LoRa LoRa Laughs!

Due to the restrictions on airborne amateur radio operation in the UK High Altitude Balloon (HAB) enthusiasts have been forced to utilise licence exempt low power devices in novel ways to make radio trackers for their payloads. I have written plenty on this blog about my HAB tracking, the UKHAS distributed listener network and my own flights.

Until recently the preferred method was to use RTTY transmissions, however the advent of the IoT (Internet Of Things) has seen manufacturers of radio modules develop devices to increase both the range and reliability of communication between ‘connected’ embedded devices.

One such development are LoRa devices, primarily for devices to connect to a global wide-area network LoRaWAN, more information can be found at the LoRa Alliance in addition there are some open hobbyist networks such as The Things Network using these devices.

Using chirp spread-spectrum modulation these LoRa devices are marketed as being capable of robust, interference and fade resistant communication over longer distances and higher data rates.

The UK HAB community has begun experimenting with these devices and one of their keen proponents is Dave Akerman (M0RPI). Dave has developed both payload software for the “Pi In The Sky” PITS tracker along with Anthony Stirk (M0UPU) and gateway software in collaboration with Robert Harrison M0RJX. The ‘gateway’ is the necessary receiver element to upload the data to the tracking system. (all software is on the PITS Github page)

Dave gave an informative presentation on LoRa at the UKHAS 2016 Conference which is now available online (starts around 3 minutes in)

I had intended to fly a LoRa transmitter on my 2015 Hamfest balloon but it stopped working at the eleventh hour and hadn’t done anything else with LoRa till recently.

Spurred on by the conference presentation and the fact more and more flights are carrying LoRa I invested in one of the Raspberry Pi expansion boards sold by Uputronics and built up another prototype tracker with a working LoRa module.

I have done talks at various radio clubs and societies and demonstrated it working but hadn’t actually received a ‘real flight’ as opportunities have been scarce due to the weather. However in the few weeks I have tracked a couple of flights receiving both telemetry and image data, getting a couple of complete images from the imaginatively named ‘SPACE’ flight.

Dave Akerman also flew a flight experimenting with multiple payloads using Time-division multiplexing (TDM). It had 10 small of “AVRLoRaNut” trackers (of Anthony M0UPU’s design) all set to the same frequency (434.450MHz) and same transmission mode. The trackers took turns to transmit, with each one allocated a particular transmission slot in a 20-second cycle. The cycle was GPS-timed but, if any tracker lost GPS lock then it derived timing from the transmissions from the other trackers (the LoRa devices are also receivers) All 10 trackers were suspended from the same balloon. This was in preparation for the ‘Operation Outward‘ re-enactment next year (Steve Randall gave a presentation on it in the above conference video starts 1 hour 16 mins in)

I successfully received telemetry despite the flight not being local and constantly heading away from me as can be seen in the screen shots.

Always a busy man Dave also flew a flight with an experimental camera setup. The SSDV images this time came from a Nikon compact camera, connected to the Raspberry Pi via USB, and using gphoto2 software to take and transfer images to the Pi where they were stored, resized and converted to SSDV format for transmission. These were large images with a high quality SSDV setting so lots of packets per image, approx 1400 per image in testing. 

This flight was using a 868MHz LoRa device, rather than the usual 434MHz due to the IR2030 restriction on bandwidth and duty cycle. Dave was using his Turbo-X or Mode 4 setting which is as fast as LoRa will go within IR2030 bandwidth restrictions (approx 8 packets / 2k bytes per second)

I hastily ordered a 868MHz device and soldered it in the spare slot on my gateway and built a collinear for 868MHz similar to the one I built for ADB-S reception (see video here).

You can see it lashed up just below the dual-band collinear – not ideal mounting and it wasn’t tested in anyway, built blind!  The less than optimal setup at UHF, the insane data rate and the distance (>100miles) were going to make reception difficult, so I was pleased I did manage to receive telemetry and image packets.

Most of the current LoRa development in the HAB community has tended to be on the Raspberry Pi due to the use with SSDV and the easy availability of cameras and ready built kit. LoRa is of course available on the Arduino platform and I had purchased a couple of ‘Dragino’ shields (pictured below) with a LoRa device on.

Dave has done some work on a AVR tracker software and a simple Arduino ‘Serial’ LoRa receiver. The receiver connects to a host PC appearing as a serial port and by running some gateway software the receiver can be configured via the serial link and received data is sent back to the gateway to be uploaded to the Habitat tracking system and SSDV system – the software can be seen here during the ‘Operation Outward’ test flight.

This gateway software is written in Pascal using Delphi and is not as functional as the Raspberry Pi Gateway software. Dave has made the source code available but I am not au fait at all with Delphi however I installed the free development IDE and intended to get in and make modifications but it seems to require a non-free(?) library for the serial comms so ditched the idea.

Instead I have spent the last few days developing a C# .NET version using Microsoft Visual Studio (the community version is free) and also have been modifying the Arduino code in the receiver to add functionality, such as storing the SSDV images locally.

It is still a work in progress but I have made a video showing the current state

Anyway as Cilla Black would say it’s been a Lorra Lorra Laughs!

My seemingly magic HAB antenna

Since visiting the UKHAS Conference and getting my Foundation licence I have come of out of my lull with a new found buzz and have been busy with my radio gear.

I have helped track a few more High Altitude Balloon (HAB) flights, uploading the received telemetry data to the Habhub server. Visit the UKHAS website for more information on how to become involved.

