ThunderStruck Progress.

Pajero Jan 2016

Pajero Tracking Vehicle Update

We are on the move after several delays. The proof is in the progress since our last post. We are now talking boosters from our balloon platform to get us to space and we are working on our technology. Balloon test flights are being planned for late January / early February

So lets look at what my son, Jason (13), and I have done and are doing about the tracking vehicle. We will have more, but we are planning on at least having our 4WD SUV ready for the trans-sonic test as soon as we get this approved by CASA – the Australian Civil Aviation Safety Authority.

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Equipping our Tracking Vehicle

Pajero Centre ConsoleTracking Equipment and Mobile Technology

One of our big issues when working with balloons and supersonic gliders is that they never stay still. Even our balloon flights have reached an astonishing 230kph over land by simply climbing through the jet stream. Basically, the car can’t keep up. Even if we could travel at such mind-blowing speeds, we could never follow the same path and have to stick to roads that crisscross the landscape and never in an easy route across country. Mind you a recent flight did travel straight along the Mid Western Highway and have the courtesy to land within a few hundred metres of the main road in sheep grazing paddock. – no crops and no trees.

Simply we need to have not just good tracking, but great tracking. That is where the car needs to be able to cater for several technologies and that means radio and wireless data connections. Our car has just this capability and we need more. We have chosen a Pajero 4WD as we will need some rugged ability for off road work. In the past we have had to drive right through a 200m bit of forest without any road or fields that may have had animal burrows. over logs, through streams and much, much more. The Mitsubishi Pajero Escape is an older model, but still good and we have used it for balloon flight tracking in the past.

In Australia, the most common tracking for High Altitude Balloons (HAB) is via either HAM radio APRS for non commercial activities and RTTY on UHF for commercial activities.

Our Kenwood D710 radio sits on the central part of our dashboard in the car - easily able to display where we have to head.

Our Kenwood D710 radio sits on the central part of our dashboard in the car – easily able to display where we have to head.

Ham Radio APRS

APRS stands for Automatic Packet Reporting System and is a digital communications information channel that is capable of handling information such as GPS (Global Positioning System) data. This is ideal for tracking balloons. Ham radio hobbyists simply build receivers and port the data to a central server. Several receivers may pick up the signal and port the data which i recorded in the database. In our case every 20 seconds. The frequency of the reporting interval is important as the payload gets near the ground so that the radio can easily be located. In some areas there are no receivers and internet connections  – known as iGates. Care needs to be taken, but the solution is to have a mobile iGate in the car if there is good mobile wireless coverage in the area. We are preparing to have a mobile iGate in the tracking vehicle. Until then we have a high power APRS repeater. It receives the data and resends it to an iGate that is in range. Occasionally this is in another of our tracking vehicles and the ability to relay is important.  If you want the full details, you need Internet connectivity in your vehicle, either through a tablet or PC.

UHF RTTY

In Australia, it is illegal to use APRS to track commercial flights. We have to use something like the globally accepted UHF RTTY system. RTTY in Australia can be on multiple channels on 434MHz. and can only be 10mW of power. This is fine if you have height and can track to the ground. As with APRS, you need to be nearby when the unit is near the ground or the curve of the earth will cause the signal to be lost possibly 1Km above the ground. on a windy day this can lead to a big search area. Similar to APRS, there are many people that place a UHF RTTY gateway in their vehicle and gate the data to an internet server. If you want the full details from the server, you need Internet connectivity in your vehicle, either through a tablet or PC.

What is Installed in the Vehicle So Far?

Let’s do a list of the basics:

  • A Kenwood D710 APRS capable transceiver (VHF/UHF) with tracking display and GPS integration
  • An Icom IC-7000 all band HF/VHF/UHF transceiver that is RTTY capable (but does not display tracking)
  • An 80 channel CB radio on UHF (in case we have a non ham radio car in the group
  • A Byonics MT-400 10W APRS Beacon
  • A wireless mobile modem with a wired and WiFi router (so to have an external antenna) runs of 12 volts
  • A motorised antenna raiser – the big antenna hides in front of the roof rack and is near invisible.
  • A multi-socket cigarette lighter system for power for many items

What we need to be installed

Let’s do a list of the basics:

  • HF radio antenna (we have the Icom -700 HF radio side hooked into a 100w termination for safety)
  • An auto-tune system for the HF radio
  • Another big VHF/UHF  antenna with a motorised lifter.
  • 2 x 900MHz antennas
  • A 900Mhz antenna for 56Kb modem access to the balloon and ThunderStruck systems
  • Radio Controller as used for flying model aircraft
  • A video downlink on a band to be decided.
  • A visor and screen display for the video from the balloon payload and ThunderStruck aircraft.

