Announcement

Collapse
No announcement yet.

frequency depth relation diagram

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Originally posted by Skippy View Post
    Would this experiment be better if the buried transmitter were target-sized? It would not be hard to make a 30mm diameter coil with suitable inductance, like 1mH.
    My experiment is only designed to measure transmission efficiency of different frequencies through soil. It doesn't really matter what sized coils you use because your comparing with an air test anyway so although different sized coils will couple better at different frequencies the effect should cancel out.

    To answer the question of what frequency gives the best depth for a given sized target you need to do another experiment testing target excitation at different frequencies. Then you need to find a compromise between maximum target excitation, minimal soil attenuation.

    Midas

    Comment


    • #32
      At the moment I only could detect the field-strengh from
      100 kHz up to 2GHz - but first some kind of portable frequency
      generator has to be built and the coil buried in real soil.

      But those results would be "out of range" anyway.

      The simplest solution is any kind of DIY metaldetector
      where the freq. is adjustable somehow - at least from
      1kHz to 100kHz. To read the frequency the tester should
      have an oscilloscope. The total radiation energy should
      remain the same.

      This would give real test results - because this is 2 way:
      coil -> find and back. Of course different large objects
      should have been buried at a reasonable depth and
      the detector should have at least a VUmeter so the
      detection power is directly readable.

      Too bad that not just a simple loudspeaker can be buried.
      A thin leaf of paper already blocks high audio frequencies.

      Comment


      • #33
        Originally posted by Skippy View Post
        Would this experiment be better if the buried transmitter were target-sized? It would not be hard to make a 30mm diameter coil with suitable inductance, like 1mH.
        Hi
        How strange just built a 30mm coil for a pinpointer im working on, 26gauge 2.7ohms 687uh , even got shielding just connected on the minipulse 3 for a bit of fun right here and now in front of my pc, then this thread comes up.
        So what do you want me to do with it, stick it in the ground or up my.... lol

        Regards
        Dave

        Comment


        • #34
          Originally posted by satdaveuk View Post
          Hi
          How strange just built a 30mm coil for a pinpointer im working on, 26gauge 2.7ohms 687uh , even got shielding just connected on the minipulse 3 for a bit of fun right here and now in front of my pc, then this thread comes up.
          So what do you want me to do with it, stick it in the ground or up my.... lol

          Regards
          Dave
          I think Kang said it best:"..We have reached the limits of what rectal probing can teach us."

          Comment


          • #35
            This is for GPR (out of MD frequency range), but interesting results:

            More here:

            http://www.sciencedirect.com/science...12825204000054
            Attached Files

            Comment


            • #36
              Originally posted by satdaveuk View Post
              Hi
              How strange just built a 30mm coil for a pinpointer im working on, 26gauge 2.7ohms 687uh , even got shielding just connected on the minipulse 3 for a bit of fun right here and now in front of my pc, then this thread comes up.
              So what do you want me to do with it, stick it in the ground or up my.... lol

              Regards
              Dave
              Some times real crazy and unbelievable coincidences are happening.
              In Germany a treasure-hunter found a golden ring with the date
              13 July engraved - guess on what day? On July 13th 2012!

              but "back":
              I hope the Garrett Pro Pointer will not be used by the tax- and
              duty authoritys to find hidden Rolex watches or lost piercings.

              And gays or gals could use this vibrating detector as a sextoy
              or gynecologists for searching metal contraceptive spirals.

              The best excuse ever:
              This thingy under my pillow is not to do filthy stuff,
              that's just my new pinpointer for metal detection!

              Comment


              • #37
                Now after almost 2 weeks this topic exists still noone here knows
                any kind of real useful info of frequency depth relation!

                It must have been some kind of wonder when the big MD
                companies found out that ca. 10kHz work at least somehow.

                Comment


                • #38
                  I see that companies like Minelab have used multiple frequencies for their detectors.
                  Let's say there was an ideal freq for maximum depth in the VLF range. Would it be impractical to use the VLF as a "carrier" and place a much higher freq inside the VLF wave, and use that as the detection freq? (coil limitations?)
                  Also, wouldn't extreme high voltage pulses injected directly into the ground produce "readable" EMF's? (conductive pulse or pulses being detected by induction) Just thinking that maybe a little "kick" with some high voltage in the right spot might make going deep much easier. My thought is, can a high voltage signal be injected into the ground with a probe, then the reflective currents might be read by induction? That would eliminate any coil limitations for TX.
                  I assume that this has been thought of previously but I had to ask just in case.
                  My apologies if I'm too far out of the box.

                  Comment


                  • #39
                    PI and Multi-Frequency - isn't this a misleading describtion?

                    The PI fires a certain amount of strong pulses per second.
                    How should it fire different amounts of pulses (= frequency)
                    at on and the same time?

                    This even isn't a real AM or FM modulation, it's more like
                    half wave or switch light on off situation. Or better comparable
                    with a transformator that always switches on and off.

                    The coil is the trafo-coil (without iron-core) and the secondary
                    coil that has to pick up the EM-field in one.

                    I guess high voltage pulses (already used by PI or better medium
                    voltage ~500v) would be just fine, but alot MDs will blow because
                    those are already high sensitive to High Voltage fields 100m away!

                    If we fire those pulses 10 times per second we'd have 10Hz -
                    extremly low waves at high voltage - perhaps the best combination
                    for real extreme depth penetration.

                    No, this is PI, we need a "powerful steady field" to get the maximum
                    contrast program out of the soil. higher voltage to increase the
                    magnetical strenght of course. Perhaps I have to sacrifice one
                    of my beautiful plasma-balls for low-current high voltage.


