If there's one thing missing in Devon and Cornwall, it's a Ham DMR repeater.
OK so it may not look quite like this but we have decided to go for a more subtle "camoflaged" approach.
.... is it G6BJJ's Bongo or NASA mission control?
But rather like this ================>
meet our new repeater keeper and guardian!
West Devon Raynet is joining with Cornwall Raynet to set up and provide Devon & Cornwalls first active dedicated amateur radio DMR repeater, to join the ever growing network of DMR repeaters around the UK and the world.
Full details of the project and the actual location are not being published in full yet, other than to say it will be on Dartmoor (somewhere) and is hoped to cover the West Devon and East Cornwall area.
Our biggest problem, apart from getting "Mint Sauce" the sheep to stand still whilst we all use the thing... is nailing & glueing all the bits together and weather proofing them to keep the Dartmoor summer blizzards and monsoons at bay.
GB7RD is now licenced and will be starting the first tests this next week. Initially it will be working in a "Stand-alone" mode for the tests.
Details for GB7RD are
TS1 (local) TG9 Colour Code 3, Rx 439.6875 Tx 430.6875
TS2 (link) TG's not yet activated whilst on initial tests but will again become Colour Code 3, Rx 439.6875 Tx 430.6875
GB7RD has now joined and is part of the Devon & Cornwall Repeater Group.
Watch this space for more information.
The new DMR System...
Radioddity GD-77 Hytera MD785 Mobile Tyt md-9600 Retevis RT3/TYT MD380
Dual Band Handheld Dual-band Mobile
DMR (Digital mobile Radio) is actually nothing new and has been around for some time. It is however new to the amateur radio world. Originally sold as a commercial system by Motorola under the brand MotoTRBO it is a highly effective system with a long pedigree and good track record not just for voice but also data.
Interest in all things digital in the radio world has been spurred on by the interest and growth of Icom's D-Star and Yaesu's C4FM Fusion systems. However for many the extremely high cost, (£400+ for a handheld, £500+ for a mobile) even when imported direct, cannot be justified. This is where the DMR sets come into their own for around 1/3 of the price.
However they do work in rather different ways to the other main amateur radio systems, and this is where some confusion can set in... like anything new it can be a steep learning curve until you get the hang of it. Icom & Yaesu's systems are mainly a case of programming in your amateur callsign and the mode FM or a digital one (Auto C4FM, Narrow Digital [for voice and data], Wide digital [for voice only], D-Star etc. You also have the ability to input a frequency either in memory or to use a direct entry VFO. DMR is different - it has no VFO, all information for each frequency/mode must be entered into a channel memory - then cross-linked with a common setup Zone. Each callsign must have a Radio ID which must be obtained from a central international registry. Like D-Star & Fusion, you can direct your call through a repeater network that is linked around the world to a specific location, or call set to set. The way this is done however is different with DMR in that it must be contained within the memory for each frequency, repeater or link. Again like other digital systems, voice transmissions are broken up into data packets of a fixed time duration and interleaved with header information to route the call to the appropriate destination. With DMR however, this is done by using TDMA.
Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.[DMR uses 2 slots] The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same frequency channel while using only a part of the channel capacity. C4FM uses FDMA [Frequency-Division Multiple access]. see below. Each have their own advantages and drawbacks.
So which is best?
Thats a bit like asking which is better red wine or white wine. The answer is simply, its up to you.
Some people prefer red wine, some prefer white, some don't like either. In the case of Digital Radio a lot will depend on the depth of your pocket, the tolerance of your other half, your personal preference or what others are doing in your area. But for many it may well come down to cost. Can you justify spending ~£1000 for a mobile and handheld from the big 3 manufacturers (I, K & Y) or £300 - £400 for a DMR setup? (remember the days of VHS vs Betamax? Betamax was probably the better system but could not compete with the lower prices of VHS)
At the annual Tavistock Goose Fair which is held on the second Wednesday in October each year, we act as the link for the Police, South West Ambulance, St John Ambulance, Tavistock Town Council, West Devon Borough Council, the Bus services and the Park & Ride Scheme.... as well as a general information and lost property, children and granny point!!!!
Here the "ISU", "battle-beast" or "Thunderbird 5" as it is variously known, is setup and running in the centre of Tavistock beside the Ambulance and First Aid points.
Each year, we run from around 05:00 to 01:00!!!
Due to COVID-19 2020 is cancilled
...quick more coffee!!!
|Switch & Circuit||Function||Circuit||Wire Colors||Use|
|Connector Block 1 – (new block)|
|Switch cct 1||Locking||1||Light Green||Amber Strobes|
|Switch cct 1||Locking||1||White||Amber Strobes|
|Switch cct 2||Locking||2||Blue||Amber & Red Strobes|
|Switch cct 2||Locking||2||Green/Yellow||Amber & Red Strobes|
|Switch cct 3||Momentary||3||Green||Not used|
|Switch cct 3||Momentary||3||Orange/Black||Not used|
|Rocker switch 4||Locking||4||Orange||Locking PTT|
|Rocker switch 4||Locking||4||Black/Blue||Locking PTT|
|Push Switch 5||Locking||5||Pink/Black||Radio Power on/off via relay|
|Push Switch 5||Locking||5||Red/Yellow||Radio Power on/off via relay|
|Connector Block 2 - (same as original)|
|Engine Stop cct 6||Variable||6||Sep. Plug|
|Headlight Hi/lo 7 & 8||Adjustable||
|Engine Start||Push||9||Separate plug|
Fitting the new switch pod on the ST1100 is straightforward.
