Peter, whatever happened with Eric P. Dollard?

[madhatter]

I just asked Eric about this. This is correct. In order to get the correct spacing copper tubing would need to be used. The 62% spacing is a limiting case. (I'm unclear on why) Ideally, we would have it spaced at 62%. Your build should still work so long as the DIAMETER TO HEIGHT RATIOS OF THE COILS ARE CORRECT. Follow the ratios of dimensions in the Colorado Springs Notes. Eric reiterated that we just build it and see what it does.

Dave

a couple posts or pages back I asked about the skin depth because of this. running the calcs shows that the height divided by the square root of the frequency at 1000kHz has a skin depth that is ~80% of the wire dia, whereas the space factor eq is only 2.8% it gets worse from there though for at 3MHz it's 264.44% vs 4.85% however that raises the question of hollow wire in thousands of an inch. at that point you'd either be using custom litz wire coax or substituting for equivalent solid in the larger dia of the space factor equation.

from what I gather from the equations although it works when close to be accurate and see a clear delta between the TM and LM waves it would require custom wire or designing around the available wire and coax and then broadcasting at that frequency and using both TM and LM receivers to measure the propagation velocity.

[madhatter]

In the videos there are only two coils in the setup, the primary and the secondary. I've not seen the extra coil being employed in the 'crystal set' other than the schematic.

I'll have to retry things again. I took the primary and disconnected the secondary from it's ground and set the meter to read the Hz between the ground point of the secondary and the top of the extra coil where normally one lead to the phones would be, or to state better the meter was in place of the phones, per the schematic the diodes and capacitor was in place. I noticed an interesting effect, If I touched the ground side and stood within 1ft of the coils there was no Hz from 1ft to 4ft it would pick up the 60Hz mains that saturate our environment from my body capacitance, the fact that there was a range was intriguing. taking more readings the mV would peak if I stood 2'6" or the center of the range from the coils. Now if that is due to my body area or not I'll need to test further. The Hz would also scale depending on where in that space I stood, thought the frequency would not change as I moved my arm the voltage would swing wildly, it did peak at 3.7volts when my hand was within inches of an overhead power cord.

Honestly I'm far more comfortable with equations and calculations it's turning that into functioning eq that gets frustrating, odd to since my day job is designing and fabricating however it doesn't entail electrical equipment.

I have sourced some useful equipment and can usually figure which end is up, in this case when I see electronics I start to think in terms of my physics background and that leads to problems. It's a hard habit to break.

still need to source a scope, and some RF meters.

Here's one problem, pizeo earbuds or headphones, Philmore has discontinued mfg and the local electronics supply house has no idea where to procure them from. radio shack no longer carries them either. I'll have to source some off the net, bugger to considering shipping is always expensive and I'm located in socal where normally you can find anything by running down the street if you don't trip over it first!

At this point I have no audio means of detection and the digital meter is more than likely loading the set too.

[Web000x]

The last equation is for a solid conductor. If you you use this equation you can not use the 62% spacing because that is based on the ideal wire diameter giving you the proper "effect". BUT coil height to width ratio is a much more important feature so you would have to increase the spacing to fill the entire coil with the thinner wire I THINK, maybe, possibly

I just asked Eric about this. This is correct. In order to get the correct spacing copper tubing would need to be used. The 62% spacing is a limiting case. (I'm unclear on why) Ideally, we would have it spaced at 62%. Your build should still work so long as the DIAMETER TO HEIGHT RATIOS OF THE COILS ARE CORRECT. Follow the ratios of dimensions in the Colorado Springs Notes. Eric reiterated that we just build it and see what it does.

Dave

[garrettm4]

Crystal Set Trouble Shooting and Thoughts on Engendered Solenoid Field Structures

I posted some of this in the Yahoo Group, and thought it might be of help to people here. Also, I did some reading in the references (that I could actually get my hands on) listed in the Radiotron Handbook 4th Ed for the Section "Short-Wave Coils" with specific focus on Coil-Capacity and came across some interesting things.

