“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 single board computer for signal processing and web server
- from a PC, or even a smartphone, controlling everything with “Remote SDR” running on a web browser like Chrome or Edge.
COMPACT CONFIGURATION WITH AN ADALM-PLUTO – OPI One plus – ETHERNET
COMPACT CONFIGURATION WITH AN ADALM-PLUTO – OPI ZERO 2 – WIFI
Interesting solution with the new Orange Pi Zero 2 which allows a WIFI connection to the HF part
MIXED HACKRF AND RTL-SDR CONFIGURATION
CONFIGURATION 2 HACK RF ONE
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.
Example Transceiver QO-100
For details of this project, see the post:
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.
Note , you need a USB hub between the Pluto and the Orange PI. 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.
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 .