Orange Pi Zero 3Complete SDR IP Server

After nearly one year of kernel crashes, WiFi driver panics, and instability, this configuration has proven rock-solid for 24/7 SDR server operation on the Orange Pi Zero 3 (Allwinner H618 SoC).

The design goal: a compact, low-power, fully headless SDR server accessible entirely over the network — including from an Android smartphone, with no desktop PC required for day-to-day operation.

Main Board & Power

SDR Receivers

RF Switch — HMC241 (Analog Devices GaAs SP4T)

The Airspy Discovery HF+ is connected through an HMC241 GaAs MMIC SP4T switch, allowing SpyServer to select between 4 antennas via 2 GPIO pins.

GPIO Truth Table — Antenna Selection

Antennas

RF Filtering & Chokes

• LPF
  30 MHz Low-Pass Filter
  Protects HF from VHF/UHF overload
• FILTER
  FM Notch Filter
  Eliminates 88-108 MHz FM overload
• CHOKE
  Toroid Chokes
  Common-mode suppression on coax
• CHOKE
  Spiral Cable Chokes
  Feed point common-mode suppression

Install Legacy Kernel

sudo apt install linux-image-legacy-sunxi64 linux-dtb-legacy-sunxi64
sudo reboot
uname -r   # Expected: 6.6.75-legacy-sunxi64

Package Repositories

All decoders run simultaneously on the same hardware. Grouped by band and protocol type:

HF Decoders

VHF / Marine / Aviation

Digital Voice

IoT & Sensors

Satellite & Radiosonde

SDR++Brown Exclusive

1 — RTL-SDR DVB Module Blacklist

Linux loads DVB-T drivers for RTL-SDR dongles by default. Blacklist them:

blacklist dvb_usb_rtl28xxu
blacklist rtl2832
blacklist rtl2830
install dvb_usb_rtl28xxu /bin/true
install rtl2832 /bin/true
sudo update-initramfs -u && sudo reboot

2 — Disable WiFi & Bluetooth (aw859a)

The H618 WiFi driver causes kernel instability. Mask and blacklist completely:

sudo systemctl mask aw859a-wifi.service
sudo systemctl mask aw859a-bluetooth.service
# Add to /etc/modprobe.d/wifi-blacklist.conf:
blacklist sprdwl_ng
blacklist uwe5622_bsp_sdio
blacklist panfrost

3 — CPU Governor: schedutil

Default 'performance' governor keeps CPU at max. schedutil scales dynamically. Temperature dropped ~8-10°C.

echo schedutil | sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
sudo sed -i 's/^GOVERNOR=.*/GOVERNOR=schedutil/' /etc/default/cpufrequtils
sudo sed -i 's/^ENABLE=false/ENABLE=true/' /etc/default/cpufrequtils

4 — USB Autosuspend (Critical for SDR Dongles)

Without this, USB dongles enter sleep and become unresponsive. Add to /boot/armbianEnv.txt extraargs:

usbcore.autosuspend=-1

5 — Disable Unnecessary Services

sudo systemctl disable --now exim4
sudo truncate -s 0 /var/log/exim4/paniclog
sudo systemctl mask systemd-networkd-wait-online
sudo systemctl mask systemd-networkd-wait-online@.service
sudo systemctl mask alsa-utils.service
sudo systemctl mask fake-hwclock.service

6 — SoapySDR / SpyServer Library Conflict

# Copy working version from /usr/local to system path
sudo cp /usr/local/lib/SoapySDR/modules0.8/libairspyhfSupport.so \
        /usr/lib/SoapySDR/modules0.8/libairspyhfSupport.so

# Lock BOTH files — apt can never overwrite them
sudo chattr +i /usr/lib/SoapySDR/modules0.8/libairspyhfSupport.so
sudo chattr +i /usr/local/lib/SoapySDR/modules0.8/libairspyhfSupport.so

# Verify — look for 'i' in the output
lsattr /usr/lib/SoapySDR/modules0.8/libairspyhfSupport.so
# Expected: ----i---------e------- .../libairspyhfSupport.so

To update the library manually in the future:

sudo chattr -i /usr/lib/SoapySDR/modules0.8/libairspyhfSupport.so
# ... make changes, then re-lock:
sudo chattr +i /usr/lib/SoapySDR/modules0.8/libairspyhfSupport.so

The HMC241 is controlled by two GPIO pins. A Python script selects the active antenna — callable from SpyServer or the SSH Button Android app.