Crystal Set Trouble Shooting:

For everyone who has built a "crystal set" and are not getting results, watch the video uploaded by Paul Park on YouTube:

Borderland Sciences - The Tesla-Marconi Wireless System [1988]

Specifically, watch the part where Eric is playing around with the prototype coil (built earlier and demonstrated in prior videos), jump to approximately 00:57:25 (to about 01:07:00, 10 minuets total) where he shows how to play around with the terminal-capacity with a whip and by moving your hands around the secondary, he also talks about a few more things that might help with the troubles some people are having.

It would seem a GOOD ground and PROPER terminal-capacity is probably the culprit for most failures to receive any signals.

One thing I would like to point out to everyone building the Crystal Set, or a Tesla Transformer, is that the LENGTH of the wire is a very very important thing. The Coil-Form dimensions, number of turns, wire diameter, wire thickness, wire material, and everything else ARE ARBITRARY. These arbitrary parameters are what decide the Q or quality factor of the one wire transmission line which we are striving to build. These arbitrary factors are VERY IMPORTANT, BUT they can be bodged around a bit with everything still working in the end. So if having issues move your coil connections along the secondary, making it appear smaller and longer and watch what happens. Also FORGET about the extra coil for right now, JUST USE THE SECONDARY WITH A TERMINAL-CAPACITY AND GROUND CONNECTION AND THEN USE THE PRIMARY FOR HOOKING UP TO EQUIPMENT.

If needed go OUTSIDE and play around with connecting to things for a ground connection and see if that helps.

ALSO, NOTE THAT RADIO FREQUENCY VOLTAGES AND CURRENTS CAN NOT BE ACCURATELY MEASURED BY MOST DIGITAL VOLT METERS, my "high-end" Fluke 289 is only good for 100kcps and my "super-duper" Keithley 2701 (basically a 2000) is also no good with 300kcps, so don't expect a dollar-store voltmeter to be any better. If using a voltmeter, ideally you would need a Keithley 2001 or 2002 (or equivalent), which are rated for 1 mega cycle of bandwidth. BUT, you will find that they too aren't really that helpful, because you will need even MORE bandwidth. SO USE AN OSCILLOSCOPE WITH ENOUGH BANDWIDTH FOR ALL MEASUREMENTS (for harmonic waves you need extra bandwidth). For ground current measurements use a Tektronix p6021, p6022 or A6302 current probe or high-bandwidth equivalent. DO NOT USE A RESISTOR INLINE for current measurements, as it will not give an accurate reading. Note that bandwidth given for most equipment is usually the 3rd decibel nee of the response curve. This means that if measuring at the max rated frequency you will measure about 2/3rds the magnitude of what it really is and when over the max specified bandwidth, the displayed reading will be absolutely useless, for all intents and purposes. SO MORE BANDWIDTH IS ALWAYS A GOOD THING, although it is an expensive luxury. You should always have at least 5x the bandwidth of the source signal frequency for the measuring equipment to get accurate results.

For help on understanding how to make accurate HF measurements read High-frequency Measurements By August Hund published 1951, you will have to create a guest account and login before you can read the book. Click here HathiTrust and set up a guest account then read the book. Also August Hund has another book that might be of interest to those working on the AM Radio Crystal Set, it is called Frequency Modulation published 1942, don't let the title fool you it covers AM, PM and FM Radio.

If you don't have any of the listed equipment then use an old AM radio as an amplifier, or just an audio amp and speaker, and determine the operating adjustments by the sound level output of the speaker. Alternatively, pick up some, if you can find them, "old" HF Radio gauges for current and voltage measurements.(finding these older RF gauges are like looking for "hens teeth")

Once you get a good signal, hookup a light bulb and continue to make adjustments, use critical thinking, systematically change the terminal-capacity's value, primary capacity, connecting wire placement and other parameters, SEE WHAT DID OR DIDN'T WORK, THINK ABOUT THE CHANGES YOU HAVE MADE. USE SOME MORE CRITICAL THINKING AND MAKE CORRECTIONS TO MISCONCEPTIONS IN THOUGHT YOU MAY OR MAY NOT HAVE HAD ON HOW THE UNIT IS "SUPPOSED" TO OPERATE.

