical vibrations in the resonance transformer's
secondary coil ring down partially or completely before the next primary
pulse occurs. This is in contrast to an undamped or continuous wave (CW)
oscillator. The faster the break rate the faster the primary pulses, and
the closer one comes to achieving continuous wave operation. A significant
advantage to the solid state Tesla coil (SSTC) (and the vacuum tube Tesla
coil (VTTC) as well) over the SGTC is that the break rate is easily brought
up to the secondary's resonant frequency, allowing for continuous wave (CW)
operation. This is preferable if one is interested in investigating Tesla's
non-radiating form of wireless energy transmission. Another advantage of
the SSTC is the ease of primary circuit tuning. One doesn't have to fiddle
around making adjustments to the primary capacitor and a primary tap. The
exact same result is achieved by a simple adjustment of the function
generator's pulse repetition frequency. Furthermore, the possibility of
spurious emission in the form of electromagnetic radiation is greatly
reduced.
The procedure for modifying a Tesla coil 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 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.
When I was on the Board of Directors of the International Tesla Society in
1990 I did improvised a damped-wave Tesla coil RF transmitter. It was based
upon a fellow board member's tabletop TC display unit. The approximately 1"
knob topload was replaced with a copper flush-valve float, and moved off of
the secondary on to an improvised insulated stand a few inches higher than
its original position and a little bit off to the side. I modified its
glass-plate capacitor by adding another sheet of aluminum foil. The
receiving transformer, prepared beforehand, had an AWG 30 gauge primary
wound on a 1.75" cardboard tube. The secondary to which the load was
connected was wound on top of the helical-resonator primary towards the
lower end of the single-layer coil in exactly the same fashion as Tesla did
when he was in Colorado Springs in 1899. The load consisted of a 6-volt
pilot light. The elevated terminal was a sheet of aluminum foil hung off of
another improvised stand made of wooden sticks. The lamp was brightly lit
at a range of about 15 feet. It's not at all hard to do.
www.tfcbooks.com/teslafaq/000_0339-1_small.jpg This is a solid state Tesla
coil transmitter with an elevated terminal. The resonator has a 7:1 aspect
ratio, which is the same as one of the experimental coil forms that Tesla
used in Colorado Springs. The primary coil form or spool is the upper
portion of a 5-gallon plastic pail. The secondary or helical resonator coil
form was fabricated from a 1/8" thick cardboard cylinder (a Grace Ice &
Water Shield inner cylinder) with a few light coats of polyurethane finish
and 3/32" acrylic end disks glued in with epoxy.
www.tfcbooks.com/teslafaq/000_0298-1_small.jpg This is a Tesla receiving
transformer with widely-adjustable variable elevated terminal. The terminal
is not very robust but it does give a very wide range of tuning and this is
particularly useful when first configuring a Tesla coil transmitter-Tesla
receiving coil pair.
For the electrical load, it is best to use a very small incandescent lamp
connected to the receiving transformer's secondary winding. I like to use a
single low voltage clear Christmas tree light because they are cheap and
plentiful, and perform well. A low intensity LED will also perform quite
well and will light at more than twice the distance because of the lower
current drain that is placed upon the receiver.
Visit the Tesla's Wireless Work website at www.teslaradio.com/ for the
specifications of this particular Tesla transmitting-receiving outfit.
For wireless transmission it is desirable to increase the break rate up as
close as possible to the vibration rate of the resonator. It is also
important to charge the primary capacitor with direct current. The
objective is simply to achieve the greatest potential on the elevated
terminal with the greatest possible break rate with no sparks issuing.
Once you have the transmitter built and in place with a robust ground
connection and an elevated terminal, adjust the primary capacitor and the
primary tap so that the primary vibration is the same as the secondary
vibration. The objective is to develop the maximum e-field in the vicinity
of the transmitter. Use a cheap analog voltmeter set on a lower AC volts
scale with the COM terminal lead to 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. Also, the transmitter does not have
to be powered up to the point where the thing is almost sizzling and sparks
are just about to break out. When everything is properly tuned up the
transmission and reception takes place even at very low power levels.
The basic Tesla coil design is the essentially same whether it be used for
the creation of artificial lightning or wireless transmission, with the
general exception of the topload being elevated above the helical
resonator's top turn. For a constant diameter of resonator, the length of
the vertical cylindrical conductor between its top turn up to the elevated
terminal can be shortened and at the same time the resonator itself
lengthened until a point is reached at which the topload is once again
directly adjacent to the top turn.
The individual experimenter doesn't need a large high-power Tesla-coil
transmitter to learn a lot about the wireless transmission of electrical
energy Tesla style, and to produce meaningful results. Anyone with a small
solid-state Tesla coil can do this. Actually smaller may be better because
this allows the close in near-field demonstrations to be performed inside of
a Faraday cage. Here are some guidelines.