I am still surprised by the performance of the loft antenna I am using to receive the HAB telemetry. It was constructed as an experimental wide band antenna solution to use with my scanners back in 2007. I discovered some basic plans on the internet for this simple home brew antenna (originally hosted on a Geocities website, but is thankfully archived on Reocities here)

It is a modified bicone design and is constructed from nothing more than a couple of metal coat hangers fixed to a piece of pvc water pipe, with a 10m length of RG58 coax as the feeder. I used it successfully as a portable solution, mainly for airband listening and stuck it on top of a fibreglass fishing/flag pole when camping away at dog agility shows as these photos show.

Eventually it ended up being mounted up in the loft, suspended on a piece of string from the rafters and had largely been unused since I acquired a discone a few years ago.

When I first started tracking the HAB payloads I naturally used the discone but soon became frustrated by its variable performance and so tried this antenna instead and was amazed. Something appears to be just right with this antenna on 434MHz when used together with my FUNCube Dongle PRO+

I haven’t analysed why is seems to have such a sweet-spot on these frequencies and I am not touching it, moving it or even taking another picture of it in case it loses it’s magic properties! Remember these HAB flights are only 10mW and this antenna is under a slate roof!

On Friday (20-Sept-2013) Adam Cudworth (@adamcudworth) launched HABE-10 which involved a normal tracker on the balloon due to burst at around 35km along with a secondary tracker payload of a 3D-printed man that was separated at approx 27km, the two payloads being tracked separately as they fell to Earth. During the accent the main tracker also transmitted SSDV images from an on-board camera. Unfortunately this failed during the mission but some pictures were received before it did, as you can see I managed to successfully receive this 300 baud RTTY signal from home and uploaded packets to help reconstruct the images. The original images are at http://ssdv.habhub.org/HABE/2013-09-20



Friday afternoon also saw the launch of Leo Bodnar’s B-13 pico floater. Leo has become something of a HAB superstar following his amazing B-11 and B-12 balloons which broke the duration record for an amateur balloons (as reported on the Southgate ARC website) flying over many countries before contact was lost.

Sunday saw a launch of MOD-1 by Ugi, which again I received rather well as can be seen on this pie chart.

Today saw Steve Randall (G8KHW) launch two of his XABEN flights, XABEN-56 and XABEN-57. The main transmitters were on 434.250MHz and 434.300MHz and I was able to use the multiple VFO option of SDR-Radio.com V2 to track both launches, and as you can see from these pie-charts I made number three in the tracking charts! I achieved this while using a VNC connection to control the receiving station from work, just checking occasionally to correct for any drift in the frequency of the signal caused by the temperature variation of the transmitters.

Some more HAB tracking

I have been tracking some more of the High Altitude Balloons (HAB) that have been released over the last few weekends.

Last weekend (18th May 2013) saw the release of STRATODEAN2 from the Stratodean team, which I received quite well as can be seen from the telemetry stats.

Mark and Cassie have posted an update of the flight on their blog including an entertaining video

This weekend, there have been three more flights which I have managed to decode, track and update telemetry to the habitat website,

MONDO-12 which flew on Saturday 25th May 2013

BABSHAB which flew early this morning 

and finally this afternoon Dave Akerman’s PIE6, which used a Raspberry PI to preform the radio tracking. Details of the payload can be found here. In addition to the GPS the payload also contained a camera and the captured images were also transmitted using the SSDV protocol.

Each image is broken into smaller packets, while a receiver may receive all packets for an image it is unlikely it would receive all so by using the distributed network of multiple receivers the images are reconstructed on the habitat server. http://ssdv.habhub.org/

The screen shot below shows my PC as it receives the packets and attempts to reconstruct the image, hopefully you can see some portions of the image are missing.

Dave used a very fast 600Baud RTTY so he could transmit the high quality images, so was impressed to receive anything as the combination of SDR# and DL-Fldigi can be hard work for my ageing PC.

However these are all the images I contributed to (from the habitat site)

One thing I didn’t receive much of were the interlaced telemetry packets.

High Altitude Balloon Telemetry Updates

Several weeks ago I discovered the excitement of decoding high altitude balloon (HAB) telemetry.

As I blogged I spent a enjoyable couple of hours receiving the STRATODEAN project telemetry and submitting the received data to HABHubs habitat which is a system created to allow uploading, processing, storing and displaying telemetry and related information transmitted from the various high altitude balloons.

Mark and Cassie (the Stratodean team) have since uploaded a video on their blog showing the preparations, launch, flight and recovery of the payload.

Over the bank holiday weekend there were two other balloons launches planned, Chris Stubb’s (M6EDF) CHEAPO (webpage) and Steve Randall’s (G8KHW) XABEN-49 flights due.

CHEAPO did indeed fly, but sadly I didn’t receive anything as the signal was apparently very weak. I was also suffering some strong interference around the chosen frequency. I did have more success with XABEN-49 receiving a strong signal and a lot of telemetry packets. Though I did have to tweak the RTTY decode parameters in Dl-Fldigi, principally widening the shift and the filter widths, since the auto-configure option was setting it too narrow.

This morning the Essex Ham website has posted a nice video on their website explaining a bit more how to go about HAB decoding.

While investigating the habitat system I found the stats page and flight pie charts, showing the top receivers for each flight, I was pleased to see I featured quite high in the chart for the XABEN-49 flight, and indeed for the STRATODEAN flight last month.

XABEN-49 Telemetry Stats

STRATODEAN Telemetry Stats