Remember the coil plans given by Mr. Dollard ARE EXPERIMENTAL, so it follows that some "experimenting" and lots of ADJUSTMENTS are needed to get the unit YOU MADE to work as it should.

Engendered Solenoid Field Structures:


REFERENCES:

JM Miller - Oscillations in Antennas & Inductance Coils [1918]

A Hund - Oscillations in Antennas & Inductance Coils [1919]

JH Morecroft - Resistance & Capacitance of Coils at Radio Frequencies [1922]

RG Medhurst - H. F. Resistance and Self-Capacitance of Single-Layer Solenoids" [1947] (two part article and quality of digital copy is terrible)

DW Knight - Self-Resonance & Self-Capacitance of Solenoid Coils [2010] (this is an interesting read and pertains to the Medhurst article above)

Garrett M

[dR-Green]

For those who have managed a radio signal from the 3 coil setup, how? I've built and re-wound these coils till I'm dizzy and get zip nada nothing, i've matched surface area, tried density, re-calc'd and re-crunched the numbers. I've also tried the 3 different schematics looking for anything and get nothing.

a simple AM crystal radio works fine, but the primary, 2nd and extra coil arrangement net nothing.

I haven't tried a 3 coil setup, but instead of winding and unwinding coils I suggest you just "get in there" if you haven't already. Use your hands at various points and distances around/along the coil to vary its frequency. I also recommend using an audio amplifier for this stage so you can clearly hear whatever is coming out of it, it will make the job of finding the signal a lot easier.

How will using a signal generator to transmit be picked up if they cannot receive it?

Do you have an oscilloscope? The way I connected it up was the normal way people use to find the resonant frequency of their secondary - connect the signal generator to the bottom end of the secondary. Then you can see the signal on the primary.

The same thing applies to the radio signal. What do you see on the primary? Remove the C0 plate and disconnect any wires that go from the diode to the plate, maybe even remove the "audio" side of the circuit completely, then look at the primary again. Also try the same without the extra coil.

Also similar to the common method of finding the resonant frequency of a "Tesla coil" secondary when driving it with a signal generator, you should be able to put the scope probe near the top terminal and see the "magnified" radio signal. There should be something going on everywhere. The primary should have the same signal as as you see from the top terminal. If you don't then it's not engaging the primary.

I have also found it advantageous to use a separate earth connection for the secondary.

FYI I'm using a flat spiral with approx 51.65m of 24 SWG (0.56mm) wire with 2mm and 4mm spacing (double layer turns) for 882kHz, the calculations for which being about 54m and 16 SWG, so I don't think this is too much of an issue and won't be the cause of a complete lack of signal, unless there are very big differences due to the geometry.

[edit] This is the order I would suggest for reasons including simplicity and avoiding making any permanent changes like cutting the wire. That can be done later if necessary after it has been fully tested. The point of this is to find out what's going on.

Set it all up according to the crystal receiver schematic. Put scope probe across primary. Disconnect secondary from earth and connect it to the signal generator set at the radio station frequency. I assume at this point you are seeing the signal on the primary. If not, adjust the primary capacitance and also move your hands around the secondary/extra coil and see what happens. Perhaps remove the extra coil and do the same (with terminal capacitance connected to top of secondary) and see what happens there. If you are not seeing anything at all then I would suspect it's to do with the primary coupling.

Either way, optionally put normal receiver antenna near the top terminal with another probe across its primary, assuming once again that the top terminal will be radiating the signal and if it's not then there's something fundamentally wrong, and get them into phase unison. You should be seeing some sort of signal around the terminal even if the coil isn't perfectly tuned.

