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  • #46
    Originally posted by xee2 View Post
    Congratulations. Thanks for the report and photo. Is your only antenna the short wire on top of the primary coil (or are you connecting to an external antenna wire in addition to the fireplace ground)? Please post a link to the page where you got the EPD info.

    First four equations are the most important as far as I can tell. (wire length, turn length, coil diameter, coil hight) Primary width is 18% of coil diameter but I cant find the post. It's somewhere on the "Peter what happened to Eric" thread, search the T-Rex posts. If you can figure out how to incorporate the other items into your build without loosing the first 4 the the better according to EPD. Not having the correct size tube, I used 14 gauge as recommended by Eric. Coax is also recommended by Eric but I felt this was a compromise to another extream, so I went with the 14 gauge solid.

    There are a few excell calculators on the yahoo group. I wrote the TRTcalc3.xls. These will do the math for you. If you are not a member PM me and I will send it to you. We cant post excel files here. Now that I think about it I should update that spreadsheet again.

    As you know from you exciter experience there are variables in designing a coil. This way, adds a few more variables in the mix. This coil is based on a few ideas EPD described in his writings and old school HAM techniques, brought back to life by EPD. Spaced windings, active copper volume match
    and Erics formule were a few of my considerations.

    The extra coil is still a bit of a mystery. I am not using one. I made one but I have not figured out what it is supposed to do, and how it does it. Erics dimensions were tenetive(as he described) at best and not all the equations make sense to me at least. I am almost ready to revisit that.

    ALSO I got an LED AV plug to glow just as well as the FWBR. One wire to the top of the secondary and another lead off the negative of the LED laying on the tile.

    The fireplace is metal and sticks out of the roof so its like an antenna. but its grounded so I dont know what to call it.

    OK fireplace not needed!!!

    I connected to the mains ground and adjusted the CAN, now the LED is on, bottom of the secondary is mains ground and soda can antenna.
    Attached Files
    Last edited by jake; 04-21-2012, 03:50 AM. Reason: 2 banana


    • #47
      I don't think this is off topic but this link is to a instruct-able on how to make a Tesla lightning detector. It looks really interesting this guy has videos of his device detecting light, and sound waves as well as EM waves. I've been wanting to build one for a long time but never got around to it ;p

      Make the Tesla Spiral Antennas


      • #48
        @ jake

        Thanks for the info. I find lighting an LED with just a few feet of wire for an antenna to be impressive. What kink of results did EPD get with his?


        • #49
          This is the theory for the crystal set initative AND an appropriate experiment for validation. To my knowledge it has not been accomplished. It is based on the following post.

          Originally posted by T-rex View Post

          Crystal Sets Gone Wild

          For the diagram shown the coil dimensions are missing, number of turns, etc. A good ground is essential for these kinds of devices. 16 Ground rods in a 10 to 20 foot radius circle, connected to a single ground rod at the center(17th rod), this connection being 10 gauge wire. Dry sand or rock will not ground, so this requires 80, each 14 gauge wires in a 30 foot diameter circle in a star radial configuration, to a center terminal. Without these groundings a Tesla Transformer cannot properly operate, but some "HI-Z" sets may.

          The objective here is to scale the "Crystal Set", a step at a time, into a Tesla Transformer for the reception of medium wave band, 300 - 3000 kilocycle A.M. broadcasts. No license is required for this and the broadcast station provides the power.

          And this objective cooperates with the primary objective. That is; Who will be the first ham to disprove Einstein's theory? An International contest, but who will sponsor it, Iran maybe?

          We have the good fortune in the "Crystal Set Initiative" that, in theory at least, a quarter wave A.M. broadcast tower, and its 120 quarter wave ground radials, must emit a pair of waves as shown by Tesla in his basic diagrams.

          Hence it can be seen that a pair of waves are engendered by this transmission system. (Tower and Star Radials). One wave, Hertzian, is the over ground wave, the other wave, Telluric, is the under ground wave. These two waves arrive at the point of reception in their own distinct time frames, giving rise to a difference in phase. Hence, multiple rings of interference patterns are produced. Since the Hertzian portion, over ground, time frame is based upon the velocity of light, then the Telluric portion, under ground, time frame gives the Telluric velocity. Two crystal sets, one over ground, one under ground, and a basic oscilloscope , that simple. I have done this at Landers.

          Concluding, a Tesla Magnification Transformer, properly proportioned can, in theory, actually draw power from a local 50 kW station. Several hundred watts of power reception is likely. This would prove Tesla once and for all. No antenna, just a good ground, and a nice and bright 100 watt light bulb.

