GB3CF GB3LE GB3UM GB3GV GB3LES GB3LEX GB3LEF GB3LEU

 

The Leicestershire Repeater Group was formed in April 1975 with the aim of promoting the interests of amateur radio, and in particular to design, build and maintain electronic apparatus known as repeaters, and kindred equipment.

A Repeater is a relay system primarily for mobile and portable radio users. Such as from the car or on foot. Located high up in Charnwood Forest, Leicestershire, our systems extend your range by many miles and beyond the county.

We do this by re-broadcasting your VHF, UHF, microwave or TV signals.

The complex radio beacons and switching equipment are maintained by members and helpers

We welcome membership and donations from anybody who has an interest in our operations, please click here for more information regarding membership or you can make a donation by clicking on the Donate button *Please do not use this button to pay your membership*


We recommend that all users of our repeaters read the RSGB information regarding repeater abuse, this includes links to the OFCOM information sheet which is available here


We currently operate four repeaters and four beacons, more information on each repeater and beacon (including status) is available by clicking on the ☰ icon at the top left hand corner of this window.

Mobile and Tablet users will find the main navigation menu on the top right of their screen identified by the ☰ icon

 

For many years, reading of the GB2RS news at 09:00 every Sunday morning has alternated between Mike G0ATR and Geoff G4AFJ. Since the sad passing of Geoff, Mike has come to the difficult decision that he cannot continue to read the news every week.

If there is anybody else who would be prepared to assist Mike by sharing the news reading duties, please get in touch.

Until another newsreader is found, there will unfortunately be no news on GB3CF.

By Phil Taylor M0VSE

In 2016, it was agreed by the Leicestershire Repeater Group committee to implement the Yaesu Fusion C4FM mode on GB3CF and a Yaesu DR-1X repeater was purchased for this purpose. It soon became apparent that the DR-1X was severely limited and it was decided that the analogue features on the repeater were not suitable and apart from a couple of on-air testing sessions, the plan was shelved.

In early 2018, I started investigating other options and discovered the MMDVM (Multi-Mode Digital Voice Modem). MMDVM is the brainchild of Jonathan G4KLX to develop a small hardware device that was capable of supporting multiple digital voice modes, originally the GMSK (D-Star only) and realised using Arduino boards together with a 'hat' that provides audio amplification and filtering, it has developed into a whole host of hardware devices using STMicroelectronics STM32 ARM CPUs allowing for more complex modes to be supported.

There are now a large number of MMDVM hardware devices available, mostly based on a reference design by Andy CA6JAU with many modifications and improvements by a dedicated band of hardware engineers. The range also includes a number of "hotspot" designs that incorporate an Analog Devices ADF7021 RF transceiver chip. Some have the same form-factor as a Raspberry Pi Zero meaning that a fully-functional multi-mode hotspot can be created in a device smaller than a pack of cigarettes (whatever that is!)

The MMDVM is a true 'modem' in that its sole purpose is to modulate and de-modulate digital signals. It is able to do this in real-time due to the monolithic nature of the MMDVM firmware as it doesn't have to concern itself with other processes (networking, connection management etc.) These functions are provided by some software called MMDVMHost which is typically run on a Raspberry Pi but as the MMDVM device itself emulates a traditional RS-232 serial port, it can run on practically any computer that is capable of running the Linux operating system.

Each supported mode (DMR, D-Star, C4FM, NXDN or P25) also has "gateway" software available which talks to MMDVM and provides network connectivity to the various reflector networks. It has been designed in such a way that the gateways can either run on the same computer as MMDVMHost or for larger more-complex systems, each can be run on their own dedicated computer. This design means that the MMDVM 'infra-structure' is incredibly flexible and scaleable for larger multi-repeater implementations.

Although not being used on GB3CF, it would be remiss to not mention Pi-Star as this is the software that many users of MMDVM devices will be using. Prior to Pi-Star being created by Andy MW0MWZ in August 2014, creating a hotspot or repeater using the GMSK required significant knowledge of the Linux operating system. In the early days, this was based around the G4KLX DStarRepeater and ircDDBGateway suite but when Jonathan conceived the MMDVM concept in 2015, it was adapted to support the additional modes supported by the MMDVM. It is basically a single disk image comprising of Raspbian Linux, MMDVMHost and all available gateways, together with web-based configuration and dashboards. This has led to the large number of MMDVM based hotspots now appearing as no real knowledge of Linux or MMDVM is required to get up-and-running.

With GB3CF, I had a number of specific goals that made it more practical to build the operating system from a "clean" Rapbian image and manually add all required software. Specifically the need to also support analogue FM which is not currently supported by MMDVM.

As the Raspberry Pi is designed to boot and run from a Micro SD card, I wanted a method of reducing how much writing was done to the SD card on a regular basis, so I developed everything to run in RAM as much as possible (including logging and process id files etc.) and the default setting is for the system to run in read-only mode, only switching to read-write if configuration changes or upgrades are required.