Assuming you are seeing the signal on the primary, see what effect the antenna of the normal receiver has on the Tesla receiver around the terminal, and also moving your hands around the coil. Basically, get an idea of what you see on the scope when you are doing these things. Once you are satisfied with all that, remove the signal generator and connect the secondary to earth (also move the other antenna away to where you'd normally use it). Make note of the normal receiver radio signal on the scope because this is the waveform you want to see on the Tesla receiver, so it will make identifying it that much easier. Connect an audio amplifier and speakers so you can hear what's going on and also see it on the scope, and be prepared to mute and unmute the normal receiver etc. Then repeat the frequency adjustments via primary capacitance and hands around the coil. You can hold the probe around the top terminal at this point to see what's coming through it, again moving your hands and adjusting capacitance. Also try the same without the audio side connected and the C0 plate removed because it will be slightly different. There should at least be "something" there.

Keep adjusting things with primary capacitance and your hands until you can see the same waveform around the top terminal as you are seeing from the normal receiver. This then means you are at least receiving the signal. Then you will need to adjust the primary to see the same signal there, because once you can see the signal through the secondary via various groundings or however you manage it it doesn't necessarily mean the the primary is in tune with the secondary, so continue to adjust it. Once you get an idea of how things are affected then it will make more sense. Also try the tests without a metal plate ground plane if you are using one. If you find something happens with your hands in a certain location then try to use an earthed plate there, or adjusting the size and distance of it etc. If you aren't seeing anything around the top terminal to begin with then you are not receiving any signal so all the rest won't solve it. That would probably be down to the earthing. I can sometimes pick up some French station and at least two others in this country in addition to the main one I'm receiving, so if there's nothing at all happening on yours then that's probably the cause.

Oh yeah, and dodgy connections can really make things all the more confusing even if it looks like everything's working properly according to the scope and you're still hearing a hum so you know the audio output is still connected, but the sound of the radio has completely vanished.

[madhatter]

I believe the first equation is the "ideal" conductor. It would be hollow and have the perfect diameter to spacing ratio to fill the coil height with 20 turns. It could be solid but then you would have to calculate the proper skin depth and calculate volume of active metal and match that with the volume in the extra coil. It is much easier to use hollow conductor with a really thin wall(coax). Then you just need to match the mass.

The last equation is for a solid conductor. If you you use this equation you can not use the 62% spacing because that is based on the ideal wire diameter giving you the proper "effect". BUT coil height to width ratio is a much more important feature so you would have to increase the spacing to fill the entire coil with the thinner wire I THINK, maybe, possibly

This would give you 100% skin depth throughout the conductor.
That way you could still use mass, but you would still be sacrificing on the proper conductor diameter to spacing effect. Not super important since 14ga was recommend as a good compromise.

Hope this helps, feel free to rip me a new one if I'm wrong.

jake

The only problem is that mass is not parameter that needs to be matched and wold very difficult to do so. The coax use for the secondary raised even more questions I asked previously and was told it wasn't critical. I have the highly complex equation for coax braid and after running the calc there is not a single coax in existence that fits the calcs for 1000kHz or the 1070kHz I was designing for.

That's where I decided on moving to solid, the equations as seen are not equal unless you move the decimal place and factor the sqrt of Hz and not kHz, then the two are very very close to equal.

If using a hollow conductor then copper tube would be best, I'm not aware of any supplier for tubing in lengths over 100', so back to increasing the Fq then dealing with the size reduction.

[jake]

examining the posts on the coil calcs I've run into some questions, there is one sheet with a 30 turn reference any ideas on why? the other has to do with the secondary wire dia.