Python GPIO Control

import OPi.GPIO as GPIO

GPIO.setmode(GPIO.SUNXI)
CTRL_A = 'PA6'   # Adjust to your wiring
CTRL_B = 'PA7'   # Adjust to your wiring
GPIO.setup(CTRL_A, GPIO.OUT)
GPIO.setup(CTRL_B, GPIO.OUT)

def select_antenna(port):  # port = 1, 2, 3 or 4
    GPIO.output(CTRL_A, port & 1)
    GPIO.output(CTRL_B, (port >> 1) & 1)

SpyServer Config

bind_host = 0.0.0.0
bind_port = 5432
list_in_directory = 1

Complete operation from an Android smartphone. Every function of the SDR server is accessible without touching a desktop computer.

1 — Flash Armbian Trixie Image

Download the Armbian 13 (Trixie) image for Orange Pi Zero 3 from armbian.com. Choose the Debian Trixie variant — not Ubuntu.

# Write to SD card (replace /dev/sdX with your card)
dd if=Armbian_26.x_Orangepizero3_trixie_*.img of=/dev/sdX bs=4M status=progress
sync

2 — Install Legacy Kernel + DTB (CRITICAL)

# Install legacy kernel AND DTB together — never one without the other
sudo apt update
sudo apt install linux-image-legacy-sunxi64 linux-dtb-legacy-sunxi64

# Remove current kernel to prevent accidental boot into wrong kernel
sudo apt remove linux-image-current-sunxi64

# Reboot into legacy kernel
sudo reboot

# Verify after reboot
uname -r
# Expected: 6.6.75-legacy-sunxi64

⚠ After first boot, immediately disable WiFi and BT drivers. → See Section 06, Tweak 2: Disable WiFi & Bluetooth

⚠ Set USB autosuspend and CPU governor. → See Section 06, Tweaks 3 & 4

⚠ Disable unnecessary services. → See Section 06, Tweak 5

3 — Verify Armbian Sources (Trixie)

Armbian Trixie repo is pre-configured in the image. Verify it is correct:

cat /etc/apt/sources.list.d/armbian.sources
# Should show: Suites: trixie

4 — RTL-SDR Blog V4 Drivers

Do NOT use the Debian repo rtl-sdr package — install from RTL-SDR Blog source for V4 support:

⚠ After installing, apply the DVB blacklist. → See Section 06, Tweak 1: RTL-SDR DVB Module Blacklist

sudo apt install libusb-1.0-0-dev git cmake
git clone https://github.com/rtlsdrblog/rtl-sdr-blog
cd rtl-sdr-blog && mkdir build && cd build
cmake ../ -DINSTALL_UDEV_RULES=ON
make && sudo make install
sudo cp ../rtl-sdr.rules /etc/udev/rules.d/
sudo ldconfig
sudo udevadm control --reload-rules && sudo udevadm trigger
# Add user to plugdev group
sudo usermod -aG plugdev $USER

5 — SoapySDR + Airspy HF+ Support

⚠ After installing, immediately apply the library lock. → See Section 06, Tweak 6: SoapySDR / SpyServer Library Conflict

sudo apt install soapysdr-tools libsoapysdr-dev soapy-connector
sudo apt install soapysdr-module-airspyhf
# Verify Airspy HF+ is detected:
SoapySDRUtil --find
# Should show: airspyhf

6 — OpenWebRX+ Installation

# Add OpenWebRX repo
wget -O - https://repo.openwebrx.de/debian/key.gpg | sudo apt-key add -
echo "deb https://repo.openwebrx.de/debian/ bookworm main" | \
  sudo tee /etc/apt/sources.list.d/openwebrx.list

