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)
.

Leicestershire  Repeater  Group

CONSTITUTION

(total revision 2006, amended May 2009)

  1. NAME           
    The name of the organisation shall be the Leicestershire Repeater Group, hereinafter referred to as the Group.
  1. AIMS
    The aims of the Group shall be to promote the interests of Amateur Radio and in particular to fund, design, build and maintain the electronic apparatus known as Repeaters, Beacons and such kindred devices as is deemed to be beneficial to the advancement of Amateur Radio in general.

  2. MEMBERSHIP

Membership of the Group shall be open to any individual interested in Amateur Radio.

a) Ordinary membership shall be granted to any individual upon payment of a subscription, subject to the approval of the committee. Annual renewals shall also be at the approval of the committee.  The amount of the subscription shall be decided by the committee.

Membership subscriptions shall be due annually on the 1st day of the month of the anniversary of joining the Group. If a member’s subscription is more than two months overdue his/her membership shall lapse.

b) Honorary Life membership may be granted to individuals by agreement of an AGM

c) The committee may waive an individual member’s subscription, for a set period of time, at their discretion 

d) A reduction of 25% in the current rate of subscription for membership is available to qualifying individuals on application.

Family Membership – Each immediate family member after the first paying member will qualify for the reduction.
Full time students, Disabled persons, registered unemployed and individuals of State pensionable age also qualify for membership subscription reduction.                      
Special Note  Individuals can qualify for one reduction in subscription only. Other concessions are at the discretion of the Group Committee, which is the final arbiter in all matters of qualification.

e) All members shall abide by the constitution of the Group. The committee shall have the power to expel any member whose conduct, in the opinion of the majority of the full committee, renders that person unfit to be a member of the Group, or who brings the Group into disrepute. No member shall be expelled without first having been given an opportunity to appear before the committee.

  1. AFFILIATIONS
    The Group shall be affiliated to the Radio Society of Great Britain, said society being authorised to act on its behalf in negotiations with OFCOM
  1. COMMITTEE
    The day to day running of the Group shall be carried out by a committee, which is elected and managed according to the following rules:

5.1 A committee consisting of the following members shall be elected at each AGM

a) Chairman

b) Secretary

c) Treasurer

d) Engineering Manager  

e) Site Manager

f)   Three ordinary members  

No member may be elected to continuously hold the same position as officer for more than 3 years in succession. That member may be elected to the same position after a break of one year. Officer means Chairman, Secretary, Treasurer, Engineering Manager and Site Manager. In the event that no volunteer comes forward to fill any of these posts, then the existing post-holder, if willing, may stand for another year subject to the usual electoral process

5.2 An elected committee shall have the power to co-opt members for any purpose. Such members shall have full voting rights if approved by the committee.

5.3 Committee meetings shall be held monthly.  All committee members shall be given 7 days notice of such meetings wherever possible. The quorum for the committee shall be 5. In the absence of a quorum business can be dealt with but any decisions taken only become valid after ratification at the next committee meeting at which a quorum exists. Where necessary the Chairman of the meeting shall have a second and casting vote.

  1. MINUTES OF MEETINGS

    6.1 Minutes of all General and Committee meetings shall be taken and produced within 21 days of the meeting. A copy of any such minutes, once approved by the committee, shall be supplied promptly, and in a typed form, to any member upon request provided that the request is accompanied by a stamped addressed envelope. Requests for minutes shall be sent to the Secretary. 

    6.2 In the event that it has been impossible to elect or co-opt a secretary for whatsoever reason then section 6.1 above shall not apply.
  1. EXPENDITURE

    7.1 All expenditure shall be at the discretion of the committee

    7.2 When making purchases for whatever reason, efforts should be made to secure the lowest prices and receipts for goods and services should be retained.

    7.3 Any committee member with a vested interest in any payment put before the committee shall declare his/her interest and shall take no further part in the approval process. Any committee member with such a vested interest in a payment may not be a signatory to any cheque, drawn on the groups account, relating to such a payment
  1. ACCOUNTS 

    An approved set of accounts shall be given out to members at the AGM.  All monies received by the Group shall be promptly deposited in the Group’s bank account. The bank accounts shall be maintained in the name of the Group and two authorised officials shall sign all withdrawals and payment instructions, one of whom will normally be the Treasurer. 
  1. LEGAL ADVICE

    Legal advice shall be taken with regard to the insurance of and of the law applicable to the Group as and when required.

  2. EXTRAORDINARY GENERAL MEETINGS

10.1 An EGM may be called by the committee, or any 10 members.

Said meeting shall be arranged for a date within 28 days of the request being received by the committee.

10.2 Notice of any EGM shall be sent to all members by 1st class mail, or electronically, at least 14 days in advance of the meeting. Such notice shall contain the following:

a) Date and venue of the meeting.

b) Method and if not called solely by the committee, names and callsigns of members who have called the meeting.

c) Reason(s) for which the meeting has been called.

d) A brief agenda for the meeting.

e) No other business may be transacted at the EGM

  1. CONSTITUTION

    The constitution may only be amended by agreement of a General Meeting. Notice for said meeting shall be 28 days given to all paid up members. Said notice to state amendment(s) being proposed. Provision shall be made for postal voting. Scrutineer(s) shall be appointed by a vote of the members attending to count the votes cast and to decide on the admissibility of any postal votes. The scrutineer(s) decision(s) shall be final and binding.
  1. ANNUAL GENERAL MEETING

    An AGM shall be held each year in the month of May. All members shall be given 28 days notice of said meeting by post or electronically. Postal voting is not allowed except for matters relating to amendments to the constitution. Proxy voting is not allowed.   

  2. EQUIPMENT

    The Chairman, in conjunction with the Engineering Manager and the NoV holders shall maintain a list of all MAJOR equipment. Said list shall be updated whenever the status of a piece of equipment changes. Each entry shall relate to a specific item or group of items and shall contain the following detail:


13.1

a) Date of entry.
b) Brief description of item.
c) Comment/reason for entry i.e. acquired, sold, discovered by way of inventory, change of location
d) Make, Model and serial number where appropriate                                  
e) Location where item is held
f) Signature of person making entry

13.2 Said list shall be made available for inspection by members at any General Meeting.

13.3 In order that the equipment list be kept up to date an inventory of equipment shall be carried out at least every six months.

13.4 Generally, all equipment in use by the Group shall be the property of the Group, either purchased or donated . Items on short or long term loan, the property of individual members, or others, shall be accurately minuted and a written and signed statement as to ownership shall be maintained by the Secretary. All such statements to be signed by the Secretary and the beneficial owner and a copy shall be held by all parties involved.

14. WINDING UP OF THE GROUP


14.1 The decision to wind up the Group may only be taken at an EGM called specifically for that purpose, and that purpose only.   

14.2 The winding up decision may only be ratified by a simple majority of the members attending that final EGM. Postal and proxy voting is not allowed. 

14.3 The funds and assets of the Group shall, after discharge of all liabilities, be disposed of as directed at that final EGM to a society or charity with similar interests.

  1. GENERAL MEETINGS

At all types of properly convened General Meetings decisions shall be by a simple majority of the members attending. At all such meetings the Chairman of that meeting shall have a second and casting vote.

15.1 Only fully paid up members, having been members of the group for a minimum of three months may attend and vote at General Meetings.   

 

Abbreviations used in this document
 The Group:     Leicestershire Repeater Group
 AGM:             Annual General Meeting
 EGM:      Extraordinary General Meeting   
 Member:     Ordinary, Life or Committee

Total revision: May 2006, amended May 2009.

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

 

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