From “Calculating Process For a tesla coil”
(4) side by side wire spacing, given 62% of wire diameter, given for 20 turns, a wire diameter,
d=h/32.8
The above was considered in an earlier post as a numerical error so that 32.8 should be 31.78.
Another posting:
Number of turns = 30
Space factor: a = 30+18 = 48
This being derived from a=[n+(n-1)0.62]
Wire dia,
d=h⁄48

Another posting:
20 turn secondary coil
Maximum solid conductor diameter,
d_s=5.1 x 〖10〗^1 ÷√f
Or
d_s=h⁄(√f)

If we run the calcs for each based on 1000kHz
0.4782 cm, 20 turn
0.2111 cm, 30 turn
0.0151 cm, 20 turn
Aside from the odd 30 turn sheet that was posted there is a difference in the two 20 turn secondary coil equations that have been posted.
The equation in example 1 & 2, checks out by taking the wire dia given and adding in the 62% of the wire dia to total and it will equate to the height. The third eq ends up being only 31.466% of the coil height. If instead of using Hz but kHz as the frequency it’s a bit closer, but kHz is not 1 per second as noted in the post.

-note- the equations above are in LaTex but don't seem to translate here in the post.

I believe the first equation is the "ideal" conductor. It would be hollow and have the perfect diameter to spacing ratio to fill the coil height with 20 turns. It could be solid but then you would have to calculate the proper skin depth and calculate volume of active metal and match that with the volume in the extra coil. It is much easier to use hollow conductor with a really thin wall(coax). Then you just need to match the mass.

The last equation is for a solid conductor. If you you use this equation you can not use the 62% spacing because that is based on the ideal wire diameter giving you the proper "effect". BUT coil height to width ratio is a much more important feature so you would have to increase the spacing to fill the entire coil with the thinner wire I THINK, maybe, possibly

This would give you 100% skin depth throughout the conductor.
That way you could still use mass, but you would still be sacrificing on the proper conductor diameter to spacing effect. Not super important since 14ga was recommend as a good compromise.

Hope this helps, feel free to rip me a new one if I'm wrong.

jake

[Kokomoj0]

could this be the issue? from post #1109 byT-Rex:


How will using a signal generator to transmit be picked up if they cannot receive it?

lets see how would I test that.

Ok I would connect it to the ground with a 1 ohm resistor between the ground lead and the set (coils etc), then on the coil side of the 1ohm resistor I would start with a 1mg ohm series feed resistor (from the generator signal lead) with the ground lead of the generator connected to ground side of the resistor and sweep the band to see where my tuning was at. It would be important to keep the series r as high as possible to prevent loading the coils.

oh and by start with a 1mg ohm series feed resistor I mean you may have to lower it depending on voltage of your generator and the sensitivity of your receiver setup. then sweep the generator to find out where you are tuned, start snipping and trimming or add/subtract capacitors, change wire spacing etc etc etc whatever it takes to bring it into the desired bandwidth.

[madhatter]

What sort of grounding arrangment are you using?
Remember the radio signal we are attempting to receive is the underground transmission. So unless there is a solid connection to the Earth, it will be difficult to receive anything.

At least you have constructed something, my build is still under construction (Some how my coaxial cable order has not yet arrived, seems it's lost in the mail)? The formers are built, await winding.
Grounding will be many copper rods into the ground. (I found some masonary drill-bits, 25mm diameter, and 1meter long. With an extension, I should get at least 2 meters deep (hope for more). Hammer then the matching Copper rods into drill holes. Connect together with heavy strap and solder.
Smokey has some good info on coils and diodes on the yahoo group.

keep try'n.

you're correct about the grounding issue, using the water main is not effective and only imparts 60Hz. I don't want to have to build a radial ground rod setup as I don't have the room.

Also in going over the eq. in order to build exactly to the wire dia and spacing I'd need 5awg wire, way to expensive!

I figure at this point I'll build twin setups and use the signal generator, probably in 3.5mHz range as the coils are smaller and easier to manage also the gauge of wire is easier to manage as I've got most sizes under 8awg.

I'm unclear on the coax useage as well, there isn't a coax small enough for the extra coil and on the secondary it makes it very very difficult to match for the extra in solid.

[Sputins]

Golden Video

The following is a presentation given by Eric at the San Francisco Tesla Society on December 9, 2007. I'm working on getting the corresponding Powerpoint presentation to go along with it.