For the transmitter:
1) Use a 7 : 1 to 9 : 1 aspect-ratio coil form wound with about 1,100 to
1,800 turns of wire.
2) Position the transformer about 25 feet or more from a good Earth
connection, and connect the two using a piece of insulated #12 or larger
stranded wire laying on the ground.
3) Use a well filtered DC power supply or battery bank in conjunction with a
high precision pulse generator to drive a unidirectional switching circuit,
i.e., don't use the four-device bridge circuit. Connect the pulse generator
to the SSTC driver circuit with about 25 feet of RG-58 coaxial cable. Use
optical isolation; the coax could be replaced with fiber optic cable. Start
out with the pulse generator set to a 49% duty cycle and tweak the timing.
5) Elevate the topload so it's about 1.5 times the bottom-to-top secondary
height above the secondary's top turn.
4) For high power oscillators increase the size of the topload so that
streamers do not escape from it when the oscillator is operating at maximum
power.
6) Tune the oscillator to its fundamental resonant frequency by observing
the reaction of an analog voltmeter set to the lowest scale, with one lead
connected to ground and the other connected to a nearby elevated terminal. A
neon lamp is good for course adjustment. A frequency counter also helps, as
will an oscilloscope.
7) If your solid state Tesla coil's coefficient of coupling is tight, try
loosening it.
For a passive receiver or wavemeter:
1) Construct a coil stand out of 2 1/2" white PVC pipe and 6 pieces of 22" x
1' x 1/2", fastened with 1/4" x 20 brass bolts to form a tripod. (See
http://www.teslaradio.com/images/Telluride01.jpg for an example.) This type
of stand is great for the TC transmitter as well (see
http://www.teslaradio.com/images/Telluride04.jpg.
2) Construct an adjustable topload using piece of heavy-duty aluminum foil,
4' long by 18" wide, wrapped around a 20" wooden dowel, mounted on a small
board with end brackets. Before starting the wrap, fold one end of the foil
around a piece of bare copper wire, with one end flush and the other
extending out 2", and solder it to a copper slip-ring installed on one end
of the dowel. (The topload will be connected to the coil with a piece of
wire run to a strip of springy metal pressing on this slip ring.) Now roll
a few inches of the foil's free end on to a 20" wooden batten and then
sandwich it with a second batten, and attach a pull cord of light nylon
line. Mount the entire assembly on a vertical section of 1 1/2" black PVC
pipe. Use a 1 1/2" to 2 1/2" slip bushing and a 2 1/2 " to 2 1/2" coupling
to mate to the 2 1/2" pipe. Tuning is accomplished by pulling the foil out
from the roller like a window shade. This arrangement works well,
especially if there is little or no wind. One difficulty is the need to tip
the whole apparatus to its' side in order to roll back the foil when its
adjusted past peak resonance. An alternative arrangement is two telescoping
PVC pipes with a cord and pulley arrangement (see
http://www.teslaradio.com/images/Telluride02.jpg.) This more robust
elevated cap assembly allows a topload of fixed dimensions to be raised and
lowered at will. The coil-to-topload connection is with a festoon possibly
made with a conductor stripped from a piece of hard elevated telephone drop
wire.
3) Obtain a 1.5 : 1 to 3 : 1 aspect-ratio coil form on which to wind the
receiver's resonator coil. Fill it with a piece of wire the size and length
of which will result in a coil that, with the adjustable topload attached
and set at or near its smallest capacity, is resonant at a slightly higher
frequency than the transmitter frequency. This is the receiving
transformer's primary coil. A higher aspect-ratio primary can also be used.
A miniature receiving coil can be created using an empty aluminum foil tube
wound with AWG #40. A removable secondary can be wound on a short section
of paper towel roll. Tuning can be accomplished with a moveable ferrite
rod, such as used for AM radio loop stick antennas.
4) Ground the resonator using a piece of insulated #12 cord about 25' to 50'
in length as is done with the transmitter. Good results can be achieved
using a standard ground rod 8' or longer driven into soaking-wet earth. Fire
hydrants and steel well casings also work well.
5) Wind a secondary coil around the primary, close to its base. Instead of a
solid conductor, it may be better to use a piece of insulated wire from a
split-in-two zipcord, or a long piece of test-lead wire. A small
low-voltage incandescent Christmas tree lamp is connected to the secondary
as a load. A small permanent magnet DC motor can be run through a 4-diode
bridge rectifier. Work with this arrangement for a while to hone your tuning
skills.
6) For long distance reception the secondary used in step #5 is not used. A
conventional long-wave communications receiver is capacitively coupled to
the primary circuit instead. This is done by running a lead from the
receiver's antenna terminal across and up to a point on or near the PVC
pipe, about 2 ft. above the top turn of the resonator. A second lead is run
from the receiver's ground terminal to a common grounding point fastened to
one of the tripod legs. Tune both the helical resonator and the receiver to
the transmission frequency; try adjusting the antenna-to-resonator coupling
for effect. Nearby objects such as hillsides, trees and buildings have a
noticeable effect on tuning, so get as much out in the open as possible.
