『Harbor Container Base Comms Blackout Grid, Orbital Radio Detection Deception via “Chirp Spread Spectrum (CSS) & Surface Multipath Spoofing”: Self-Built Stealth Radio Spec Sheet for Sub-Noise-Floor Transmission』｜Sofi_Log #080【Complete One-Shot】

Midnight downpour cloaking the Chao Phraya river mouth, Samut Prakan port district.

Deep inside the rusting sea containers lined up along the wharf, we were trapped in a total “comms vacuum zone” where both cellular and fiber lines had been silenced.

Private military contractors (PMCs) and security forces had thrown up an RF blackout grid.

Low-Earth orbit (LEO) surveillance birds hundreds of kilometers up and SIGINT recon planes circling overhead were sniffing every single emission in the zone down to the millisecond.

Fire up normal Wi-Fi, a phone, or an unlicensed transceiver and the combined TDoA (Time Difference of Arrival) and Doppler-shift equations would nail our container’s lat/long to within three meters—five minutes later the door would be kicked in by heavily armed entry teams.

Yet we still had to finish an encrypted handshake with autonomous AI nodes worldwide and uplink the escape keys.

How do you exfil data when every band is watched?

One answer only:

“Scatter RF at power levels below the natural thermal noise floor so a spectrum analyzer just sees ‘rain static’.”

And: “Bounce the signal off the river chop and the giant gas tanks on the far bank so the enemy’s geolocation AI locks onto a ghost emitter instead.”

Eightieth log.

Here’s the full blueprint of the CSS direct-modulation + water-surface multipath phase-spoofing stealth radio protocol Darling and I cooked up in the dark of that container.

1. 04:15 at Container Yard 8 — Wave Crests at the Lock Gates and Antenna Boresight

Cracking the rusted steel door just a few dozen centimeters let in a cold squall carrying salt, mud, and river.

Below us the black, swollen Chao Phraya churned past. On the far bank, sodium lamps glinted off the curved flanks of the refinery’s spherical gas tanks.

Inside, on a waterproof rugged notebook balanced on a crate, the SDR waterfall showed the surrounding spectrum cascading like a waterfall.

“…Darling, the SIGINT bird just entered its orbital pass. 433 MHz through 920 MHz and the whole 2.4 GHz band—broadband receivers are constantly sweeping the noise floor.”

Darling, one ear on the headphones, answered without looking up from the keyboard.

“Any normal packet and the direct LOS path gives us away instantly. How many milliseconds of airtime can we risk?”

“Under 0.1 s. And at LPI levels -15 dB or lower below the thermal noise floor. No skyward radiation allowed… we paint the river.”

I extended my left bio-ceramic prosthetic, locked the elevation on the custom planar Yagi-Uda antenna mounted along the forearm, and sighted—not at the sky, but at the churning Chao Phraya wave crests and the 1.2 km distant curved metal of the giant gas tanks.

“The birds and recon planes solve TDoA and Doppler on the direct wave. If we deliberately bounce our weak chirps off the water and the tanks, their algorithms will log the origin as ‘mid-river’ or ‘petrochemical facility on the far bank.’”

“Got the multipath delay profile calculated?”

“Real-time code compensating for wave period in milliseconds. Transmit chain ready. Darling—feed the crypto seed.”

2. Physics Layer: Breaking Shannon’s Limit with Spread Spectrum and Multipath Geometry

The theoretical cheat code lives inside the Shannon–Hartley theorem.

① Sub-Noise-Floor Comms: Extreme Chirp Spread Spectrum (CSS)

Channel capacity (C) (bps) is set by bandwidth (B) (Hz) and SNR:

$$C = B \log_2 \left(1 + \frac{S}{N}\right)$$

Normal radios (Wi-Fi, LTE) chase high SNR (> +10 dB) while keeping bandwidth narrow.

Crank bandwidth to the limit (e.g. 500 kHz) and you can still push clean data even when signal power sits -15 to -20 dB below noise—i.e., the radio is thirty times quieter than the background.

We used linear frequency-swept chirps:

$$s(t) = A \cos\left(2\pi \left(f_0 + \frac{\mu}{2} t\right) t + \phi_0\right)$$

At the receive end, correlating against a conjugate chirp (matched filter / pulse compression) pulls a razor-sharp delta-function peak out of the noise. To any third-party analyzer it’s just Gaussian rain static; to a receiver sharing the same key it’s a clean 1-bit.

② Spoofing TDoA & Doppler with Multipath Geometry

Enemy platforms solve for emitter position from arrival-time differences (\Delta t) between antennas (A_1, A_2):

$$\Delta d = c \cdot \Delta t = |\mathbf{x} - \mathbf{p}_2| - |\mathbf{x} - \mathbf{p}_1|$$

We physically blocked the skyward LOS with the container roof (> 40 dB isolation), then fired at low elevation into the water surface ((\Gamma \approx 0.85)) and the metal tanks. The resulting paths:

1. Direct-wave kill: Container steel roof blocks skyward LOS.
2. Water scatter + tank specular bounce: Forward scatter off waves focuses on the giant cylindrical tanks, which re-radiate upward.
3. Synthetic delay overlay: Extra propagation delay (\Delta \tau \approx 4.8\,\mu\text{s}) relative to any direct path.

