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.

• 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.