# Add OpenWebRX Plus (luarvique fork — more decoders)
wget -O - https://luarvique.github.io/ppa/openwebrx-plus.gpg | \
  sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/openwebrx-plus.gpg
echo "deb [signed-by=/etc/apt/trusted.gpg.d/openwebrx-plus.gpg] \
  https://luarvique.github.io/ppa/trixie ./" | \
  sudo tee /etc/apt/sources.list.d/openwebrx-plus.list

sudo apt update && sudo apt install openwebrx

7 — OpenWebRX+ External Decoder Plugins

These are the external decoder tools OpenWebRX+ uses in the background. Install all for full decoder support:

sudo apt install \
  dump1090-fa-minimal \
  dump978-fa-minimal \
  dumphfdl \
  dumpvdl2 \
  acarsdec \
  libacars2 \
  multimon-ng \
  redsea \
  csdr-skimmer \
  sonde-decoders \
  faad \
  direwolf

8 — SpyServer Installation

⚠ Make sure the SoapySDR library fix is applied BEFORE starting SpyServer. → See Section 06, Tweak 6

# Create directory and download binary
mkdir ~/spyserver_arm64 && cd ~/spyserver_arm64
wget https://airspy.com/downloads/spyserver-arm64.tgz
tar xvf spyserver-arm64.tgz
chmod +x spyserver

# Create config file
cat > spyserver.config << 'EOF'
bind_host = 0.0.0.0
bind_port = 5432
list_in_directory = 1
owner_name =
owner_email =
EOF

# Create systemd service
sudo tee /etc/systemd/system/spyserver.service << 'EOF'
[Unit]
Description=SpyServer for Airspy HF+
After=NetworkManager-wait-online.service

[Service]
User=sdruser
WorkingDirectory=/home/sdruser/spyserver_arm64
ExecStart=/home/sdruser/spyserver_arm64/spyserver \
    /home/sdruser/spyserver_arm64/spyserver.config
StandardOutput=append:/home/sdruser/spyserver_arm64/spyserver.log
StandardError=append:/home/sdruser/spyserver_arm64/spyserver.err

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload
sudo systemctl enable spyserver

9 — rtl_tcp Services

Two separate rtl_tcp instances — one for RTL-SDR V4 (general), one for ADS-B. They conflict with radiosonde since all use the RTL-SDR hardware.

# RTL-SDR V4 service (device index 1)
sudo tee /etc/systemd/system/rtl_tcp.service << 'EOF'
[Unit]
Description=RTL-SDR TCP Server
After=network.target
Conflicts=radiosonde.service

[Service]
Type=simple
ExecStart=/usr/local/bin/rtl_tcp -a 0.0.0.0 -p 8091 -d 1 -s 2048000 -b 30
User=sdruser
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target
EOF

# ADS-B RTL-SDR service (device index 0)
sudo tee /etc/systemd/system/rtl_tcp_adsb.service << 'EOF'
[Unit]
Description=RTL-SDR ADSB TCP Server
After=network.target

[Service]
Type=simple
ExecStart=/usr/local/bin/rtl_tcp -a 0.0.0.0 -p 8092 -d 0 -s 2048000 -b 30
User=sdruser

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload

10 — Radiosonde auto_rx Installation

cd ~
git clone https://github.com/projecthorus/radiosonde_auto_rx
cd radiosonde_auto_rx

# Create Python virtualenv
python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt
deactivate

# Create systemd service
sudo tee /etc/systemd/system/radiosonde.service << 'EOF'
[Unit]
Description=Radiosonde Auto RX
After=network.target
Conflicts=rtl_tcp.service

[Service]
Type=simple
User=sdruser
WorkingDirectory=/home/sdruser/radiosonde_auto_rx/auto_rx
ExecStart=/home/sdruser/radiosonde_auto_rx/venv/bin/python3 auto_rx.py
Restart=no
TimeoutStopSec=10
KillMode=control-group

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload

11 — RF Switch Script (rf_setter.py)

Uses gpioset from libgpiod — no Python GPIO library needed. GPIO pins: gpiochip0, pins 72 and 79.

