Launch Announcement XABEN-165 - Suffolk - Thursday 2nd July

[Steve]

Hi Folks - just a heads up that I'm planning a balloon launch Thursday
PM from the Ipswich, Suffolk area.    This is a LoRaWAN only flight -
mainly to give LoRaWAN a try for tracking latex up-down flights.

I've spent some time adding temperature/frequency correction to the
tracker software. Using the temperature sensor onboard the SX1276 to
apply a correcting frequency offset on each packet - this should ensure
the packets are close to the intended LoRaWAN channel frequencies. 
Un-corrected I did notice a considerable shift (35KHz) shift over the
HAB temperature range.  On the bench at least the corrected frequency
seems spot on, but if anyone with an SDR can keep an eye on frequency as
the flight progresses I'd appreciate it.

The flight should be on both spacenear as "xttn" and ttnmapper under the
"XABEN" project

https://ttnmapper.org/experiments/?experiment=XABEN&startdate=&enddate=&gateways=on&lines=on&points=on

I have to say I've been amazed at some of the distances turned in during
testing in the upstairs window of my house.  There seem regular periods
when the tracker is being received 200 - 400Km away by coastal LoRaWAN
gateways in Belgium and the Netherlands. This is due to "tropo sea
ducting" common this time of year I'm told.

There was one packet received 1145Km away in Vienna TTNmapper claims -
I'm struggling to believe that - I need to investigate further. Ignore
the line shown to 0,0 lat/lon as this is when my node is booting.

As its a LoRaWAN flight it can't be received by Dave's LoRa gateway
software - but if you wish, it is possible to run a LoRaWAN packet
forwarder on the PITS gateway hardware - the software is available here:

    https://github.com/bokse001/dual_chan_pkt_fwd

and you will need to create an account on The Things Network
(https://www.thethingsnetwork.org/) and set up a gateway/packet forwarder.

there is a tutorial here:

    https://www.youtube.com/watch?v=Ya-QlEaonLU

LoRaWAN uses 8 channels:

    867.1, 867.3 867.5 868.7 868.9, 868.1, 868.3, 868.5MHz

Full LoRaWAN gateways receive all 8 channels at once and several
spreading factors simultaneously (very cleaver) - obviously PITS
hardware can't do that - it can receive a single channel at a single
spreading factor (or two of you have 2 x 868MHz RFM95W modules).  If you
want to receive my tracker I suggest sticking to one of the 3 higher
LoRaWAN frequencies at SF12.

    Steve G8KHW



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[robert rushbrooke]

Hi Steve. 

Thanks for the heads up. I am interested in LoRa so I will set up the SDR and see what I can receive. I'm based on the coast in Northumberland and there has been some excellent tropo ducting recently. 

Good luck with the launch. 

Regards. 

Bob. 

M0KLO. 

Sent from Yahoo Mail on Android

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[Medad rufus]

Nice! all the best

Medad

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[John Laidler]

Steve,

I've got a Raspberry Pi powered LoRaWAN gateway which I've just configured to run at 868.7 SF12. It is connecting to the ThingsNetwork but is that all it needs to do or do I need to do something else to link it to the HABUB tracker?

Being in South Devon I'd be surprised if I receive anything but I'll point my eBay Yagi in your general direction on Thursday afternoon.

John 

On Tue, 30 Jun 2020 at 14:38, Steve <st...@randomaerospace.com> wrote:

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[David Akerman]

There's a TTN --> habhub gateway which I assume Steve is using as he said the flight will appear on spacenear.us.

Dave

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[Steve]

Yes I forgot to mention that - it's an original RPi model B (I knew I would find a use for it one day) that sits on my network bridging TTN and habitat 24x7 for this application.  After some timeout tweeking its been running flawlessly for a couple of months.

see:

    https://revspace.nl/TTNHABBridge

for details.

Thanks to Bertrik Sikken who wrote it and Medad for pointing me in the right direction.

    Steve

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[Ben Z en de rest]

Hi Steve, hope you have a good flight with lots of receivers and good last fixes :-)

Did you setup the ttnmapper as integration in your application ?  That gives a "track" possibility which includes the receiver's distance achieved during the flight .

I tried this url https://ttnmapper.org/track/?device=xttn&startdate=&enddate=&gateways=on&lines=on&points=on but that does not show information for your application.

Ben

Op di 30 jun. 2020 om 20:05 schreef Steve <st...@randomaerospace.com>:

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[Stuart Robinson]

If this is a LoRaWAN flight, on the standard LoRaWAN\TTN frequencies, how would you be able to monitor it with an SDR for frequency shifts, there would likley be a lot of other activity on the same frequencies ?

