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I want to check the EM pulse between 3HZ-3kHZ with N9041B UXA Signal Analyzer,it seemed the only antenna I can use is Aaronia MagnoTRACKER,but the price is not affordable.

enter image description here

Then I plan to make ELF-ULF antenna myself,could you pls give me some thought to start with?

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    $\begingroup$ Sounds like an XY problem. The antenna cost is a rounding error on the N9041B analyser. What signals are you hoping to receive - natural background from the earth and sun, or artificial signals, like a mine rescue system, etc? $\endgroup$
    – tomnexus
    Sep 29, 2021 at 15:27
  • $\begingroup$ Those two cylinders likely house ferrite loop antennas. $\endgroup$ Sep 30, 2021 at 13:50
  • $\begingroup$ @tomnexus,ELF-ULF natural background pulse. $\endgroup$
    – kittygirl
    Oct 4, 2021 at 21:20

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Years ago I used a simulation like this one for the same purpose.

The antenna you refer to is a tuned antenna, so it is not wideband. The antenna that I made is a wideband, really flat response (conversion from field strength to output voltage is frequency-independent).

Conclusion: the difficulty is the design of the low-noise amplifier. Depending on what you want to measure (strong signal or low-level signal in the noise) you can use a ferroceptor with many windings and loaded with 50 Ohm (not sensitive but doing the job) up to a large loop antenna with a transformer and a low-noise amplifier.

When you are used to a simulator with noise analysis: the basic model added can help you with a quick start. F Sessinkenter image description here

Forgot to say: dimensions in meters.....

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If you need calibrated output then you probably won't be able to do it. That's why they are so expensive. It's like a \$20 SDR dongle versus a \$2,000 spectrum analyzer, with the most notable difference being that the spectrum analyzer is calibrated and tells you how much power is at each frequency. If you don't need calibrated output and just want to get a pretty good feel of what's there, then you should totally build your own antenna.

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  • $\begingroup$ $20 SDR dongle versus a $2,000 spectrum analyzer,why SDR dongle has less accuracy with less components? $\endgroup$
    – WhiteGirl
    Feb 11, 2022 at 13:03
  • $\begingroup$ The SDR looks at many frequencies at the same time and does some math on it, the spectrum analyzer only looks at one frequency at a time and does a very accurate power measurement on it, so it scans all the frequencies and plots the power. It is built for that purpose whereas the SDR is more for listening for stuff. Spectrum analyzer you're supposed to send it in every few years to recalibrate, but SDR nobody cares. $\endgroup$
    – Jack0220
    Jun 22, 2022 at 15:48
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You can utilize trees as natural antennas to capture ULF signals. This approach is supported by research conducted by Fraser-Smith, A.C. in the study titled "ULF tree potentials and geomagnetic pulsations," published in Nature, Vol 271, pages 641–642 (1978). The author has a copy on their website (archive.org memento of the same).

This method could be a cost-effective alternative to expensive large-scale antennas for detecting ELF-ULF signals.

Experimenting with this method and adjusting based on your findings could be a fascinating project. We'd love to hear about your experiments and results in detecting ELF-ULF signals using this unique approach. Please do share your experiences and findings with the community once you've conducted your exploration.

Summary of the article by chatGPT:

The article introduces a novel method for measuring ultra-low-frequency (ULF) geomagnetic pulsations using trees as antennas, a simpler alternative to traditional, complex equipment. By inserting pairs of electrodes into trees, researchers found that tree potentials can detect ULF pulsations, revealing that these signals are induced by geomagnetic field fluctuations rather than originating from the trees themselves. This discovery suggests a potential link between geomagnetic activity and biological effects on trees, such as growth, which could be influenced by natural phenomena like solar cycles or human-induced electromagnetic fields. Conducted alongside conventional equipment at Stanford University, the study demonstrated nearly identical pulsation measurements between the tree-based method and traditional solenoid antennas, confirming the viability of using trees as natural, living antennas for geomagnetic research. This approach not only simplifies the detection of geomagnetic pulsations but also opens up new avenues for exploring the interaction between geomagnetic fields and biological processes in trees, potentially offering insights into environmental influences on tree physiology and growth patterns.

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    $\begingroup$ Hello @almazaliev and welcome. I took a quick look at the link (no free PDF); it looks like the idea is to use trees as naturally occurring low-impedance ground rods (instead of driving your own rods). If you have access to the article, please could you add a summary of the method and results here so it makes a complete answer. $\endgroup$
    – tomnexus
    Feb 7 at 14:54
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    $\begingroup$ OK, I'm working through publications that follow this one, and there's actually an Ukrainian one that spells out what I suspect: Fraser-Smith build a single-turn loop antenna with a resistive tree section. Even simple considerations from basics EM theory yield that a tree, being several orders of magnitude smaller than ELF wavelengths, has little to no effect on the local homogenity of the electric field around the trunk; the tree is not an important part of the antenna: any non-conductive mast carrying two plates of a capacitor would work just as well for detecting ULF/ELF. $\endgroup$ Feb 7 at 19:39
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    $\begingroup$ Here's the original paper, О «ДРЕВЕСНОЙ» ВЕРТИКАЛЬНОЙ ЭЛЕКТРИЧЕСКОЙ СНЧ-АНТЕННЕ (Ukrainian), "About the "wood" vertical electric ULF/ELF antenna" and because I don't read Ukrainian, I had to use translate.google.com 's "Document translation", which worked surprisingly well. (careful when it translates band abbreviations – ULF, VLF are different things, but this also differs across regions) $\endgroup$ Feb 7 at 19:42

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