The Police Switch pod comes with 2 connector blocks (Red & Green). The smaller (Red) is the same as the original connector for the standard unit and plugs straight in. This is for the Engine start, kill switch and headlight hi/lo switch.
The extra block (green) is the connector for the P Spec ST1100, this needs to be adapted for a standard Pan.
The new pod has 10 wires (9 in a bundle into the new block, plus 1 free) and the colours are as shown. Unless you have the correct 10 way block already on your ST1100, it is easiest to cut the wires out of the block as close to the block as possible.
The maximum current rating for each of these cables is 5 amps. If you intend to connect anything which draws close to or more than 5 amps you will need to go via a standard relay.
I used a 7 core cable to run from the front to the rear pannier which housed all the extra battery and strobe gear, plus a 2 core PTT line to locking and momentary PTT switches in parallel. You could combine this and use a 9 core cable, but getting a cable rated at 5 amps is not easy and costs a small fortune. Also the cable diameter gets rather large.
To Fit the Pod:
Note you will need new fitting bolts to hold the unit as the old ones will be too short.
- Remove the brake lever to give easier access.
- Loosen the brake master cylinder/fluid reservoir and slide it as far inboard as possible. The new pod is ~ 5 – 8mm wider than the original.
- Remove the retaining bolts and remove the old switch unit. Careful to not dislodge the throttle cables.
- Remove the old engine/headlight connector (Red?) making sure not to damage the sockets.
- Plug in the new engine/headlight connector (Red?) making sure not to damage the sockets. Wrap in waterproof/self amalg tape.
- Loosely fit the new switch pod onto the handle bar taking care not to trap the throttle cables or engine control wires.
- Adjust the position to allow correct operation of the throttle. Bolt down unit, again making sure free movement of throttle.
- Slide the brake unit back against the new switch pod and tighten locking nuts.
- Refit brake lever.
- Check for full and free movement.
Wiring the new Switch Pod:
You will need a 12v auto relay for the radio plus further relays for any kit drawing more than 5 amps.
- Run the 7 core cable to the rear o/s pannier.
- Run PTT cable to Radio as normal
- Identify each of the 10 wires from the new switch pod and arrange them in pairs.
- Connect pair 1 (light green) to amber strobe controller + and (white) to battery +
- Connect pair 2 (blue) to red strobe controller + and (green/orange) to battery +
- Isolate pair 3 (dark green & orange/black)
- Connect pair 4 (orange & Blue/black) to PTT line in parallel to push PTT switch on left handle bar and to Radio.
- Connect pair 5 (red/yellow) to 12v relay coil input (pin 86), connect (pink/black) to battery +, connect relay output (pin 85) to earth.
- Connect relay power input (pin 30) to battery.
- Connect relay power output (pin 87) (n/o) to radio.
4 Pin 12v Relay Pin 30 is 12v live, 85 & 85 Relay coil, 87 ground.
5 Pin 12v Relay has an extra contact 87a. This pin is normally closed (& live) when the coil is un-powered.
Since the FTM-100 is always drawing power even when switched “off” and for safety, I have added an in-line power switch. This actually comes via a relay from the right handlebar switch remembering that the power the rig draws can be significant (High power Tx on 70cm ~13amps+)
The connections to the PTT, Mic and speakers all run via the Microphone and speaker sockets on the main body of the FTM-100. (You could use the DATA port if you prefer.) To keep things simple, I took a spare microphone for the FTM-100 (the MH 48) and removed the Mic capsule and PTT switch from the circuit board, leaving the rest of the unit in the case. The reason for this is that the FTM-100 uses a powered non-standard electret mic element (needs to be exactly 1.2KΩ)
The wires run away as follows:-
PTT+ and PTT- to a non-latching switch on the left handlebar and in parallel to a locking switch on right handlebar switch pod.
Mic+ and ground via the interface box (the old mic unit) and
Speaker+ and ground via the speaker socket to the helmet.
A second speaker line has been run to a waterproof loudspeaker on the bikes dash from the speaker socket, but I have added a switch so I can silence it if required.
The speaker and microphone built into my helmet has a safety break away connector, to allow disconnection getting off the bike, but more importantly to come away if I unexpectedly part company with the bike whilst riding it! This is done with a waterproof 6pin DIN plug and socket (plug = helmet end) although it is possible to use a ¼” stereo jack and line socket, which I previously used for many years on my old Honda Silverwing. The important thing is the socket should be waterproof to prevent corrosion.
Mounting the antenna…
It’s worth mentioning the antenna setup for a second, after all this is really the business end of the radio. A poor antenna mounting is worse than useless and could damage the rig.
Whatever type of antenna you use, it must be strong, and mounted to a good earth. When fitted on a car, there is a massive ground plane under the antenna. You don’t have this on a bike so I found the best way was to fabricate a flat metal bar at least 3mm thick and ~60mm wide. The bar should be long enough to pass completely under any top box and leave enough room on the Off-side to fit the antenna mount. This stops the antenna bouncing on the top-box and prevents an annoying sound at best, or a damaged top box and antenna at worst.
The flat bar is firmly bolted to the bikes frame using the top box mounting bolts. I drilled two holes the same diameter as the top box bolts and fixed the bar between the bolts and the top box mounting frame to ensure a good earth. As my top box frame is metal it also acts as a radial to improve the earth. The rig is dual band so I have gone for a solidly built dual band antenna, the Comet SBB2 (63cm long 2.5db/5db) is ideal for general round town work and the SBB4 (96cm long 3.0db/5.5db) for Raynet work/longer runs.
That's it. It works and I have had quite a few interesting chats with various other radio hams, not just locally but via the repeater networks literally all over the world and it always raises an eyebrow when you sign as “/motorcycle-mobile!”