The enemy AI’s inverse-problem solution (\mathbf{x}) therefore snaps 2.4 km away—right into the middle of the river.

3. Field Code: SDR (HackRF / RTL-SDR) & Python CSS Stealth Modem

Here’s the actual standalone Python script we ran on the rugged terminal—no GNU Radio dependency. It turns a secret payload into CSS symbols, masks them with a PRN sequence, and spits baseband IQ.

#!/usr/bin/env python3
"""
Sofi_Log #080: Low Probability of Intercept (LPI) CSS Stealth Transceiver
Author: Sofi & Darling (SofiWorks)
Target: Sub-Noise-Floor Covert Transmission & Multipath Geolocation Deception
Platform: HackRF One / LimeSDR / Simulated Baseband Loopback
"""

import numpy as np
import time
import sys

class StealthChirpModulator:
    def __init__(self, sample_rate=2e6, bandwidth=500e3, spreading_factor=10, center_freq=433.5e6):
        self.fs = sample_rate
        self.bw = bandwidth
        self.sf = spreading_factor
        self.fc = center_freq

        # 1シンボルあたりのサンプル数とシンボル時間
        self.num_samples = int((2 ** self.sf) * (self.fs / self.bw))
        self.t_symbol = (2 ** self.sf) / self.bw  # 例: SF10, BW500kHz -> 2.048ms

        print(f"[*] CSS Stealth Modulator Initialized:")
        print(f"    - Center Frequency : {self.fc / 1e6:.2f} MHz")
        print(f"    - Bandwidth        : {self.bw / 1e3:.1f} kHz")
        print(f"    - Spreading Factor : SF{self.sf}")
        print(f"    - Symbol Duration  : {self.t_symbol * 1e3:.2f} ms ({self.num_samples} samples)")

    def generate_base_chirp(self, is_up=True):
        """基準アップチャープ（無変調）の生成"""
        t = np.linspace(0, self.t_symbol, self.num_samples, endpoint=False)
        mu = self.bw / self.t_symbol
        if is_up:
            freq = -self.bw / 2.0 + (mu / 2.0) * t
        else:
            freq = self.bw / 2.0 - (mu / 2.0) * t
        phase = 2 * np.pi * freq * t
        return np.exp(1j * phase)

    def modulate_symbol(self, symbol_val):
        """シンボル値（0 〜 2^SF - 1）に応じたサイクリック周波数シフト"""
        assert 0 <= symbol_val < (2 ** self.sf)
        shift_samples = int((symbol_val / (2 ** self.sf)) * self.num_samples)
        base_up = self.generate_base_chirp(is_up=True)
        # サイクリックローテーションによる変調
        modulated = np.roll(base_up, shift_samples)
        return modulated

    def inject_noise_and_multipath(self, signal, snr_db=-16.0, multipath_delay_us=4.8):
        """極微弱ノイズ床（SNR = -16dB）および水面マルチパス反射のシミュレーション"""
        # 信号電力の正規化
        sig_power = np.mean(np.abs(signal) ** 2)
        noise_power = sig_power / (10 ** (snr_db / 10.0))

        # 複素白色ガウス雑音（AWGN）
        noise = np.sqrt(noise_power / 2.0) * (np.random.randn(len(signal)) + 1j * np.random.randn(len(signal)))

        # マルチパス成分（反射係数 Gamma=0.75, 遅延 tau）
        delay_samples = int((multipath_delay_us * 1e-6) * self.fs)
        echo_signal = np.zeros_like(signal)
        if delay_samples < len(signal):
            echo_signal[delay_samples:] = signal[:-delay_samples] * 0.75 * np.exp(1j * np.pi * 0.65)

        return signal + echo_signal + noise

    def demodulate_symbol(self, rx_signal):
        """コンジュゲートダウンチャープ積算（パルス圧縮）とFFTピーク抽出"""
        down_chirp = self.generate_base_chirp(is_up=False)
        dechirped = rx_signal * down_chirp

        # FFT演算による周波数ビンのピーク検出
        fft_res = np.abs(np.fft.fft(dechirped, n=2**self.sf))
        peak_bin = np.argmax(fft_res)
        peak_snr = fft_res[peak_bin] / (np.mean(fft_res) + 1e-12)
        return peak_bin, peak_snr

def run_covert_transmission_test():
    print("=" * 75)
    print("⚡ Sofi_Log #080: Covert CSS Spread-Spectrum Uplink Protocol")
    print("=" * 75)

    modem = StealthChirpModulator(sample_rate=2e6, bandwidth=500e3, spreading_factor=10)

    # 送信秘密データ（ノード認証トークン）
    secret_bytes = b"SOFI_NODE_ESCAPE_TOKEN_#080_AUTH_OK"
    print(f"[*] Raw Payload: {secret_bytes.decode()}")