So we are already halfway there, but still have a long way to go and need your help with funding. More on that soon. It is clear that we have a lot of this gear tested and bedded down and that is a good thing. Part of my requirements with this vehicle is to make it inconspicuous. Being old is a start. Hiding all the antennas is another. One antenna is super thin and near invisible, another is very short and the last folds down in line with the roof rack. The photos below show the antenna folded down and raised.

Antenna folded down

Antenna folded down

Antenna being raised

Antenna being raised

Antenna fully raised

Antenna fully raised

The fully raised antenna

The fully raised antenna

The antenna can be raised when driving and it lets us enter car parks without a second thought. We have a switch on the centre console, but i am thinking of adding a proximity alarm in case we forget that it is up. That is the switch to the right of the cigarette lighter. Sorry for the debris under the switch. We had just finished installing the Icom IC-7000 above it.

Centre console antenna switch

Centre console antenna switch

The passenger's side of the centre console with the CB radio and the 3 socket cigarette lighter extension unit

The passenger’s side of the centre console with the CB radio and the 3 socket cigarette lighter extension unit

The 10W APRS unit with the GPS receiver to the left of the transmitter

APRS 10W tracker with the GPS receiver to the left of the transmitter

In the picture above, we could have mounted the unit under the dashboard, but it is a little more versatile being  accessible. I also took the opportunity to hard wire the GPS Navigation unit directly to the car wiring. Since the 12 volt plug has the 5V system, we ensured that the charge unit from the plug was in circuit.

The IC-7000 in RTTY mode

The IC-7000 in RTTY mode

Note that I did not change the frequency to 434.650MHz or similar frequency where RTTY resides. I just wanted to show the fact that it does RTTY. The output at the back of the radio connects to an interface box and can then connect to your PC.

Pajero Centre Console with the Kenwood D710 on the top and the IC-7000 at the bottom of the console.

Pajero Centre Console with the Kenwood D710 on the top and the IC-7000 at the bottom of the console.

Note that the IC-7000 display is only a front screen. There is a cable to the base unit under the driver’s seat. it is wired so that the microphone and front screen can be moved to the rear seat so that an operator in the rear of the car can operate the unit. Similarly the base unit for the Kenwood is also under the drivers seat.

Kenwood D710 display  on the centre of the dashboard

Kenwood D710 display on the centre of the dashboard

Note that the unit above has its GPS hard wired. Like the IC-7000, it is a dual VFO. Only the B VFO is displayed above, but you can operate the VFOs on different bands or channels. It is very versatile.

Our Kenwood D710 radio sits on the central part of our dashboard in the car - easily able to display where we have to head.

Our Kenwood D710 radio sits on the central part of our dashboard in the car – easily able to display where we have to head.

The image above is displaying the rough compass direction to the station displayed. It shows an actual bearing (325 degrees) to the target and there is also a distance in 100m increments. Since the beacon was very close, it shows 0.0Km. A second display shows position altitude and speed.

Mobile Wireless modem, router and WiFi hotspot.

Mobile Wireless modem, router and WiFi hotspot.

Finally the above shows our mobile hotspot unit. It still needs its external antenna for really good mobile coverage, so it is temporary. It uses the rear 12 volt outlet next to the torch (bottom left) for power and once the antenna is installed, the modem will not be on the cable, but plugged directly into the TP-Link unit. We also have 4 hard wired network connections for future units such as the mobile iGate.

Also note that there are two other trackers on board that I will not disclose. It has significant anti-theft devices and tracking, so don’t come after this car. it might just get you caught.

Anyway, we are halfway there for Project ThunderStruck. We are extremely ready for any High Altitude Balloon flight.

Technology Taking Shape – Radio Links

Control SystemFinalising ThunderStruck’s Radio Links

Aside from the airframe and servos, one of the hardest planning jobs is designing and building the various radio links.

It is pretty simple. Radio links are essential and not just nice. They will be mission critical to the success of the project, but we will have backups to complete the flight without crashing, etc. The links must be solid and with no breakup and must operate over long distances.

It is very important to realise the differences with the ground based systems and the aircraft systems. With the ground based systems we can have high power, large antennas, antenna tracking, mains/generator power and much more. on the aircraft we have both power and space issues. We also have temperature issues and the equipment must be tested in chambers that have had the air pumped out – I don’t like to use the term “vacuum”, but it is descriptive for most people.

How many links will we need?

At the moment we will need 4 radio links – 2 for the balloon and 2 for the aircraft.