                    Would be cool to create some real experiments with the usual
                    home electricity. 230v at 50 or 60Hz should work real good for
                    metal detection! Don't try this at home or in your garden!

                    Comment


                    • #40
                      You forgot electric fences

                      Regarding multi frequency and PI - yes, it is a common practice to test frequency response, as response to multiple frequencies, by Dirac (not unlike PI) or step excitation.

                      Comment


                      • #41
                        Originally posted by Funfinder View Post
                        PI and Multi-Frequency - isn't this a misleading describtion?

                        The PI fires a certain amount of strong pulses per second.
                        How should it fire different amounts of pulses (= frequency)
                        at on and the same time?

                        This even isn't a real AM or FM modulation, it's more like
                        half wave or switch light on off situation. Or better comparable
                        with a transformator that always switches on and off.

                        The coil is the trafo-coil (without iron-core) and the secondary
                        coil that has to pick up the EM-field in one.

                        I guess high voltage pulses (already used by PI or better medium
                        voltage ~500v) would be just fine, but alot MDs will blow because
                        those are already high sensitive to High Voltage fields 100m away!

                        If we fire those pulses 10 times per second we'd have 10Hz -
                        extremly low waves at high voltage - perhaps the best combination
                        for real extreme depth penetration.

                        No, this is PI, we need a "powerful steady field" to get the maximum
                        contrast program out of the soil. higher voltage to increase the
                        magnetical strenght of course. Perhaps I have to sacrifice one
                        of my beautiful plasma-balls for low-current high voltage.


                        Would be cool to create some real experiments with the usual
                        home electricity. 230v at 50 or 60Hz should work real good for
                        metal detection! Don't try this at home or in your garden!
                        I was thinking of something like a CRT flyback transformer. Maybe a triangle of 3 with a Rx coil in the center, tuned to the same 10Hz? The thought was to exchange the Tx inductive pulses or wavelengths for directly coupled, high voltage, low current "injection".
                        This would do away with the Tx being sent from a coil(s) and the complexities of running those two coils so close together. Has anyone confirmed that induction is the best route for Tx?
                        Oscillation in a triangle might be interesting too?
                        I'm thinking that it might be best to think of detecting as being very similar to SONAR. Everything is wavelengths.
                        We're going to figure this stuff out.


                        Originally posted by Funfinder View Post
                        PI and Multi-Frequency - isn't this a misleading describtion?

                        The PI fires a certain amount of strong pulses per second.
                        How should it fire different amounts of pulses (= frequency)
                        at on and the same time?

                        This even isn't a real AM or FM modulation, it's more like
                        half wave or switch light on off situation. Or better comparable
                        with a transformator that always switches on and off.

                        The coil is the trafo-coil (without iron-core) and the secondary
                        coil that has to pick up the EM-field in one.

                        I guess high voltage pulses (already used by PI or better medium
                        voltage ~500v) would be just fine, but alot MDs will blow because
                        those are already high sensitive to High Voltage fields 100m away!

                        If we fire those pulses 10 times per second we'd have 10Hz -
                        extremly low waves at high voltage - perhaps the best combination
                        for real extreme depth penetration.

                        No, this is PI, we need a "powerful steady field" to get the maximum
                        contrast program out of the soil. higher voltage to increase the
                        magnetical strenght of course. Perhaps I have to sacrifice one
                        of my beautiful plasma-balls for low-current high voltage.

                        I was thinking of something like a CRT flyback transformer. Maybe a triangle of 3 with a Rx coil in the center, tuned to the same 10Hz? The thought was to exchange the Tx inductive pulses or wavelengths for directly coupled, high voltage, low current "injection".
                        This would do away with the Tx being sent from a coil(s) and the complexities of running those two coils so close together. Has anyone confirmed that induction is the best route for Tx?
                        Oscillation in a triangle might be interesting too?
                        I'm thinking that it might be best to think of detecting as being very similar to SONAR. Everything is wavelengths.
                        We're going to figure this stuff out.


                        Would be cool to create some real experiments with the usual
                        home electricity. 230v at 50 or 60Hz should work real good for
                        metal detection! Don't try this at home or in your garden!

                        Comment


                        • #42
                          Does anyone consider energy parameter?
                          Attached Files

                          Comment


                          • #43
                            Originally posted by Funfinder View Post
                            PI and Multi-Frequency - isn't this a misleading describtion?

                            The PI fires a certain amount of strong pulses per second.
                            How should it fire different amounts of pulses (= frequency)
                            at on and the same time?

                            This even isn't a real AM or FM modulation, it's more like
                            half wave or switch light on off situation. Or better comparable
                            with a transformator that always switches on and off.

                            The coil is the trafo-coil (without iron-core) and the secondary
                            coil that has to pick up the EM-field in one.

                            I guess high voltage pulses (already used by PI or better medium
                            voltage ~500v) would be just fine, but alot MDs will blow because
                            those are already high sensitive to High Voltage fields 100m away!

                            If we fire those pulses 10 times per second we'd have 10Hz -
                            extremly low waves at high voltage - perhaps the best combination
                            for real extreme depth penetration.

                            No, this is PI, we need a "powerful steady field" to get the maximum
                            contrast program out of the soil. higher voltage to increase the
                            magnetical strenght of course. Perhaps I have to sacrifice one
                            of my beautiful plasma-balls for low-current high voltage.


                            Would be cool to create some real experiments with the usual
                            home electricity. 230v at 50 or 60Hz should work real good for
                            metal detection! Don't try this at home or in your garden!
                            ...then who knows ....the guys digging the hole for your coffin might find some gold

                            Comment

                            Working...
                            X