[Steve]

Perhaps, but surprisingly little LoRa that I have seen round here - LoRa is quite easy to distinguish from all the other 867/868 activity - I would have thought they would have been reasonably evident especially with a yagi and or rural location.

I was expecting the new positions to pop up reasonably quickly on the TTNmap ? - and thus folk would know when a new packet had been received.  Data seems to make its way from the receiving node to the TTN console almost instantly - but I'm not sure how long it would take to get to the TTNmap  - spacenear lags behind by anything up to 15 seconds.

    Steve

On 30/06/2020 22:35, Stuart Robinson wrote:

If this is a LoRaWAN flight, on the standard LoRaWAN\TTN frequencies, how would you be able to monitor it with an SDR for frequency shifts, there would likley be a lot of other activity on the same frequencies ?

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[Steve]

I've had a message from someone questioning if a balloon launch is
allowed under the current Covid restrictions.  As far as I know in
England I can as long as it's all an outdoor activity (pretty much the
definition of HAB) and as long as your not meeting in groups of more
than 6, not traveling together (unless in the same household) and social
distancing correctly etc

If I do chase the flight I can now travel any distance for an outdoor
activity.

I know some of the rocketry events aren't going ahead right now - but
that's because they are organized meetings of more than 6 people.

Personally I'm not planning on meeting anyone outside my immediate
family for the foreseeable - so I'm not expecting to be involved with
anyone else's balloon launch for some time to come.

I'd be interested if anyone reads a different view into the current
restrictions.

    Steve

[Steve]

Thanks Ben - frankly I'm not 100% sure what I'm doing on TTN - but mostly it seems to make sense.

yes it shows I have a ttnmapper integration on that application - is there something I need to do to enable "track"?  or perhaps its not showing a track because the transmitter hasn't moved its position yet?

    Steve

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[Stuart Robinson]

On Tuesday, June 30, 2020 at 11:47:42 PM UTC+1, G8KHW wrote:

If I do chase the flight I can now travel any distance for an outdoor
activity.

Stay out of Wales.

Although the often mentioned 5 mile 'rule' is not a rule at all just a guidline.

 

[Steve]

Very wise.   In any event an East coast sea landing is much more probable.

    Steve

On 01/07/2020 17:05, Stuart Robinson wrote:

On Tuesday, June 30, 2020 at 11:47:42 PM UTC+1, G8KHW wrote:

If I do chase the flight I can now travel any distance for an outdoor
activity.

Stay out of Wales.

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[Nick McCloud]

On Wednesday, 1 July 2020 17:05:28 UTC+1, Stuart Robinson wrote:

Stay out of Wales. 

Is that a personal request or a recommendation? ;-)

As for flights during Covid-19 restrictions, we are allowed to go about our normal business and as you say, it's not like you're gathering crowds all tightly pressed against each other unlike a beach or a rave or similar.

If I can find my Yagi I'll point a gateway in your direction. 

[PE2BZ]

Hi Steve,

could you give your device address ? That way I can filter it on my gateway traffic and see if it shows up.

Grtz,
Ben

[Stuart Robinson]

Plenty of coverage @13:21.

What Spreading Factor is in use ?

[John Laidler]

SF12 from the original email.

On Thu, 2 Jul 2020 at 13:21, Stuart Robinson <stu...@loratracker.uk> wrote:

Plenty of coverage @13:21.

What Spreading Factor is in use ?

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[Steve]

XABEN-165 successfully recovered this evening - very easy recovery.   The payload landed just a mile inland,   really tense watching on the tracker as it didn't look like it was going  to make it back to land.  If the balloon had burst a couple of minutes earlier it would have landed in the sea.

    Steve

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[John Laidler]

It was really tense watching it! 😀 Was it still transmitting on the ground? 

If I may are you going to share technical and code details? I've found a description of a tracker using an Arduino Mini but I suspect it may not work at high altitude as it was tested on a bicycle. 😀

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[Marcel Frans (PD9MRF)]

Hi John

 

We built this arduino pro mini  https://www.thethingsnetwork.org/labs/story/lorawan-gsp-tracker
The only thing we changed for a good altitude is  

  coords[8] = altitudeGPS >> 16;

  coords[9] = altitudeGPS >> 8;

  coords[10] = altitudeGPS >> 0;

 

There are more lorawan projects on github, almost doing the same as the above

 

GL

 

Marcel (PC4L)

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[Stuart Robinson]

A suggestion I would make is that you try to see if you get acceptable range at a lower spreading factor, a lower spreading factor gives shorter packets and allows for more air time. 

SF12 does of course give the longest range and Gateways hundreds of km away were picking up the xttn signals.

