Configurations

COMPACT CONFIGURATION with an ADALM-PLUTO – Rasperry Pi 4 – ETHERNET

Avantages	Disadvantages
– Well-known RPI4 – Wifi or Ethernet – 12 bits of Pluto dynamic	– poor stability in frequency of the Adalm-Pluto

May require the addition of an external oscillator and the extension of the Adalm-Pluto band.

COMPACT CONFIGURATION with an ADALM-PLUTO – Opi Zero 2 – Wifi

Avantages	Disadvantages
– optimized for cost – Wifi or Ethernet – 12 bits of Pluto dynamic	– poor stability in frequency of the Adalm-Pluto

May require the addition of an external oscillator and the extension of the Adalm-Pluto band.

Mixed Configuration HackRF – RTL-SDR – Orange Pi Zero 2

Avantages	Disadvantages
– optimized for cost – good frequency stability of the TX if a TCXO mounted on the HackRF One	– different frequency coverage of RX and TX – RX frequency stability depends on the chosen RTL-SDR model – 8 bits of SDR dynamic

Mixed Configuration HackRF – RTL-SDR – Raspberry Pi 4

Avantages	Disadvantages
– Well-known RPI4 – good frequency stability of the TX if a TCXO mounted on the HackRF One	– different frequency coverage of RX and TX – RX frequency stability depends on the chosen RTL-SDR model – 8 bits of SDR dynamic

Mixed Configuration HackRF – MSI.SDR (RCP1) – Raspberry Pi 4

Avantages	Disadvantages
– Well-known RPI4 – good frequency stability of the TX if a TCXO mounted on the HackRF One – HF coverage with a chinese SDR equivalent to RSP1 with a dynamic of 12 bits	– different frequency coverage of RX and TX – medium RX filtering

Mixed Configuration HackRF – SDR Play RSP1A – Raspberry Pi 4

Avantages	Disadvantages
– Well-known RPI4 – good frequency stability of the TX if a TCXO mounted on the HackRF One – HF coverage with a RSP1A and a dynamic of 14 bits	– different frequency coverage of RX and TX

Configuration 2 Hack RF One

Avantages	Disadvantages
– Well-known RPI4 – good frequency stability of the TX and RX if a TCXO mounted on the HackRF One or shared between them – large frequency coverage	– 8 bits of SDR dynamic

Configurations RTL-SDR and SA818

Avantages	Disadvantages
– cost around 100 € – power 1w HF	– VHF 2m and/or UHF 70cm only – only NBFM transmission, no SSB

Details on the one band transceiver here.

Details on the two bands transceiver here.

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 HackRF One, 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.

As of today (October 2021), the Raspberry Pi 4B (2 GB) is a good solution, but there are supply difficulties. 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.

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 link, only 220v near the transmitter / receiver.

Note that 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.

Code Source et Image

The source code and the image for Orange Pi and Raspberry Pi 4B are available on Github https://github.com/F1ATB/Remote-SDR .

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 rate reduction

An SDR like the Pluto requests 1.4 M samples / s (minimum) * 2 Bytes (16 bits) * 2 channels (I and Q) = 5.6 M Bytes / s for reception. It is the same for the emission. Which gives us more than 10M bytes / second.
With Remote SDR, output on Ethernet or WiFi requires:

• 10 k samples / s * 2 bytes for the audio in reception
• 10.24 k sample / s * 2 bytes for the received spectrum
• 10 k sample / s * 2 bytes for transmit 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 speed 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 the desktop and VNC.