WebSDR node based on a Raspberry PI

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WebSDR node based on a Raspberry PI

This WebSDR setup covers a dual band receiver (80/40 meters bands) time-based switched. It uses a relay to switch between antennas who is managed by one GPiO pin on the Raspberry PI (using a driver transistor).

Very special thanks to Pieter PA3FWM, Mark G4FPH and Jarek SQ9NFI for the helpful hand on configuring the progfreq setting.

General hardware requirements

Raspberry PI 3 or greater.
Raspberry OS 11 (bullseye) installed and working.
Internet access setup and working
RTL-SDR USB Dongle

Required setup and software

sudo apt update && sudo apt upgrade
sudo apt install -yq
  g++ \
  make \
  libsigc++-1.2-dev \
  libgsm1-dev \
  libpopt-dev \
  tcl8.5-dev \
  libgcrypt-dev \
  libspeex-dev \
  libasound2-dev \
  alsa-utils \
  libqt4-dev \
  libsigc++ \
  cmake \
  groff \
  rtl-sdr \
  libusb-1.0-0-dev \
  unzip

Missing libraries

Over the time, some required libraries were deprecated in favor of newer and incompatible versions.

libpng12

tar xf libpng-1.2.59.tar.xz
cd libpng-1.2.59/
./configure
make
sudo make install

libssl-1.0.0

tar xf openssl-1.0.0k.tar.gz
cd openssl-1.0.0k/
cat << EOF > openssl.ld
OPENSSL_1.0.0 {
    global:
    *;
};
EOF
./config shared --prefix=$HOME/libssl/openssl --openssldir=$HOME/libssl/ssl -Wl,--version-script=openssl.ld -Wl,-Bsymbolic-functions
make
sudo make install_sw
sudo ldconfig
ldd $HOME/libssl/openssl/bin/openssl
sudo cp $HOME/libssl/openssl/lib/libcrypto.so /usr/local/lib
sudo chmod 0755 /usr/local/lib/libcrypto.so
sudo ldconfig

RTL SDR direct sampling (500khz - 28.8Mhz without upconverter!)

If your SDR dongle supports direct sampling (such as RTL-SDR.com V3 receiver), there's a way to receive 500khz-28.8mhz without an external upconverter hardware, easing the node build.

unzip rtl-sdr-driver-patched.zip
cd rtl-sdr-driver-patched/
mkdir -p build/
cd build/
cmake ../ -DINSTALL_UDEV_RULES=ON -DDETACH_KERNEL_DRIVER=ON
make
sudo make install
sudo ldconfig

Don't forget to remove the progfreq line from the websdr configuration file(s).

Use the following systemd unit for direct sampling:

sudo cp etc/systemd/system/rtl_tcp_direct_sampling.service /etc/systemd/system/rtl_tcp@.service

Install WebSDR

Ask Pieter to get a copy of WebSDR.
Copy the websdr-rpi binary and files to your home directory (/home/pi/)
Edit websdr.cfg (for single band use), or websdr-80m.cfg and websdr-40m.cfg (for dual band use) to fulfill your configuration
Create Systemd units to manage websdr and rtl_tcp

sudo cp etc/systemd/system/websdr@.service /etc/systemd/system/websdr@.service

Copy this systemd unit only if you're NOT using the RTL SDR direct sampling method

sudo cp etc/systemd/system/rtl_tcp@.service /etc/systemd/system/rtl_tcp@.service

Single band WebSDR

The setup described in this section is the most usual: a single band SDR receiver (say, 40m band).

Create systemd units to manage websdr and rtl_tcp:

sudo cp etc/systemd/system/websdr.service /etc/systemd/system/websdr.service

Enable the rtl_tcp systemd unit:

sudo systemctl enable rtl_tcp@0.service

Enable the websdr unit:

sudo systemctl enable websdr.service

Time-controlled, dual band WebSDR

The setup described in this section is a more powerful one, where the Raspberry PI switches the WebSDR bands according to the time you define in crontab.

Antenna controller

This WebSDR setup uses one RTL-SDR dongle for two bands (40/80 meters), crontab takes control of which band is working. As wave length isn't the same on both two bands, I'm using a GPiO port to switch between them using a DPDT relay. GPIO3 is controlled by the check_band.sh cron script.

Enable WebSDR for dual band operation

Enable just the rtl_tcp systemd unit. Websdr is managed by crontab

sudo systemctl enable rtl_tcp@0.service

Cron

I built a crontab configuration to switch between 40m and 80m bands time-based. Just import the crontab lines into your crontab.

Manual control

You can always control band changes manual way. Disable cron lines to avoid automatic setup changes. Then you can use

sudo systemctl stop websdr@40.service
sudo systemctl start websdr@40.service

Where 40 is the band you want to receive. You can use and setup almost any band you want, as long as you had setup your websdr-{{band}}m.cfg

GPIO Setup

Copy the etc/rc.local file to your /etc/rc.local

sudo cp etc/rc.local /etc/rc.local

Check and match GPIO ports for relay control to switch antennas and a button to soft reset the Raspberry pi.

Software reset

There is a Python script that handles Raspberry PI reboots from a hardware switch without killing power.
Check the /etc/rc.local file and match the desired GPIO port for this task.
Copy lib/systemd/system/reset.service to /lib/systemd/system/reset.service

sudo cp opt/reset.py /opt/reset.py
sudo cp etc/systemd/system/reset.service /etc/systemd/system/reset.service
chmod 644 /etc/systemd/system/reset.service
systemctl enable reset.service
systemctl start reset.service

This is the software reset schematic. It has a 5v pull-up signal between a 10k resistor.

Blacklist RTL modules

You'll need to blacklist some modules in order to get rtl_tcp working. Edit or create the file /etc/modprobe.d/blacklist.conf with the following content:

blacklist dvb_usb_rtl28xxu

reynico / raspberry-websdr