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  1. mgburr

    Another foray into Multi-loop Coil Antenna design

    Just for an update. I changed the values of the voltage divider for the monitoring circuit. Decreased the current by a factor of about four. My monitored voltage surge on the signal conditioner output caused by LED jump dropped from 200mvpp, to 20mvpp. And duplicated it on two other units...
  2. mgburr

    Another foray into Multi-loop Coil Antenna design

    Sounds like NAV/MAR, don't remember Army paying that much attention to things as such. I worked Navy Helicopters for 20 years. I used to have my ASEMICAP login to their resources. The biggest problem with what I'm batteling is, I didn't design it. I'm trying to debug someone elses H/W design...
  3. mgburr

    Another foray into Multi-loop Coil Antenna design

    The electronics are in enclosures, and depending on the application, may be as close as 15ft. We do see external noise from variable speed motors, CB's etc and try to mitigate those as much as possible. When we setup the transmit/receive pair the pulsed field is nulled. What we are actually...
  4. mgburr

    Another foray into Multi-loop Coil Antenna design

    VE1BLL, sorry about the typo, responded on my phone and it decided it wanted BILL instead of BLL.
  5. mgburr

    Another foray into Multi-loop Coil Antenna design

    VE1BILL, thanks for the quick look. And yes I shouldn't see any affect with the dc, however reality does intrude:). What I'm curious about is with the minor ripple from the SMPS sources sitting atop the reference voltage. Could these be setting up a small magnetic field that when current is...
  6. mgburr

    Another foray into Multi-loop Coil Antenna design

    I'm still working through some of the transmit refinement for our antenna design. I've had a chance to actually see what is being measured by using a Tektronix Spectrum Analyzer. Definitely an eye opener. Now comes another interesting question about our antenna system. If you check my...
  7. mgburr

    LF Coil antenna impedance

    Ouch, trying to keep costs down, don't have a lot of funding for the R&D department ;-) hence the raw calculator work :-D But you're right that would definitely make it easier to check the antennas out.
  8. mgburr

    LF Coil antenna impedance

    I was looking at something similar. Those will definitely help with the transmit coils. The receive section is a little harder because of the dual coil setup. i.e. CCCCCCCCCCCCCCCCCCCCCCCCCC C C C...
  9. mgburr

    LF Coil antenna impedance

    The detection uses timing pulses to enable the "look" for the magnetic decay, so the receive section is turned off during the primary pulse and the kickback pulse. The timing is critical to the detection system. Although it would be nice to increase the number of turns at a rate that is...
  10. mgburr

    LF Coil antenna impedance

    I had a chance to peruse the non-foster filters, It looks like it might work, however as noted the frequency is definitely below most of the designs presented. The reason for the original question is the documentation for the original antenna designs were incomplete. I.e. It's more of a trial...
  11. mgburr

    LF Coil antenna impedance

    That sounds like it might help. Currently we "tune" each receive antenna using a resistor network to balance the incoming signal. Active wouldn't be a bad option, and I can always change the input hardware to accomidate for that.
  12. mgburr

    LF Coil antenna impedance

    My biggest frustration though is the varying widths of the conveyors means the number of turns changes to keep the current down and not drive the circuits into overload. When we wind and antenna, we pre-pour check it to make sure it will terminate correctly and also to ensure the current is...
  13. mgburr

    LF Coil antenna impedance

    We have some more sensitive designs that use a box around the transmit and receive antennas, but they are operating around 10-14kHz. The conveyors are variable width. The reason I am looking is the antenna designs were created around 40 years ago, but nothing has been done to improve them with...
  14. mgburr

    LF Coil antenna impedance

    We manufacture Metal Detectors for Industrial applications. I.e. metal traveling down a conveyor belt. We send out a 50us pulse that has a sharp rise and drop from the inductive effect from the wire wrap antenna. Our antennas are 16ga copper and 22ga copper. The transmit antenna has about 17...
  15. mgburr

    LF Coil antenna impedance

    I'm looking for ideas or references that will help me design multi loop coil antennas for 1380Hz to 5000Hz range. The system is a transmit and receive system that puts out a bipolar pulse, and measures the Eddy current decay off of a piece of metal that passes between the antennas. I'm looking...

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