PHYSICS

1. VLF spectrum (3 kHz – 30 kHz)

Microwaves, Cellular, and Wi-Fi services operate at gigahertz frequencies; building materials and water columns attenuate those bands strongly. By contrast, strategic and geophysical communications routinely use the Very Low Frequency (VLF) range when a path must survive earth, seawater, or large-scale conductive structures.

While higher frequencies like microwaves (GHz) can interact with surface tissue, their skin depth is limited; they are easily shielded by metal structures or salted water. For a signal to reach a target inside a Faraday cage or deep underwater, the physics necessitates the Long-Wave Regime (VLF/ELF), where shielding becomes nearly transparent.

The signal followed me into the metal tube of a high-altitude flight and even during deep cave diving. This protocol of exposure reveals a critical technical fact: Microwaves and standard cellular signals fail here. Only frequencies with extreme penetration power — matching the profiles of submarine communication (VLF) — can bypass a jet's fuselage and meters of solid, mineral-rich rock.

• Wavelength (free space): approximately 10 km – 100 km for 3 kHz – 30 kHz (λ = c/f).
• Propagation characteristic: pronounced diffraction around large obstacles and deep penetration into conductive continua (e.g. saline water, moist soil, tissue — each with its own complex permittivity and conductivity).
• Documented applications: submarine VLF/ELF shore-to-boat links, crust-scale radio sounding, and other engineered low-frequency channels where HF and microwave links are not viable.

2. Skin depth (penetration into conductors)

In a good conductor, time-harmonic fields decay exponentially with depth. The skin depth δ is the distance over which amplitude falls to roughly 1/e of its surface value (~37% of incident amplitude in amplitude terms).

Using resistivity ρ (Ω·m), angular frequency ω = 2πf, and permeability μ (H/m), a standard low-frequency form is:

ρ — electrical resistivity of the medium. ω — angular frequency. μ — magnetic permeability (often ≈ μ₀ for non-magnetic materials).

Equivalent conductivity form (σ = 1/ρ):

At a fixed material, δ grows as frequency decreases. Microwave bands (e.g. 2.4 GHz) therefore deposit energy in a thin surface layer of a good conductor or high-loss tissue, whereas at tens of kilohertz the same macroscopic object presents a much thicker electromagnetic penetration scale — a routine result in classical electrodynamics, not a special claim about any transmitter.

3. Deep-structure reception (empirical correlation)

Observation: In some underground or shielded volumes — extended cave systems, deep basements, or similar — consumer cellular (4G/5G) field strength often drops to unusable levels while other low-frequency or conducted channels may still register on a receiver, depending on installation, geology, and noise floor.

Inference (physical): If GHz-band energy cannot traverse the same rock/soil barrier at measurable power, any coherent coupling observed under those conditions is inconsistent with microwave-carried paths alone. Long-wavelength (VLF/ULF) or wired/conducted energy transfer remains within the set of physically admissible explanations and is the band engineers use when HF/microwave links fail in earth or sea.

Quantitative closure requires site-specific measurements (spectrum analyser, calibrated probes, shield topology) and documented geometry — this section states the propagation-class argument only.

4. Pulse modulation vs. EEG band structure

Carriers are rarely informative as unmodulated sine waves; envelope and pulse trains define the low-frequency content at the receiver. Clinical EEG taxonomy groups cortical rhythms into named bands (delta through beta). Any external field whose modulation spectrum overlaps those frequencies is, in principle, a candidate for time-domain interference with ongoing neural oscillations — subject to coupling efficiency, exposure limits, and tissue filtering.

Band definitions are listed in the panel below.

Band definitions are listed in the panel to the right.