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TGSL 29.2 KHz

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  • #16
    hello homefire

    can you link the caps calculating programm that you have used some postings above

    thanks bernd

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    • #17
      It was stated that the first link shows up on Protection software as a Trojan but I can't find anything wrong with it. I think his software is flagging on the JavaScript it's made up of. Use at your own risk.

      http://www.whatcircuits.com/lc-reson...cy-calculator/

      http://www.raltron.com/cust/tools/seriescapacitance.asp

      Comment


      • #18
        ok thanks nice tools

        regards bernd

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        • #19
          This Idea is Abandoned.

          Just going to build a Lobo!

          Comment


          • #20
            Originally posted by homefire View Post
            This Idea is Abandoned.

            Just going to build a Lobo!
            Tell us why you gave up. It was an interesting experiment.

            I don't understand comment that increasing TX would decrease phase difference between targets. I would think its the opposite. Can someone explain?

            You would need to examine all the phases of the sync pulses etc. to make sure the discrimination and GB are working as expected or whether you need some mods (probably).

            Probably harder to tune everything at higher freq, but I say keep trying, let us know. We can try to help troubleshoot.

            Regards,

            -SB

            Comment


            • #21
              Originally posted by Skippy View Post
              I'm sure a bit of search engine use will tell you the details, but I recall a skin depth of 0.5mm is common at MD frequencies, so you're probably OK with a single conductor, especially as the Q factor doesn't need to be very high. But I'm sure some Geotech-ers will have more practical experience.
              There is something called "proximity effect" which is similar to skin effect only for a bundle of wires. Our coils may be subject to proximity effect. I think it would mainly raise the effective resistance of the coils.

              -SB

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              • #22
                When I have the funds for a Silverdog kit, I will start on it again.

                It can be done.

                The Fisher GoldBug II runs at 70.01 KHz!

                The Old Tosoro lobo ran at 20KHz.

                Can't tell me what's been done can't be done! LOL
                Attached Files

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                • #23
                  Etrac goes out to 98kHz or something like that

                  I wonder if anyone has done a study of frequcies that get thru soil types best?

                  I am planning a foray into dsp type prototype using PC soundcard so u could do 3.5, 7, 14, 21kHz

                  I have been downloading free apps from Hams who do this stuff a lot.


                  a good one is Rocky.exe and another one with great write up is.. SAq reciever

                  http://sites.google.com/site/sm6lkm/saqrx

                  or winrad

                  put rel 1.32 onto XP geos real well, play a sample wav thru it.


                  This site shows some tones to avoid

                  halfway thru the pages im this link

                  http://www.qsl.net/dl4yhf/speclab/vlf_rcvr.htm

                  Comment


                  • #24
                    Originally posted by simonbaker View Post
                    Tell us why you gave up. It was an interesting experiment.

                    I don't understand comment that increasing TX would decrease phase difference between targets. I would think its the opposite. Can someone explain?

                    You would need to examine all the phases of the sync pulses etc. to make sure the discrimination and GB are working as expected or whether you need some mods (probably).

                    Probably harder to tune everything at higher freq, but I say keep trying, let us know. We can try to help troubleshoot.

                    Regards,

                    -SB
                    Simon, the attached diagrams show what happens when we increase TX frequency. The diagrams are valid for soils and for targets.
                    Attached Files

                    Comment


                    • #25
                      Originally posted by mikebg View Post
                      Simon, the attached diagrams show what happens when we increase TX frequency. The diagrams are valid for soils and for targets.
                      I guess it depends on how you model the target.

                      Using the simple "coil and resistor" target model that the PI boys use in their simulations, an AC analysis seems to indicate that the phase difference between targets typically increases with frequency over a range, then decreases with frequency. So it does both!

                      Attached is the simulation. Maybe I'm not doing the right sim, or maybe its not true to life. But interesting. I'm still not clear why the phase difference gets smaller with really high frequencies; need to dig into the sim.

                      Cheers,

                      -SB
                      Attached Files

                      Comment


                      • #26
                        Originally posted by simonbaker View Post
                        I guess it depends on how you model the target.

                        Using the simple "coil and resistor" target model that the PI boys use in their simulations, an AC analysis seems to indicate that the phase difference between targets typically increases with frequency over a range, then decreases with frequency. So it does both!

                        Attached is the simulation. Maybe I'm not doing the right sim, or maybe its not true to life. But interesting. I'm still not clear why the phase difference gets smaller with really high frequencies; need to dig into the sim.

                        Cheers,

                        -SB
                        P.S. I guess on thinking about it, there is only so much phase shift a simple first order circuit (inductor-resistor or capacitor-resistor) can do, so they eventually converge to the same maximum value.

                        Comment


                        • #27
                          Hi,
                          I've been thinking about increasing the frequency for prospecting also, but I thought I'd try decreasing the inductance of the coils by half. That would increase the resonant frequencies by a factor of 2.

                          I suspect I'd need to use a slightly smaller gauge wire to satisfy other circuit parameters.

                          I need to build my circuit yet, but was wondering if anyone else has experimented with alternate inductance values and what circuit mods may've been required.

                          Thanks
                          Kev.

                          Comment


                          • #28
                            No,no,no!
                            F is proportional to 1/(square root(LC)), it's even discussed earlier in this very thread!

                            Comment


                            • #29
                              Originally posted by Skippy View Post
                              No,no,no!
                              F is proportional to 1/(square root(LC)), it's even discussed earlier in this very thread!
                              If I plug in a 3mH inductor into this formula using the standard TGSL tank caps, I get 20.5kHz, admittedly not a factor of 2 but more like 1.5

                              What do you get Skippy?

                              From what I recall, in a Colpitts osc => c = (C1.C2)/(C1+C2) no?

                              Comment


                              • #30
                                Howdy,
                                "Nothing new under the sun" "Seek and you shall find"
                                Thanks to the generous contributors on this forum the answers are already here.
                                http://www.geotech1.com/forums/showt...ghlight=diablo

                                Seems that sensitivity to small targets such as nuggets is not just a function of frequency, but also ratios of inductance between Tx and Rx coils, this is one reason why the Lobo and Diablo etc., have such large Rx coil inductance in relation to the Tx, it is a transformer boosting effect magnifying sensitivities.

                                Cheers
                                Kev.

                                Comment

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