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Gary
You said: "I was Curious so I changed my detector and put the 300 ohm twin lead on it. But It Didn't seem to affect the Sensiivity at all."
You would not see any increase in sensitivity until you hit the wall of the coil locking up at or near the lowest delay you can set on your PI delay control. So, in order to see any improvements in delay, you need to reduce the range of minimum dead time (also called main delay time) by reducing a resistance and/or capacitance value to see if reducing the capacitance of the cable, about 100 pf, will render any improvements. Just reducing the cable capacitance or reducing total TX circuit seen capacitance will not produce any changes until you make the circuit operate at a lower delay to use the potential speed of a lower capacitance coil/cable.
My own crude tests show that for each 100 pf reduction in capacitance, you can gain about 1uS in speed improvement. I need to do some more work in this area to see if it is linear or what? Anyone have any ideas? So push your circuit to go down to 6 or 7uS and see if any of your coils lock up (while waving a target under the coil). If they do, you have reached their lower limit and a reduction of total TX circuit seen capacitance will produce results that you can see. Remember, reducing capacitance means increasing the damping resistor value to reflect a lower capacitance in the TX circuit. Let us know if you try this and the values you tweaked on you design?
bbsailor
You said: "I was Curious so I changed my detector and put the 300 ohm twin lead on it. But It Didn't seem to affect the Sensiivity at all."
You would not see any increase in sensitivity until you hit the wall of the coil locking up at or near the lowest delay you can set on your PI delay control. So, in order to see any improvements in delay, you need to reduce the range of minimum dead time (also called main delay time) by reducing a resistance and/or capacitance value to see if reducing the capacitance of the cable, about 100 pf, will render any improvements. Just reducing the cable capacitance or reducing total TX circuit seen capacitance will not produce any changes until you make the circuit operate at a lower delay to use the potential speed of a lower capacitance coil/cable.
My own crude tests show that for each 100 pf reduction in capacitance, you can gain about 1uS in speed improvement. I need to do some more work in this area to see if it is linear or what? Anyone have any ideas? So push your circuit to go down to 6 or 7uS and see if any of your coils lock up (while waving a target under the coil). If they do, you have reached their lower limit and a reduction of total TX circuit seen capacitance will produce results that you can see. Remember, reducing capacitance means increasing the damping resistor value to reflect a lower capacitance in the TX circuit. Let us know if you try this and the values you tweaked on you design?
bbsailor
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