Geotech Baracuda - REV-A - Coils

[Chiv]

Have finished the board with the every thing in place, tested for volts and found negative rail only getting -4.7v is that a problem? In step 7 trying to get the volts to -2.7v can not make that voltage only -1.7v now I'm thinking it because of the -4.7v supply!! After reading forum over and over I have decided to buy a oscilloscope to help with this build as my automotive oscilloscope is not good enough to dial in my coils to the barra. the barra dose pick up sig with every thing connected but only 10cm on screw driver which I'm not to concerned about until I can hook up on the oscilloscope. my main question is- dose the -4.7v rail a real problem that need to be repaired so it is a true -5v

[Chiv]

well my testing of the double figue 8 coil had come to abrupped end, Yep i let the smoke out on LT1054(U5) slipped with test pin belonging to the oscilloscope, now waiting for local shop to get a few in for me, time to build a few more coils for my vhf while I wait

[green]

I think your going to find the figure 8 coil also cancels out target signal on a PI.

You are correct. I was thinking about the null in the center and forgot about having to add an absolute value circuit to my PI, also needed when adding GEB.

[homefire]

I think your going to find the figure 8 coil also cancels out target signal on a PI.

[green]

I have started a Barracuda build so far so good with the bad shakes for soldering, I'm at the stage of building a coil to test at step 4, now with building my coils yep built lots of proto type for experiments (use the calculator) plus using the little LC100A tool for checking UH and PF. I am amazed at what sort of reading that you can get from loose windings to tight windings, from spider web coils to basket, even tried lan cable that I stripped to make 3pair twisted 10cm coil (even at 48 wraps could only get 105uh got quite fat that coil did). Now I have built a coil that is 556.9uh and 162pf from .4mm enamel coated, now if I elongate the circle to 70mm dia this bring 556uh to 476uh and 162pf to 149pf. ( to be expected ) Now If I make a figure 8 with this same coil I get487uh and 147pf, now the fun bit, if I squash the Figure 8 together and then cross the centres over to make another Figure 8 in the centre this drops UH to350uh and 105pf, now I have read in many places that a figure 8 coil self cancels itself out for emi in vlf (good for salt lakes) I'm new at this PI side of things so my question is; would a double figure 8 work on a PI set up, when you look at the lay out there is no real dead spots in the coil like a standed figure 8 coil as far as I can see, I'm interested in what other people have to say before I resin it together for a test when I finish this Barracuda

I use two round coils, one inverted to make my figure 8 coils so I maybe looking at your example wrong. I don't see the difference between your double figure 8 and one starting out with twice the turns and half the diameter and twisting for a figure 8. You can test with the coil before potting. Just swing the targets on a wood or plastic ruler. Verify the ruler doesn't cause a response without the target.

[Chiv]

I have started a Barracuda build so far so good with the bad shakes for soldering, I'm at the stage of building a coil to test at step 4, now with building my coils yep built lots of proto type for experiments (use the calculator) plus using the little LC100A tool for checking UH and PF. I am amazed at what sort of reading that you can get from loose windings to tight windings, from spider web coils to basket, even tried lan cable that I stripped to make 3pair twisted 10cm coil (even at 48 wraps could only get 105uh got quite fat that coil did). Now I have built a coil that is 556.9uh and 162pf from .4mm enamel coated, now if I elongate the circle to 70mm dia this bring 556uh to 476uh and 162pf to 149pf. ( to be expected ) Now If I make a figure 8 with this same coil I get487uh and 147pf, now the fun bit, if I squash the Figure 8 together and then cross the centres over to make another Figure 8 in the centre this drops UH to350uh and 105pf, now I have read in many places that a figure 8 coil self cancels itself out for emi in vlf (good for salt lakes) I'm new at this PI side of things so my question is; would a double figure 8 work on a PI set up, when you look at the lay out there is no real dead spots in the coil like a standed figure 8 coil as far as I can see, I'm interested in what other people have to say before I resin it together for a test when I finish this Barracuda