You'll find that you have to step back from the coil to avoid detuning of
the resonator, and to get maximum resonant rise. Watch the "S" meter as you
move forward and back, as this helps with fine tuning. Have an assistant
sweep the pulse repetition rate through the resonator's center frequency and
observe the effects on the signal strength and background noise level. An
oscilloscope can be used in place of the receiver. A sensitive e-field
probe will also produce good results.
A few additional suggestions:
1) Join the Wireless Energy Transmission Yahoo Group located at
http://tech.groups.yahoo.com/group/wireless_energy_transmission/ ;
2) Pursue an amateur radio operator's license, General Class or higher;
3) Familiarize yourself with the following:
1a) FCC 47 CFR Part-5 Rules: Experimental Radio Service (other than
broadcast) http://www.access.gpo.gov/nara/cfr/waisidx_02/47cfr5_02.html
1b) OET Experimental Licensing System (Under Part-5 Rules)
https://gullfoss2.fcc.gov/prod/oet/cf/els/index.cfm
1c) Application For New or Modified Experimental Radio Station Authorization
(Form 442) https://gullfoss2.fcc.gov/prod/oet/cf/els/forms/442Entry.cfm
2a) FCC 47 CFR Part-18 Rules: Industrial, Scientific, and Medical Equipment
http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/cfr/1998/47cfr18.pdf
2b) Methods of Measurements of Radio Noise Emissions from Industrial,
Scientific and Medical Equipment
http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/measurement/mp5/mp5-1986.pdf
3a) FCC 47 CFR Part-15 Rules: Unlicensed RF Devices
http://www.fcc.gov/oet/info/rules/part15/part15-2-16-06.pdf
REFERENCES
www.teslaradio.com/pages/bibliography.htm
Regards,
Gary
Gary Peterson
Twenty First Century Books
P.O. Box 2001
Breckenridge, CO 80424-2001
Phone: 970-453-9293 Fax: 970-453-6692
www.teslaradio.com
www.teslabooks.com
www.teslascience.org
www.ntmsc.org
----- Original Message -----
Subject: Re: indication of good tuning (fwd)
> This is Matthew Boddicker again.
>
> I was thinking, Maybe a large spark shows such a large output that sparks
> are just expected. A lack of sparks, on the same line a thought, would
> show a weak output.
>
> I guess it would help if I mention my ultimate goal. I am going to do a
> large scale version of a recently completed research project. A paper of
> the project is attached to this e-mail.
>
> I am trying to see if power transmission is effecient through the earth or
> the air. I believe it is mentioned in the paper that I don't know if my
> system used the air, the earth, or both to power the flourescent
> lightbulb. The next project should find that out by measuring the
> effeciency using the earth, and then the air.
>
> Feel free to make any comments on the paper. It probably needs to be
> updated again to stay current with my facts. The only request I make is if
> all information can be backed by a website, article, or book that I can
> look at.
>
> Thank you all.
> Matthew Boddicker
>> From: "Tesla list" <tesla@xxxxxxxxxx>
>> To: tesla@xxxxxxxxxx
>> Subject: Re: indication of good tuning (fwd)
>> Date: Thu, 2 Aug 2007 11:18:14 -0600 (MDT)
>>
>> ---------- Forwarded message ----------
>> Date: Thu, 02 Aug 2007 17:07:09 +0000
>> From: David Rieben <drieben@xxxxxxxxxxx>
>> To: Tesla list <tesla@xxxxxxxxxx>
>> Cc: drieben@xxxxxxxxxxx
>> Subject: Re: indication of good tuning (fwd)
>>
>> Hi Matthew,
>>
>> Well, that would all depend on what you wanted. Truely a spark spitting
>> coil is not an efficient radio wave broadcaster and conversely, a good
>> broadcaster of EMF and such is not a very good spark maker. Most Tesla
>> coil hobbiest are after the biggest sparks possible from their particular
>> setup. Besides, broadcasting a lot of EMF, radio waves and such may very
>> well put you on the crap list of the FCC - not good.
>>
>>
>> David Rieben
>>> -------------- Original message --------------
>>> Date: Thu, 02 Aug 2007 11:05:24 -0500
>>> From: Matthew Boddicker
>>> To: tesla@xxxxxxxxxx
>>> Subject: indication of good tuning
>>>
>>> Hi everyone, this is Matthew Boddicker.
>>>
>>> Around five months ago read that a coil is properly tuned when it has
>>> the maximum spark length coming out of the top load.
>>>
>>> I also heard a logical argument saying, "Having sparks coming out of the
>>> top load is wasted energy, showing that the coil isn't properly tuned
>>> due to its inefficiency." Something to that effect anyway.
>>>
>>> So what is the best indication of a properly tuned coil? Minimal spark
>>> length or maximum spark length?
>>>
>>> Thanks!