Langstone Project
The Langstone project is an all mode Microwave transceiver covering bands from 70MHz to 5.7GHz running on a Raspberry Pi4 and the Adalm Pluto.
The project started life as an early prototype for the Hayling project and is named Langstone as it is on the way to Hayling Island!
Contents
Prototype demo
Colin, G4EML demonstrated an early prototype in early November 2019 running on an RPi4 with USB audio dongle and a Pluto SDR enabling NB operation all bands from 70MHz to 5.6Ghz!
The protype was running a touchscreen gui written in c controlling gnu radio.
Features
- Touch screen user interface
- All mode (CW/SSB/FM/AM) narrow band transceiver
- 70MHz - 5.7GHz (the unit will actually generate a signal from 47 MHz to 6 GHz)
- Waterfall spectrum display
Here is a recent view of the receive screen
Typical Power Output
The output power was measured on NBFM. SSB outputs peak near these levels.
| Frequency | Output Power |
|---|---|
| 144 MHz | + 1.0 dBm |
| 432 MHz | + 3.5 dBm |
| 1296 MHz | +2.5 dBm |
| 2400 MHz | + 1.0 dBm |
| 3400 MHz | 0.0 dBm |
| 5760 MHz | -3.0 dBm |
Hardware
- RPi4
- Adalm Pluto
- 7" Touch screen
- USB audio dongle (see below)
- Wired USB Mouse with scroll wheel
It is proposed to use BATC Portsdown band switching and PTT control hardware - https://wiki.batc.org.uk/Portsdown2019_hardware#4-Band_Decode_Switch
Note the external filters, power amplifiers and pre-amps will be required to use the Langstone on the air - these are not considered part of the Langstone project at this time.
External rotary encoder for tuning
The tuning uses the scroll wheel and buttons on a USB mouse. You can modify this to use a panel-mounted encoder and buttons by taking a mouse apart, cutting the tracks to the scroll wheel encoder and connecting external buttons and an encoder as shown here.
USB Audio Adapter
The recommended USB Audio adapter is a cheap (under £5) adapter from eBay like this.
One working example showed up in Linux as:
pi@raspberrypi:~ $ lsusb Bus 001 Device 005: ID 1b3f:2008 Generalplus Technology Inc. pi@raspberrypi:~ $
The audio device is named in the GNU Radio Modules and alternative devices will need the code modfiying before they will work. For the receiver, it is line 74 (this may change) in Lang_RX.py:
self.audio_sink_0 = audio.sink(48000, "hw:CARD=Device,DEV=0", False)
and for the transmitter it is line 64 (this may change) in Lang_TX.py
self.audio_sink_0 = audio.sink(48000, "hw:CARD=Device,DEV=0", False)
You can find the replacement text for the receiver by running
aplay -L | grep '^hw:'
The entry "hw:CARD=Headphones,DEV=0" is for the Raspberry Pi 3.5mm audio jack output. The subsequent hw:... entry is probably what you are looking for. To get the microphone device name, run
arecord -L | grep '^hw:'
There is no default Raspberry Pi device, so there is probably only one hw:... entry.
For both the transmitter and receiver the audio device sample rate must be 48000. Devices that do not support this sample rate will not work.
Depending on the microphone being used, an amplifier may be required in front of this adapter. The SL6270C is still available (on eBay) as a cheap solution that provides ALC and filtering.
Software and code
The Langstone software along with easy to follow installation instructions is available on G4EML github.
The project is open source using GNU radio modules and all code is available on Github.
To update an existing installation to the latest version, log in using ssh, paste in these lines (without the comments):
cd/home/pi # Make sure we're in the right place Langstone/stop # Stop the Langstone killall rpidatvgui # Stop the Portsdown if it is installed rm -rf Langstone # Remove the old Langstone build git clone https://github.com/g4eml/Langstone.git # Clone the latest version of Langstone cd Langstone # Move into the new Langstone folder ./build # Build the c executable for Langstone ./run # Run Langstone
The "killall rpidatvgui" line is only required if you have the Portsdown A27 build loaded on the same system. Do remember that if you have the Portsdown loaded, there is an "Update Langstone" Menu option accessed from Menu 3.
Discussion Forum
There is a discussion forum about the Langstone hosted on the BATC Forum here: https://forum.batc.org.uk/viewforum.php?f=129
Comments and issues
Changing Pluto IP address
The Pluto comes pre-configured with the IP address 192.168.2.1. If this conflicts with your local network, this Analog Devices web page describes how to change it by editing the config.txt file on the Pluto https://wiki.analog.com/university/tools/pluto/users/customizing?rev=1575147632
The most recent Langstone code (19 May 2020 and later), copes with the changed Pluto IP address without any modification. However, if you load the Portsdown A27 system alongside the Langstone, you will need to set the revised Pluto IP address in the Langstone Configuration on the Portsdown Menu 3. This is to enable a smooth transition between Langsone and Portsdown functionality.
Inverting the Screen Image
If you have used an official Raspberry Pi Case, you may find that the Langstone screen image is inverted. To correct it, simply edit the file /boot/config.txt (using sudo):
Remove or comment out the line
lcd_rotate=2
Then save and restart.
Portsdown Integration
A special version of the Portsdown software has been developed that allows the Langstone hardware to be used as the basis for a Portsdown DATV Transceiver. Receive using a MiniTiouner is fully functional, and transmit using a LimeSDR Mini seems to work and is undergoing further testing. The special version is know as Portsdown A27 (the main road between Portsdown and Langstone) and should be loaded after the Langstone software. Instructions are here: https://github.com/BritishAmateurTelevisionClub/portsdown-a27
Here is G8GKQ's Langstone/Portsdown receiving the QO-100 DATV Beacon.
Langstone user experiences
- Dave G4FRE has used the Langstone for QSOs on 3.4GHz and received the GB3OHM beacon on 5.7GHz as shown here.
- Dave G8GKQ has received the GB3USK beacon on 23cms and is currently building a Langstone into a box....
