Remote SDR V2

“Remote SDR” is a web application allowing to remotely control an amateur radio transceiver between 1 MHz and 6 GHZ. Its first application was the duplex control of a station allowing links to the geostationary satellite QO-100 / Es’Hail 2.

Version 2 offers new features:

  • Processing of Adalm-Pluto SDR in addition to HackRF or RTL-SDR
  • Reception in NBFM, WBFM, AM in addition to SSB
  • Transmission in NBFM or SSB
  • Spectral analysis on 2048 points instead of 1024.
  • Transmitter modulation compressor
  • CTCSS encoder
  • DTMF encoder
  • Programmable frequency shift for relays

The set is made up of:

  • a reception channel: SDR (Software Design Radio)
  • a transmission channel: SDR
  • one or 2 Orange PI or Raspberry Pi 4 single board computer for signal processing and web server
  • from a PC, a tablet, or even a smartphone, controlling everything with “Remote SDR” running on a web browser like Chrome or Edge.


Remote SDR – Adalm-Pluto – Opi One Plus


Remote SDR – Adalm Pluto –Raspberry 4


 Remote SDR – Adalm Pluto – Opi Zero 2 – Wifi

Interesting solution with the new Orange Pi Zero 2 which allows a WIFI connection to the HF part



Remote SDR – 2 HackRF One – Raspberry 4B

These configurations make it possible to locate the HF part near the antennas, which is essential for links above GHz. In the transmission chain, amplifiers must be added to bring the HF signal to the desired level as well as filtering to ensure that unwanted lines are not emitted. The SDR of the reception chain can be either an RF Hack, an RTL-SDR or a Pluto depending on the frequency band you want to cover. Not all RTL-SDR models cover the same band. The transmission reception is carried out in full-duplex which is essential during satellite connection to hear the return of its own signal.

The “Orange Pi” are processors similar to the Raspberry Pi running under the Armbian or Debian Operating System. In 2020 I used the Orange Pi One Plus, now in 2021 the Orange Pi Zero 2 also offers a 64-bit / 4-core processor, but also an ethernet or WiFi connection. They serve as a web server and perform radio signal processing. In all the configurations presented above, you can use an Orange Pi One Plus or the recent Orange Pi Zero 2.

Note: it seems that as of this day (July 2021), the Orange Pi One Plus is no longer on sale. The Orange Pi Zero 2 remains available and replace perfectly the Orange Pi One Plus. The Raspberry Pi 4 with a 2 GB memory is a good alternative.

Example Transceiver QO-100

Example UHF Transceiver – Wifi – Orange Pi Zero 2

New configuration with the Orange Pi Zero 2 which allows communication via WIFI. No more wired Ethernet connection, only 220v near the transceiver.

432 MHz Experimental Transceiver

Note , you need a USB hub between the Pluto and the Orange PI One Plus (not for the Orange Pi Zero 2). This corresponds to a system bug that I cannot explain.

Key points of Remote SDR

In addition to being able to locate the HF treatment near the antennas, other points should be noted such as:

Data Flow reduction

An SDR like the Pluto requires 1.4 M samples / s (minimum) * 2 Bytes (16 bits) * 2 channels (I and Q) = 5.6 M Bytes / s for reception. The same for the transmission. Which gives us more than 10M bytes / second.

With Remote SDR, the output on Ethernet or in Wifi requires:

  • 10 k samples / s * 2 bytes for the receiver audio
  • 10.24 k sample / s * 2 bytes for the receiver spectrum
  • 10 k samples / s * 2 bytes for transmiter audio
    We are at less than 100 k bytes / s by adding the control data.

There is therefore a reduction of approximately 100 in the communication flow required, which facilitates remote control via internet / ethernet without loss of quality through data compression.

The mini remote computer

Indeed, we have a remote computer which has a GPIO to which it is possible to add functions. For example, controlling an antenna rotor, measuring electrical voltages, temperatures, etc.. It is possible to access the system via the web (Apache server), in SSH to launch an application in terminal mode, or in graphical mode by desktop and VNC.

Source Code and Image

The source code and the image for an Orange Pi One Plus are available on Github https://github.com/F1ATB/Remote-SDR .