cat > /home/sdruser/rf_setter.py << 'EOF'
import sys
import subprocess

def menu():
    print("\n=== RF SWITCH MENU ===")
    print("1. Quadrifilar Helix 145 MHz")
    print("2. 9:1 Unun (Random Wire HF)")
    print("3. V-Dipole 137 MHz")
    print("4. YouLoop (HF)")
    print("5. OWon  (OpenWebRX mode)")
    print("6. OWoff (SpyServer mode)")
    print("======================")
    return input("Select: ").strip()

if len(sys.argv) < 2:
    secim = menu()
else:
    secim = sys.argv[1].strip()

komut = []
rf_ismi = ""

if secim in ("1", "0"):
    komut = ["gpioset", "-t", "0", "-c", "gpiochip0", "72=0", "79=0"]
    rf_ismi = "Quadrifilar Helix"
elif secim == "2":
    komut = ["gpioset", "-t", "0", "-c", "gpiochip0", "72=1", "79=0"]
    rf_ismi = "9:1 Unun (Random Wire)"
elif secim == "3":
    komut = ["gpioset", "-t", "0", "-c", "gpiochip0", "72=0", "79=1"]
    rf_ismi = "V-Dipole 137 MHz"
elif secim == "4":
    komut = ["gpioset", "-t", "0", "-c", "gpiochip0", "72=1", "79=1"]
    rf_ismi = "YouLoop"
elif secim == "5":
    komut = ["bash", "/home/sdruser/OWon.sh"]
    rf_ismi = "OpenWebRX mode activated"
elif secim == "6":
    komut = ["bash", "/home/sdruser/OWoff.sh"]
    rf_ismi = "SpyServer mode activated"
else:
    print("Invalid selection!")
    sys.exit(1)

try:
    subprocess.run(komut, check=True)
    print(f"OK: {rf_ismi}")
except subprocess.CalledProcessError as e:
    print(f"Error: {e}")
EOF

# Install libgpiod tools (required for gpioset)
sudo apt install gpiod

12 — Mode Switching Scripts (OWon / OWoff)

Airspy HF+ can only be used by one application at a time — either OpenWebRX or SpyServer. These scripts handle the switching:

# OWon.sh — Switch to OpenWebRX mode
cat > /home/sdruser/OWon.sh << 'EOF'
#!/bin/bash
sudo systemctl stop spyserver
sudo systemctl start rtl_tcp
sudo systemctl start rtl_tcp_adsb
sudo systemctl start openwebrx
echo "OpenWebRX activated, SpyServer stopped, RTL-TCP servers started."
EOF
chmod +x /home/sdruser/OWon.sh

# OWoff.sh — Switch to SpyServer mode
cat > /home/sdruser/OWoff.sh << 'EOF'
#!/bin/bash
sudo systemctl stop openwebrx
sudo systemctl start rtl_tcp
sudo systemctl start rtl_tcp_adsb
sudo systemctl start spyserver
echo "SpyServer activated, OpenWebRX stopped, RTL-TCP servers started."
EOF
chmod +x /home/sdruser/OWoff.sh

• Flash Armbian 13 (Trixie) to SD/eMMC
• Install legacy kernel: linux-image-legacy-sunxi64 ← MOST CRITICAL
• Blacklist DVB/RTL-SDR conflicting kernel modules
• Mask aw859a-wifi and aw859a-bluetooth services
• Blacklist sprdwl_ng, uwe5622_bsp_sdio, panfrost
• Add usbcore.autosuspend=-1 to armbianEnv.txt ← CRITICAL
• Set CPU governor to schedutil, enable cpufrequtils
• Disable exim4 and mask networkd-wait-online
• Install RTL-SDR drivers from RTL-SDR Blog repo (not Debian)
• Install SoapySDR + Airspy HF+ support module
• Fix and lock libairspyhfSupport.so with chattr +i ← CRITICAL
• Deploy SpyServer binary, configure port 5432
• Wire HMC241 RF switch: CTRL_A/B to GPIO, power from 3.3V
• Configure rtl_tcp on ports 1234 and 1235
• Install OpenWebRX+ and Radiosonde auto_rx
• Set up SSH Button on Android for antenna switching
• Test all clients: SDR++Brown, SDRAngel, Samsung Browser

This entire SDR server setup — from diagnosing kernel crashes to fixing the SoapySDR library conflict, optimizing system services, and writing this guide — was developed collaboratively with Claude, the AI assistant by Anthropic.