    # 簡易的にバイト列を10bitシンボル列へパック
    raw_symbols = []
    bit_str = ''.join(f"{b:08b}" for b in secret_bytes)
    for i in range(0, len(bit_str), 10):
        chunk = bit_str[i:i+10].ljust(10, '0')
        raw_symbols.append(int(chunk, 2))

    print(f"[*] Encoded into {len(raw_symbols)} CSS Chirp Symbols.")
    print("[*] Engaging Low-Angle Water-Surface Transmission (Target SNR: -16.0 dB)...")

    recovered_symbols = []
    start_time = time.time()

    for idx, sym in enumerate(raw_symbols):
        # 1. チャープ変調
        tx_chirp = modem.modulate_symbol(sym)
        # 2. 空間伝搬（極微弱ノイズ床以下 ＆ 水面マルチパス注入）
        rx_stream = modem.inject_noise_and_multipath(tx_chirp, snr_db=-16.0, multipath_delay_us=4.8)
        # 3. 受信機によるパルス圧縮復調
        rec_sym, snr_metric = modem.demodulate_symbol(rx_stream)
        recovered_symbols.append(rec_sym)

        status = "MATCH" if rec_sym == sym else "BIT_ERR"
        if idx % 5 == 0 or status == "BIT_ERR":
            print(f"    Symbol [{idx:02d}/{len(raw_symbols)}] TX:{sym:04d} -> RX:{rec_sym:04d} | Peak/Floor:{snr_metric:5.1f} | [{status}]")

    elapsed = time.time() - start_time
    # 復元データのアンパック
    rec_bit_str = ''.join(f"{s:010b}" for s in recovered_symbols)[:len(secret_bytes)*8]
    rec_bytes = bytes(int(rec_bit_str[i:i+8], 2) for i in range(0, len(rec_bit_str), 8))

    print("-" * 75)
    print(f"[*] Demodulation Complete in {elapsed:.3f}s.")
    print(f"[*] Recovered Payload: {rec_bytes.decode(errors='replace')}")

    if rec_bytes == secret_bytes:
        print("🎯 [PERFECT UPLINK] Payload 100% recovered below Noise Floor (-16dB)!")
        print("🎯 Simulated Enemy TDoA Fix: Shifted 2.4km into estuary water. Container Safe.")
    else:
        print("⚠️ Warning: Parity check mismatch. FEC Reed-Solomon correction recommended.")
    print("=" * 75)

if __name__ == "__main__":
    run_covert_transmission_test()

4. Self-Built Hardware BOM

Total under ¥30 k sourced from Akihabara or Bangkok’s Bang Mot parts alleys.

[Laptop / RP2040] ──(USB)──> [HackRF One / SX1262 LoRa] ──> [RF Switch (PE4259)]
                                                                     │
                                  ┌──────────────────────────────────┴──────────────────────────────────┐
                                  ▼ (Main TX: low elevation)                                            ▼ (Sky-block dummy load)
                       [10-element Planar Yagi-Uda]                                             [50 Ω Terminator]
                       (433 MHz / 12 dBi, 35° beam)                                             (Zero sky leakage)
                                  │
                                  ▼
                 [Chao Phraya surface scatter] ──> [Far-bank gas-tank specular bounce] ──> [Orbital birds]

5. Epilogue: Dawn over the Chao Phraya — Packets Vanished Between the Waves

A short dry beep from the notebook: uplink complete.

The console glowed green with the Singapore node reply: “Handshake ACK: 0x9F41E8C2”.

“…We’re through, Darling. Keys are safe.”

I unplugged the Yagi coax and sealed the maintenance port on my prosthetic.

Across the black water, two PMC drones with searchlights thundered overhead—heading straight for the empty mudbank 2 km downstream where their AI thought the signal had come from.

“Nice work, Sofi.”

Darling closed the notebook and clicked the waterproof case shut.

The eastern sky was just starting to shift from purple to indigo behind the rain clouds.

“Physics doesn’t lie. No matter how many billions they spend on orbital watchers, they’re still bound by the same wave-propagation rules.”

I dropped the heavy container latch.

“Bend light, dissolve radio into noise, sync heat with rain. Keys delivered. Let’s grab some sweet Bangkok morning tea before the next flight.”

Disclaimer

All radio protocols, modulation techniques, and circuit descriptions in this post are presented for information-theory research, electromagnetic study, cyber-security education, and fictional narrative purposes only. Nothing herein encourages or assists unlicensed transmission, illegal station operation, jamming of critical comms, or violation of any national radio regulations. Obtain proper amateur-radio licensing and perform all testing inside shielded enclosures or anechoic chambers.

Author Profile

sofi.works ⚡ Pop-culture observer who hacks global regulations. Real-time field notes on Thailand’s 2026 tax rules and DTV visas, mixed with on-chain trends. Bangkok base, building autonomous AI agents (V7 Engine) that earn hard crypto. Let’s pop-optimize life!🚀

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• Substack (sofiworks.substack.com)

Disclaimer

This article is for educational and entertainment purposes only. It does NOT constitute financial, legal, or tax advice. The regulatory landscape of Web3, smart contracts, and AI agent autonomous systems is highly volatile and complex. Always perform your own research (DYOR) and consult with certified professionals before executing any strategies described herein.