          This would overturn physics more than any billion dollar C.E.R.N. project. A ham radio operator overturns Einstein for 100 bucks. What a concept.
          Tesla, "The True Wireless"
          Tesla, "System of Concatenated Tuned Circuits"
          Dollard, "System for the Transmission and Reception of Telluric Electric Waves"
          A.R.R.L. "Radio Amatuers Handbook". Chapter "H.F. Transmitters, & Tank Circuits"
          73 DE N6 KPH
          If you consider these tranmissions helpful, please donate to Eric Dollard via PayPal at

          Some more build info form the "Peter where's Eric" thread that was locked.

          I wonder if Aaron could sticky it to the begining of the EPD thread.

          Originally posted by T-rex View Post
          Tesla Type Crystal Radio

          The design of the Tesla Transformer starts with the secondary resonant coil. In its resonant mode it is a quadrapolar resonator. Two constants exist in the construction of this solenoidal resonator, one is that the height to length ratio must be 20%, the other is that the side by side spacing of the cylindrical conductor turns is 62% the diameter of the cylindrical conductor. The optimum number of turns is 20 on the secondary, with 2 on the primary. This gives the physical size of the coil for a given frequency. Increasing the number of turns reduces the size of the secondary coil in proportion to the increase in turns. Accordingly the conductor diameter also decreases as the copper is spread out over more windings. The ratio of secondary turns to primary turns must equal a constraint of 10 to 1. For a given number of turns the operating frequency becomes the sole independent variable in coil design.

          The primary coil is the same diameter as the secondary coil. The ratio of conductor width to coil diameter is 18%. The sheet conductor is closely spiralled into two turns, for a secondary of twenty turns. For a conductor thickness as given by the maximum thickness vs frequency the volume of the primary metal must equal the volume of the secondary metal, based upon equal weights for primary and secondary metals. Brass can be 1.7 times thicker than copper, and bronze can be 2.8 times thicker than copper, for a given maximum thickness and frequency.

          The primary condenser should be made of the same amount of metal as the primary coil. Their weights should be about the same. The connecting leads must be short and the same width as the primary conductor. Large, multiplate air condensers are good, so are metal sheets and glass.

          The secondary capacitance is best a copper tubing ring around the outside of the H end of the coil. This ring must be open in one spot along its loop so as not to be a shorted turn. The end of the secondary wire connects to this capacity ring. Beer cans make the best elevated capacitors.

          The finished transformer must operate on a directly connected ground plane. A large plywood table with aluminum foil glued on to it, this covered with a plastic or glass sheet is the minimum required ground plane. Obviously the aluminum plane must be solidly earthed with special attention to minimizing ground lead inductance. In order to light a lamp a more broadcast station style of ground plane is required, but for testing purposes the metallized plywood "ten by" sheet is just fine. Good luck and good crystal set DX ing.
          There is no step by step guide to tuning this. Following basic DX, crystal set rules do not necessary apply IMHO.

          All the theory is in here: []

          I do not want to talk about theory of operation here. Just observations and diffferences between this design and a normal crystal set design. For an unbiased Theory pull out the T-rex posts from the above thread and read. Not that there is not other great information in that thread but it can make you mind wander. Read the other posts after you determine if you understand Eric or not. I found page 26 a great place to start. Lots of good T-rex posts before that but they are a bit advanced and its hard to apply to those lessons before you understand the basics and that is what this is about.

          Learning the basics.


          • #50
            Originally posted by xee2 View Post
            @ jake

            Thanks for the info. I find lighting an LED with just a few feet of wire for an antenna to be impressive. What kink of results did EPD get with his?
            What powers the wireless AV plug?


            • #51
              RF Probe

              For those who may not have RF test gear, I found a simple RF circuit you can make to read RF voltages on a DMM.

              N5ESE's Classic RF Probe

              I made one this afternoon took about 30mins, used an aluminum cigar tube for the RF shielded body.


              • #52
                Originally posted by jake View Post
                What powers the wireless AV plug?
                The AV plug appears to not have a return, but it actually does. The return path is through capacitive coupling. There is always some amount of capacitive coupling between any two conductors. Touching one side of the LED will increase the capacitance since that allows the high frequency current to flow over the surface of your body and increases the area of the capacitive plate. Normally this requires higher voltage than you have in order to work wirelessly so I am surprised that you can get it to work without a return wire with the voltage you have. The circuit is just a diode rectifier feeding an LED. The diodes prevent the reverse voltage across the LED from getting high enough to burn it out (LEDs can only have about 10 volts of reverse voltage before they will be destroyed).

                see >>> one wire circuit - YouTube


                • #53

                  Originally posted by madhatter View Post
                  For those who may not have RF test gear, I found a simple RF circuit you can make to read RF voltages on a DMM.

