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7 votes
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Connecting two sites in the Arctic and Antarctic with a HUGE equatorial repeater? (Science fiction story advice)

Suggestion to OP (and all hams): Play with VOACAP Online to get a feeling for HF propagation. For example here is the whole path: And here is the expected probability of communication on a few ham ...
tomnexus's user avatar
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7 votes
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Why are VLF EM waves labeled as "sonic" in ARRL charts?

You're reading into it too much. It just means signals that, if you were to receive them directly, with no demodulation or frequency mixing, they would fall into (or near) the audible frequency range. ...
hobbs - KC2G's user avatar
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6 votes

Does anyone know of a compact ELF wave transmit antenna I can buy or make?

The wavelength at 1 Hz is several times greater than the circumference of the Earth. At these frequencies, one arguably can't even have an "antenna" for terrestrial communication, since any ...
Phil Frost - W8II's user avatar
5 votes
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Need a ferrite suppression material for choking 15 kHz to 60 kHz

I don't think it will work to add suppression to the fence. The fence charger is designed to support heavily reactive loads by generating pulses every second or two. The pulses are formed by dumping ...
Glenn W9IQ's user avatar
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4 votes
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Rudementary Impedance measurements for VLF antenna system

At 4 kHz you could use your laptop as a rudimentary two-channel oscilloscope. First find out if it has a useful two-channel input sound card, and find a way of recording a stereo 16-bit WAV and ...
tomnexus's user avatar
  • 11.4k
4 votes
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Designing VLF antenna

A squarish shape antenna is the best sender/receiver There is no practical basis for this assertion. Wavelength of the 15Khz [SIC] frequency is around 14990 meter [SIC] The formula for the ...
Glenn W9IQ's user avatar
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3 votes
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Estimating near-field electric field strength at LF (137 kHz)

Below is a rough estimate of the near fields calculated by NEC4.2 for an elevation of 3 meters above level Earth from a transmit antenna and system as generally described in the OP, and the followup ...
Richard Fry's user avatar
  • 2,922
3 votes

Estimating near-field electric field strength at LF (137 kHz)

Estimating the near field is best done with modeling software or empirical measurement. The details of the antenna construction and environment (the ground and any nearby conductive objects in ...
Phil Frost - W8II's user avatar
3 votes
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How to explain a frequency pic at 1.5 kHz?

display_qt is a GNU Radio example program. It does not display any actually existing electromagnetic signal but internally generates a 1500 Hz sinusoid. The code ...
Kevin Reid AG6YO's user avatar
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3 votes

Rudementary Impedance measurements for VLF antenna system

Your method only crudely measures the magnitude of the feedline impedance, without taking into account the fact that it is probably a complex value, with a phase shift between voltage and current. ...
Dave Tweed N3AOA's user avatar
2 votes

Connecting two sites in the Arctic and Antarctic with a HUGE equatorial repeater? (Science fiction story advice)

With infinite resources but real technology, how would you best connect two ideal sites in the Arctic and Antarctic with an ideal, well-equipped equatorial repeater? Skip the repeater, this calls for ...
Marcus Müller's user avatar
1 vote

What core material would offer the highest sensitivity in the design of an ELF/VLF handheld rod antenna?

Another thing to consider is the strong background noise at these frequencies, caused by thunderstorms. Your antenna only needs to be sensitive enough to measure this noise, more sensitivity makes no ...
tomnexus's user avatar
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1 vote

What core material would offer the highest sensitivity in the design of an ELF/VLF handheld rod antenna?

As said in the comments, I'm really not an expert on magnetic materials. But at ELF frequencies (3 to 30 Hz, definition of the ITU), as others have said, ferrites are unnecessarily lossy / low in $\...
Marcus Müller's user avatar
1 vote

What core material would offer the highest sensitivity in the design of an ELF/VLF handheld rod antenna?

For low frequencies and low field strengths (receiving only, similar to earth's magnetic field) you could also look into Mu metal or amorphous metals, which can have extremely high permeability. I've ...
tomnexus's user avatar
  • 11.4k
1 vote

Connecting two sites in the Arctic and Antarctic with a HUGE equatorial repeater? (Science fiction story advice)

You may have prematurely eliminated some of these options, so for the sake of completeness I'm listing everything. My first thought is that the best solution would be a fiber optic cable. We've been ...
user10489's user avatar
  • 6,485
1 vote

How the ELF-VLF background noise spectrum looks like?

You don't need a spectrum analyzer for such low frequencies, more like a very accurate voltmeter that you can record over long periods. As the antenna, you will need something huge, I recommend the ...
Jack0220's user avatar
  • 371
1 vote

What are the continuous transmissions at the lower end of the spectrum?

I want to add to Phils answer. The VLF around 3-30 kHz are used for submarine communication. From WikiPedia: VLF radio waves (3–30 kHz) can penetrate seawater to a depth of approximately 20 meters....
not2qubit's user avatar
  • 378

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