Saturday, January 25, 2020

EI2BED Multi-Mode Digital Gateway for the Roscommon Area



Roscommon is on the edge of the Galway DMR Network's coverage area and a reliable signal is only available on higher ground with a clear path to the Abbeyknockmoy area. Paul, EI9HQB, having an interest in DMR, wanted better access for his area and wished to encourage more operators in his area to participate. A Digital Gateway seemed to be the most economical solution. In fact, if more low cost Digital Gateways were placed on air, it would fill in the voids between the larger centres of activity.

What is a Gateway?

A Gateway is a standalone system, allowing access to the network where there is no Repeater available. A gateway is not a Repeater, but rather a device that receives a digital signal and passes it to a DMR, D-Star or C4FM network via the Internet. With DMR, Gateways generally work on a single slot basis, normally on Slot 2, which is more than adequate for general and local use.

The majority of users in Ireland use their local Repeater as a Gateway and seldom repeat in their own area. An Example: you link into Talk Group 2722 on the Gateway, this will retransmt on the majority of Repeaters in the West of Ireland and the South East provided they have Talk Group 2722 set as a Static Talk Group on their Repeater.

What does it do?
  1. Allows access and routing through DMR networks (Brandmeister in Ireland)
  2. Allows access and routing through C4FM networks such as YSF and FCS one can cross-link between YSF or FCS network into Wires-X but cannot access beyond the local Node to which the cross link is attached.
  3. Allows full use of the D-Star Network, REF, DCS, XRF and XLX reflectors
What are the advantages of running a Gateway?

For an Outlay of <300 Euro it is possible to build a Multi-Mode Gateway allowing access to the most commonly used Digital Modes. Whilst it will not act as a Repeater it will allow access into the various Digital Networks and complement the wider infrastructure of Repeaters around the Country. Setting up a VHF Gateway will give wider coverage thereby reducing the number required. The ultimate object is to gain as wide a coverage as possible. This would equate to the older network of Analog EchoLink Gateways.

A 2 metre Gateway Network set up in places such as Cork, Limerick, Kerry, Mullingar, Dublin and Dundalk would provide an excellent service and open up the use of DMR, D-Star and Yaesu's C4FM to a wider area.

Many people ask if the network in Galway is going to expand any further. The answer is a simple NO! The Galway Digital Network is covering Galway and spilling over into neighbouring counties. More than adequate for Galway's needs. Any further expansion will improve the facilities within the current system. It is down to operators in adjacent areas, with no coverage, to add to the infrastructure to benefit their own area.
Building a Gateway

Components

  1. A suitable radio such as 2 metre Tait Data Radio TM8105 Motorola GM350 to name two. VHF is more suited to Gateway operation as it will cover a wider area depending on the height of the location and antenna used.
  2. A STM32_VM Board available from Repeater Builder at this location  >>HERE
  3. Raspberry Pi 3B+ and associated Rpi Power supply
  4. Interconnecting lead with appropriate plugs 
  5. A Cooling Fan is essential to keep the radio cool during prolonged use. 
The Tait Radio will need to be programmed onto an appropriate Digital Simplex frequency. The vendor will generally perform that task if supplied with the desired frequency.
There is very little wiring and it is down to a lead connecting the radio accessory socket to the STM32 Board.

 The Tait Radio


The STM 32 board

 The Raspberry Pi 3 B+

The Software for the Raspberry Pi was downloaded from the Pi-Star site >>HERE

The file required is  Pi-Star_RPi_V3.4.17_20-Jan-2019.zip

Once downloaded unzip and etch the file onto a 16GB SD Card then insert into the Raspberry Pi.

Place the STM32 board on top of the Raspberry Pi, making sure it is seated correctly on the GPIO pins. Connect the Ethernet Connection from the Internet Router and plug in the RPi Power supply.

The Raspberry Pi and STM 32 board fitted nicely into "AVID Minidrive" case which had a low current 12V power supply and a 5A 5V power supply. Just perfect to drive the cooling fan for the Raspberry Pi. It was only necessary to run in the Ethernet cable and the connection from the Tait Radio to the Raspberry Pi. 

The Raspberry Pi will boot up and run the Pi-Star Software.

The software has to be configure with the Station parameters such as Call sign, DMR ID, frequency, Name of the controller, and the various modes in use with their appropriate servers filled in. 

A screen that appear like this is a good indication that all is connecting to the appropriate servers.
 
 .
The next task is to connect the STM32  Board to the Radio, ensure that a dummy load is connected to the radio. It is now possible to set up the audio levels on the STM32 Board from the radio to the controller and from the controller to the radio.

The setup is covered on an excellent video from >>HERE 

Further information covered >>HERE

Following a few minutes watching YouTube videos, the system was powered up and all the relevant LEDs were lighting. A DMR transmission was made on the Gateway frequencyand the pot (1) was turned clockwise until the clip LED (2) lit and then backed off until it extinguished.


This is the perfect setting for the DMR Levels. It is unnecessary to touch the Pots either side of the D connector. A call was put out on C4FM. I was daft enough to say I was seeking a signal report as I was setting up a gateway. Naturally no replys were forthcoming. Pressing the "X" button to activate the room selection resulted in an instantaneous reaction and a list of rooms appeared on the screen of the FT2D. CQ-UK was selected and a brief call was made resulting in excellent quality audio in both directions. D-Star could not be tested as the registration process was not completed but another 24 hours would see this happen.

The Radio was put into a purpose built unit with a cooling fan to prevent the radio from overheating with constant use. The Raspberry Pi and STM Board were mounted in an old Disk Drive case. which had a power supply built in to give 5v and 12v. Handy for powering the Pi and also the Cooling Fan. The Pi does tend to run hot so it was essential to keep the core temperature below 40 Degrees C.



Tuning up could have been faster if more attention was paid to the video on the Repeater Builder site. It was Rickie MI5DAW who clarified the sequence of events. It then only took 20 minutes to get the DMR peaked to perfection and 5 minuted to re-tweak C4FM and D-Star.

Some excellent QSOs were made on D-Star, DMR and C4FM.

The theoretical coverage the Multi-Mode Gateway is shown below:


The Roscommon area will be well covered by this system and this will,  indeed, encourage more to go on air. The Roscommon system will increase the Galway System's coverage.

So one week on, the EI2BED Multi-Mode Digital Gateway is working perfectly since a minor reduction of TX level on hte DMR side. Plenty of activity is noted coming through the Gateway although Paul, EI9HQB, seems to be the only operator in his area operating the system. You can lead a horse to water but ....... See a sample copy of activity from the dashboard below.


Final checks were performed on C4FM and all sounded well. D-Star was fine on installation but we had nobody to test in the Roscommon area. It was working very well on the bench so is presumed ok. All having been tested, the Gateway is now under the full control of Paul EI9HQB.

Should anyone travel to the Galway area they will find that the coverage does spill over into adjacent counties.