                  N5ESE's Classic RF Probe

                  I made one this afternoon took about 30mins, used an aluminum cigar tube for the RF shielded body.
                  That is perfect! But wait lets make it better.

                  I don't care about accuracy. I want maximum sensitivity and stability so I can tell where the peak is. Becides ditching the the resistor should I consider another sized cap? 0.01uF seems a little large for use on a crystal set

                  @ all,

                  When using 0.5v PP on the function generator(lowest setting) across 1 turn of the primary I can use an AV plug to trace the secondary and "see" the high and low points along the entire secondary. Middle 5 turns have close to nothing. All the umph is at the top and bottom of the secondary.

                  Now to get that umph into the extra coil through the cap without loosing anything.


                  • #54
                    @ jake

                    I calculated the field strength voltage 5 miles away from a 1,000 watt transmitter to be 0.03 volts per meter. This is a rough calculation but gives approximate value to be expected. You are getting much more out. I am impressed with your design. I worked several years as an antenna engineer developing very advanced antenna designs, so it takes a bit to impress me.

                    For a 10,000 watt transmitter this increases to about 0.10 volts per meter.

                    After I did the calculations the hard way, I found an online calculator that gives about the same answers:

                    Volt per meter and power density calculator

                    EDIT: A tuned antenna will suck up the RF energy much like an electronic vacuum cleaner, so I would expect your antenna to produce more than the ambient volts. It is actually possible to measure the lack of signal behind a tuned antenna which shows it has absorbed energy from an area much larger than itself.
                    Last edited by xee2; 04-22-2012, 03:03 AM.


                    • #55
                      xee2 you rock

                      The funny thing is: The coil responds best when excited at ~2200kHz. So I may be getting signal from another station but I cant hear it because 1620 is so loud.


                      • #56
                        Originally posted by jake View Post
                        I consider another sized cap? 0.01uF seems a little large for use on a crystal set
                        What cap? There is no reason to go over 100 pf for coupling at 1 MHz. The smaller the coupling cap is the higher the resonator Q will be.


                        • #57
                          Originally posted by jake View Post
                          xee2 you rock

                          The funny thing is: The coil responds best when excited at ~2200kHz. So I may be getting signal from another station but I cant hear it because 1620 is so loud.
                          No. If you are hearing 1620 then that is where the power is coming from. You will hear the station delivering the most power.


                          • #58
                            Hi Jake....nice work.
                            Thought i'd post my setup here for you.
                            I'm getting 25+ volts from my circuit and i can run a wall clock from it very well.
                            I made my own 2 gang vari cap from some bits of aluminium glued to a wooden dowel.
                            I'm using about 30 feet of data cable as antenna but anything works...even just an iron wire.... My antenna is about 12 to 15 feet in the air.
                            My coil is tuned to 774 khz but i also get 1550 khz as well.
                            The 774 station is about 20 kilometers away from me, and i think it is a 50,000 w transmitter....i think?
                            Here is a link showing my setup running a clock.
                            clock radio - YouTube

                            I wind the primary with taps, then i just wind the secondary straight over the primary.
                            I'd like to see someone else try this setup and see how it performs.
                            Attached Files


                            • #59
                              Standing/Stationary "wave"

                              @ all: Does this make sense?? Is this normal antenna theory stuff?

                              I am using bare 14gauge wire. So I can tap it at any point, and I do. There is a standing/stationary wave along the entire coil when excited at ~2200kHz. Max voltage is on the soda can, and again max at the bottom of the secondary by the grounding at ~2200kHz. With an area in the center of tht gives no readings. In this case I am feeding it with a function generator.

                              When attached to my magic "fireplace gouund " I get hightest signal close to the top of the secondary but not on the can and the voltage does not go up at the bottom.

                              This tells me I need more interwinding capacitance or a capacitor across or the split ring the secondary think
                              I think it's time for me to learn YouTube. I'm a video posting virgin. But the standing wave visual is cool.

                              And finally, my detector is an AV plug with germanium diodes. Crystal ear phone is attached across the LED and I can hear the station and the light glows when I tap points. This is the on the unpowered setup. Better yet I can hear the station on the "AV LED-head piece" 1" away from the secondary without touching, and it gets louder the closer you get.

                              Which means I am radiating. Which is bad.

                              So is this normal stuff?


                              • #60
                                @ loadstone


                                Wish I had seen that earlier. Tried earlier on to get a joule thief to work but failed. Then I got good light from the coil directly and dropped that idea. I'm borrowing a function generator so I'm spending my time working with that. I'll eventually get a thief to steal radiowaves.

                                Did you ever work with 1N34 germanium diodes? How do thay compare to the ones in the video?