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!

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:~ $

Other adapters may 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....