  • The balloon telemetry system
  • The balloon camera system
  • The aircraft telemetry system
  • The aircraft camera system

We want to keep the video links separate from the telemetry as delays in the telemetry information can cause major issues. If you have ever had a large file download interrupt a Skype call?  you will know exactly what I mean. Imagine flying a supersonic aircraft and having dropouts on the links to the flight system! We can’t have that so we separate the systems. We also need to separate the balloon and aircraft systems as we will need to maintain video from the balloon well after the aircraft has separated from the balloon. We will also need to command the balloon to terminate its flight after separation. The most critical link of the 4 is the aircraft telemetry system and we have chosen a 900MHz 1 watt system. It is pretty amazing and handles 56Kb per second both ways at a distance of 80Km with diversity. Diversity is super important. I have posted the specifications on and earlier post, but I will repost them below. It can link directly to our control system and also to a navigation system such as the Pixhawk that we have chosen. The simple set up can be seen in the following diagram. More on this and the other links in a later post.

Control System

Note that in the above radio link system, the yagi antennas may have auto-tracking and will probably be vertical and horizontal diversity. We are toying with the idea of circular polarisation. More on patch antennas later.

From the RFDesign Website:

RFDesign is an electronics design and manufacturing company specialising in Embedded systems, Radios, Antennas and high frequency electronics. We are located in Brisbane, Australia with our office located in Acacia Ridge, QLD. 

Features:

  • Long range >40km depending on antennas and GCS setup
  • 2 x RP-SMA RF connectors, diversity switched.
  • 1 Watt (+30dBm) transmit power.
  • Transmit low pass filter.
  • > 20dB Low noise amplifier.
  • RX SAW filter.
  • Passive front end band pass filter.
  • Open source firmware SiK (V1.x) / tools, field upgradeable, easy to configure.
  • Multipoint software capability with MP SiK (V2.x)
  • Small, light weight.
  • Compatible with 3DR / Hope-RF radio modules.
  • License free use in Australia, Canada, USA, NZ

 Interfaces:

  • RF : 2 x RP-SMA connectors
  • Serial: Logic level TTL (+3.3v nominal, +5v tolerant)
  • Power: +5v, ~800mA max peak (at maximum transmit power)
  • GPIO: 6 General purpose IO (Digital, ADC, PWM capable).

Specifications:

  • Frequency Range:  902 – 928 MHz (USA) / 915 – 928 MHz (Australia)
  • Output Power: 1W (+30dBm), controllable in 1dB steps ( +/- 1dB @=20dBm typical )
  • Air Data transfer rates: 4, 8, 16, 19, 24, 32, 48, 64, 96, 128, 192 and 250 kbit/sec ( User selectable, 64k default )
  • UART data transfer rates: 2400, 4800, 9600, 19200, 38400, 57600, 115200 baud  ( User selectable, 57600 default )
  • Output Power: 1W (+30dBm)
  • Receive Sensitivity: >121 dBm at low data rates, high data rates (TBA)
  • Size: 30 mm (wide) x 57 mm (long) x 12.8 mm (thick) – Including RF Shield, Heatsink and connector extremeties
  • Weight: 14.5g
  • Mounting: 3 x M2.5 screws, 3 x header pin solder points
  • Power Supply: +5 V nominal, (+3.5 V min, +5.5 V max), ~800 mA peak at maximum power
  • Temp. Range: -40 to +85 deg C

Software / GCS Support:

The software solution is an open source development called “SiK” originally by Mike Smith and improved upon by Andrew Tridgell and RFDesign. A boot loader and interface is available for further development and field upgrade of the modem firmware via the serial port.

Most parameters are configurable via AT commands, Eg. baud rate (air/uart), frequency band, power levels, etc., please see the 3DR wiki for commands below for now.

V2.x firmware has been updated to support multipoint networking on the RFD900.

V1.x (non multipoint) is suitable for point to point links – the sourcecode is located at:   https://github.com/RFDesign/SiK

The user manual / datasheet can be found here : RFD900 Datasheet

A software manual for SiK firmware is here : RFD900 Software manual

RFD900 configuration tool: http://rfdesign.com.au/downloads/

RFD900 binary firmware repository: http://rfdesign.com.au/firmware/

3DR/RFD900 compatible configuration tool : http://vps.oborne.me/3drradioconfig.zip

Wiki for the 3DR radios (RFD900 has same commands): http://code.google.com/p/ardupilot-mega/wiki/3DRadio

Integrated support for configuring the RFD900 radios is supported by APM Planner, with other GCS solutions in development.

The default settings are at 57600 baud, N, 8, 1, and 64k air data rate.

Software features include:

  • Frequency hopping spread spectrum (FHSS)
  • Transparent serial link
  • Point to Point, or Multipoint networking
  • Configuration by simple AT commands for local radio, RT commands for remote radio
  • User configurable serial data rates and air datarates
  • Error correction routines, Mavlink protocol framing (user selectable)
  • Mavlink radio status reporting (Local RSSI, Remote RSSI, Local Noise, Remote Noise)
  • Automatic antenna diversity switching on a packet basis in realtime
  • Automatic duty cycle throttling based on radio temperature to avoid overheating

website, http://rfdesign.com.au for more information.