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 1 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 2 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 3 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 4 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 5 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 6 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 7 - YouTube

Eric Dollard - S.F.T.S. - Dec. 9, 2007 - Part 8 - YouTube

When asked if he wanted to sell copies of this presentation, Eric said "No, just put it out there". Sorry for the redundancy, but please donate to this man. He makes WAY LESS money that he should for all of his efforts to help us.

Dave

WONDERFUL STUFF DAVE!!!!!!!!

It' s very honourable for Eric to say "just put it out there", even though he might have made a few $'s from it.

I will study the lecture and report back.

Can't believe it, great stuff!

Three cheers for Mr Eric Dollard!

[Sputins]

Grounding system?

a simple AM crystal radio works fine, but the primary, 2nd and extra coil arrangement net nothing.

What sort of grounding arrangment are you using?
Remember the radio signal we are attempting to receive is the underground transmission. So unless there is a solid connection to the Earth, it will be difficult to receive anything.

At least you have constructed something, my build is still under construction (Some how my coaxial cable order has not yet arrived, seems it's lost in the mail)? The formers are built, await winding.
Grounding will be many copper rods into the ground. (I found some masonary drill-bits, 25mm diameter, and 1meter long. With an extension, I should get at least 2 meters deep (hope for more). Hammer then the matching Copper rods into drill holes. Connect together with heavy strap and solder.
Smokey has some good info on coils and diodes on the yahoo group.

keep try'n.

[madhatter]

could this be the issue? from post #1109 byT-Rex:

"8) Underground vs over ground. Two identical Tesla units will not compare. They cannot receive E.M. waves. For over ground use a conventional crystal set with a dipole, not a ground Marconi antenna. A loop type receiver is even better, a big loop over ground and a big star radial underground. Thus a dipolar connection over ground, a monopolar connection underground. The Landers Mojave Research Installation used a beverage over ground and a wideband Alexanderson underground."

How will using a signal generator to transmit be picked up if they cannot receive it?

[Kokomoj0]

No idea, please explain the 'tiny tank'.

one of the other things is the eq for the coils have some inconsistencies as posted. I'll put them in a new post.

just to load the generator, it will transmit a very short range, enough to check your tuning without physical connection.

if you have a strong enough generator could also use a 50ohm resistor

you really need to find out where the coils are resonating and their tunable bandwith.

[madhatter]

examining the posts on the coil calcs I've run into some questions, there is one sheet with a 30 turn reference any ideas on why? the other has to do with the secondary wire dia.

From “Calculating Process For a tesla coil”
(4) side by side wire spacing, given 62% of wire diameter, given for 20 turns, a wire diameter,
d=h/32.8
The above was considered in an earlier post as a numerical error so that 32.8 should be 31.78.
Another posting:
Number of turns = 30
Space factor: a = 30+18 = 48
This being derived from a=[n+(n-1)0.62]
Wire dia,
d=h⁄48

Another posting:
20 turn secondary coil
Maximum solid conductor diameter,
d_s=5.1 x 〖10〗^1 ÷√f
Or
d_s=h⁄(√f)

If we run the calcs for each based on 1000kHz
0.4782 cm, 20 turn
0.2111 cm, 30 turn
0.0151 cm, 20 turn
Aside from the odd 30 turn sheet that was posted there is a difference in the two 20 turn secondary coil equations that have been posted.
The equation in example 1 & 2, checks out by taking the wire dia given and adding in the 62% of the wire dia to total and it will equate to the height. The third eq ends up being only 31.466% of the coil height. If instead of using Hz but kHz as the frequency it’s a bit closer, but kHz is not 1 per second as noted in the post.

-note- the equations above are in LaTex but don't seem to translate here in the post.

[madhatter]

are you able to get it to resonate at and around the freq of the station?

if you make a tiny tank and drive it on the same freq near the receiver it should go nuts, if not you may not be tuned properly?

No idea, please explain the 'tiny tank'.

one of the other things is the eq for the coils have some inconsistencies as posted. I'll put them in a new post.