Posts describing Remote-SDR

Remote SDR – Raspberry Pi 4B or Orange Pi Zero 2 image installation

Raspberry 4

Remote SDR version3.0 available on Github

Orange Pi Zero 2

Here is the detailed procedure to install Remote SDR version 3 on a Raspberry Pi 4B with at least 2 GB of memory or an Orange Pi Zero 2 (1GB). The latest images written for an SD card of 16 GB or more are available on Github.

Remote SDR

Remote SDR is an application allowing remote control from a web browser of a radio transceiver based on 1 or 2 SDR (Software Design Radio).

The main features are:

  • Processing of SDRs:
    • Adalm-Pluto,
    • HackRF One,
    • RTL-SDR,
    • SA818 transmitter module in NBFM,
  • Reception in SSB, NBFM, WBFM and AM,
  • Transmission in NBFM or SSB with Pluto or HackRF One,
  • Reception spectrum on 2048 FFT points up to 2 MHz band,
  • Interfacing with Gpredict to compensate the Doppler of low orbit satellites,
  • Supply of system and SDR observation tools

Installing the image

  • Download the image corresponding to your card on Github https://github.com/F1ATB/Remote-SDR/releases
  • Unzip the image
  • Burn the image on a minimum 16GB micro SD card with PC software such as Win32diskmanager
  • Connect a Pluto or HackRF One SDR and RTL-SDR
  • Connect the Raspberry/Orange to the local Ethernet network
  • Power on the Raspberry/Orange Pi
  • Go to your box to find the IP address that has been assigned to the Raspberry/Orange Pi

Launch of Remote SDR

Only one Raspberry PI 4 is necessary with an Adalm-Pluto or a HackRF in transmission and an RTL-SDR in reception.

Rpi4 – Pluto
Rpi4 – HackRF – RTL-SDR
Two Orange Pi Zero 2

Since Remote SDR version 2.5, two HackRF One can be connected to one Raspberry 4B.

F1ATB QO-100 setup. Raspberry 4 and 2 HackRF One

You launch the application on the address:

http://<ip du Rasperry Pi>

You need a modern browser like Chrome or Edge. These do not give access to the microphone if the site does not have secure access in https. On your local network at home, you generally work in http simply. To get around this difficulty, the solution is to set up a derogation at the level of the web browser by accessing the “flags” parameters. you must type in the address bar:

with Chrome: chrome://flags

with Edge(2020): edge://flags

Look for the heading:

Insecure origins treated as secure

Fill in the form as below with the IP address of the Raspberry PI which provides the pages.

Note that the exchanges are done in http on the usual port 80 for the contents of pages. Ports 8001 to 8003 are used to exchange data with the Raspberry Pi of the reception part. Ports 8004 to 8005 are used to exchange data from the transmit part.

With version v3 of Remote SDR, it is possible to interface with Gpredict via port 8006 for the receiver and 8007 for the transmitter.

In the case of a single processor, it processes all the exchanges on ports 8001 to 8007.

Customization of the installation

The image on Github is configured in English language, GB keyboard and GMT time. Access the Raspberry/Orange Pi in ssh (user pi, password: remsdr) and type:

raspi-config or armbian-config

In the ‘Location’ section you can enter your preferences.

You can also access the Raspberry Pi in graphics mode using the VNC extension from chrome or a dedicated application.
user : pi or root for the Orange Pi
password : remsdr

All sources are in the folder /var/www/html .

Quick SDR Test

You can do a quick test to verify that the connected SDR (s) are visible to the Raspberry/Orange Pi. In a Terminal window, make a list of Usb(s ) by typing: lsusb
The devices present should appear.

Adalm-Pluto from Analog Devices connected


If you use your Remote SDR application intensely, consider putting a heat sink on the CPU. The processing load is important: around 60%.

Do not display Remote SDR on a monitor connected to the Raspberry and running in the web browser. If feasible, the processing load will be too great and this will result in audio losses and processor overheating.

Also, I recommend a transmitter security system as described here.

Video on Remote SDR V2

Posts about Remote SDR