Another major feature was the ability to support analogue FM and to be able to auto-switch between analogue and digital modes. After a lot of research, I discovered the MMI interface from Thomas DO7TPB and Peter DK4HPA which was created for exactly this purpose. It is basically a "Pi Hat" which attaches to a Raspberry-Pi and provides audio switching between an integrated USB sound card and MMDVM board using a TI 4066n analogue switch IC. This, combined with Svxlink repeater software can create a system capable of repeating both analogue and digital voice. Incoming (receive) audio is fed to both the MMDVM and USB sound card simultaneously and if a valid analogue (or digital) transmission is detected by either Svxlink (CTCSS squelch) or MMDVM (valid digital transmission). If either Svxlink or MMDVM enables their PTT connection (to transmit) then transmit audio is connected by the MMI board to the transmitter audio input. Once PTT is turned-off, audio output is disconnected.

Thomas and Peter had created a number of scripts that monitored the status of MMDVM and Svxlink and disabled one while the other was transmitting, but I decided to do this a different way and developed modifications to MMDVMHost itself. My changes allow it to communicate with Svxlink via TCP connection and to inhibit transmission on one mode while the other is transmitting. This also has a configurable hang-time (default 30 seconds) which will keep the repeater locked to the last transmitted mode until the timer has elapsed. My modifications are available at https://github.com/m0vse/MMDVMHost/tree/svxlink although significant changes are likely to be needed for them to work in a different environment.

As mentioned, the analogue repeater is Svxlink by Tobias SM0SVX. This is an advanced analogue repeater controller with a whole host of features. On GB3CF, many of the advanced features are currently disabled but the ability to enable Echolink, Parrot, VoiceMail etc. is available if required in the future. Many aspects of the repeater can be customised by modifying .tcl scripts which is what I did to achieve communications with MMDVMHost. This means that no modifications to the core of Svxlink were required.

Although the repeater site has Internet access, I have also included a real-time-clock module which is something that the Pi doesn't have as standard (meaning that at power-on the clock always starts from 2016!), this ensures correct time even if the Internet is down. The repeater also synchronises using NTP (network time protocol) with the time UK time server pool located at uk.pool.ntp.org.

I also wanted to provide a (near real-time) dashboard that allowed members of the LRG to see activity on the repeater. Having evaluated various dashboards, the problem was that they all relied on parsing MMDVMHost log files 'on the fly' which I thought was pretty in-efficient and I wanted to be able to hand-off the dashboard feature to a remote web server and database that was better suited to handling web traffic. I discovered mmdvmdash by DO6UK which used a novel idea in that it constantly 'tailed' the log files and parsed each line as it was created. Any accesses then get logged into a local SQLite database and it could optionally synchronise this with a remote MySql database. Unfortunately it only supported DMR (the one mode that we are not licensed for!) so it required significant modification to get to the dashboard that we now have. I practially re-wrote the whole thing in the end (learning Python into the bargain) and made it multi-threaded.


Hardware used on GB3CF

  • Tait TB7100 VHF repeater
  • Raspberry Pi 3 Model B+ (1.4Ghz quad-core CPU with 1GB RAM)
  • MMDVM-PI from Jim KI6ZUM (creator of the Zumspot hotspot)
  • MMI Rev.B interface from Thomas DO7TPB and Peter DK4HPA
  • I2C based real-time-clock module from PiHut

Software used on GB3CF

  • Raspbian Linux for Raspberry Pi (Currently "Stretch" release)
  • MMDVMHost (with modifications by M0VSE)
  • Svxlink (analogue repeater)
  • ircDDBGateway (gateway to the IRC D-Star network)
  • YSFGateway (gateway to the YSF System Fusion network)
  • NXDNGateway (gateway to the burgeoning NXDN network) 
  • mmdvm_parser and remote dashboard

In May 2018, after successful tests of multi-mode running on GB3CF, it was decided to investigate running GB3LE in digital mode as well. Leicestershire Repeater Group had previously purchased a Yaesu DR-1X repeater in 2016.

It was intended that this repeater would be used on GB3CF, but the lack of control over analogue operation (mainly the inability to produce a confidence tone or "K") meant that it was 'shelved'.

As the intention was for "LE" to operate mainly in Yaesu System Fusion mode, the lack of a "K" was not thought to be too much of a problem, so at the end of May, the replacement repeater was installed. It currently consists of the following new hardware (in addition to existing cavities etc.):

  • Yaesu DR-1X repeater
  • Yaesu HRI-200 Wires-X controller
  • LattePanda miniature computer 

The repeater is configured with the latest firmware and software versions currently available from Yaesu and has full connectivity to the Wires-X network. Initial reports are very good with reported coverage being similar to the old LE.

We are in the process of creating a "dashboard" on the LRG website which will show repeater activity in much the same way as the existing GB3CF dashboard (membership required).

If you have heard interference or abuse to any of the Leicestershire Repeater Group repeaters, we would like to hear from you. Please provide as much information as possible in the form below

This information will be collated and will hopefully allow us to determine a pattern of abuse.

All information will be kept strictly confidential but numbers and types of interference may be shared with OFCOM and/or RSGB to assist their investigations.

Your Name*
Your callsign (or none)
E-mail address:*
Your location:
Date of interference:
Approx time:
Which repeater?*
Is interference audible on the repeater input?
Select the type of interference:*
Any more information?
Please provide as much detail as possible including bearing to interference (where known)
.

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