The TTN fair access policy, for free use of their infrastructure, allows you 30 seconds of air time per day, which can be restricting, particullarly at the higher spreading factors.

There is also the duty cycle limit of 1%, where again using the higher spreading factor packets can be quite restictive.

[John Laidler]

Marcel,

Thank you, that was the one I found but Arduinos and their code is all new to me and I hadn't a clue how to alter the code.  Many thanks. I will have a look at making one but I will probably be back with more questions!

John

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[Stuart Robinson]

Whilst you will find plenty of examples out there for TTN mapper nodes, most that I have seen just use the GPS as is.

For use with a high altitude balloon you need to configure the GPS for high altitude mode.

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[Steve]

I guessed this might come up:  so I had spent some time checking into the UK duty cycle and LoRaWAN limits and mulling it over.  The flight was designed to keep within the regulatory duty cycle limits - but it bust the LoRaWAN airtime limits.   Here is the rational:

Regulatory limits: LoRaWAN channel frequencies 868.1 868.3 and 868.5MHz fall into one EU band and the channel frequencies 867.1 867.3 867.5 867.7 and 867.9MHz into a different EU band - both have a duty cycle limit of 1%.  I made sure that I didn't break the duty cycle limits in either band - but that gave me overall 2% airtime to play with.

The packet rate used was adaptive and at its lowest in the middle of the flight and highest above 36Km - the duty cycle limits are defined as per hour without defining where the hours start and end - that also gives some flexibility.

The packet rates were chosen to keep within the regulatory duty cycle limits throughout the flight.

LoRaWAN: The SF12 packets were chosen for range, as a small part of the reason for the flight was to try for the LoRaWAN distance record,  also for recovery on the ground I wanted to give myself the best chance if it landed in a radio dead zone.  The packets are pretty much minimal GPS - and the TTN data page estimated the airtime at 1.1 seconds, so I know that over the course of the flight it will have broken the 30 seconds per day LoRaWAN airtime limit. 

In my defense I would say that other people attempting the distance record have also ignored that limit and I don't see why I should be at a disadvantage if I want to attempt it (as long as I'm not breaking the regulation).

Other thoughts on the experience: I agree that in normal operation for balloon tracking a lower SF and hence shorter packets would be more than adequate.  Maybe to get the most out of the system adaptive SF would be the way to go.

I sill have reservations about using LoRaWAN for latex up-down balloon tracking.  In the air for tracking you can't argue - the coverage is massive - I don't think a packet was lost over the entire flight above 500m.  However on the ground at launch and recovery locations there are a couple of things that are a pain:

    a) the channel hopping   b)  the need for internet coverage.

The channel hopping either means you have to have an expensive full LoRaWAN gateway - or several single channel packet forwarders set to different frequencies - either way more cost than needed.

Because LoRaWAN packets are encrypted you can't decode them on a gateway - this means that the gateway needs internet coverage in order to get the packet to TTN for it to be unencrypted and hence find the GPS location of the transmitter (and get it back to you).  In some rural locations this will be a challenge.  At the launch site yesterday coverage was iffy and I had to loft my hotspot in order to determine the GPS had locked before launch.  Likewise I was lucky the landing location had mobile internet coverage.

I think some form of mixed system would be best - with plain LoRa on the ground and LoRaWAN in the air.  That way a cheap single channel receiver could be used on the ground - switching to (or adding) LoRaWAN transmissions once in the air.

    Steve

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[David Akerman]

Absolutely agree re mixed system.  You could easily do pretty fast SSDV with UKHAS telemetry in between the LoRaWAN packets.

FWIW I asked on Twitter a while back about LoRaWAN "fair use" DC limits with a view to choosing a good scheme for HAB, and got a PM saying that they are routinely ignored.

Dave

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[Nick McCloud]

On Friday, 3 July 2020 14:29:19 UTC+1, David Akerman wrote:

FWIW I asked on Twitter a while back about LoRaWAN "fair use" DC limits with a view to choosing a good scheme for HAB, and got a PM saying that they are routinely ignored.

Overall the activity of Ben & Steve thus far is certainly "fair game" and of useful investigative work and it's clear some further flights will be required to tune the setup.

But as we are effectively using other peoples receivers for a unusual application without explicit permission, moving to a mixed-mode transmission so we stay within the fair use policy asap would be good neighbourliness.

Maybe we could go with it cycling around LoRa, SSDV, RTTY and LoRaWAN ....

[Stuart Robinson]

Thanks for the reply.

Its a more tricky (staying within legal duty cycle) on the software side if your using a standard TTN mapper tracker will do the job. You need here to assume the worst case, all packets in one band if using 'standard' TTN mapper software. The minimum packet size for a GPS location packet with temperature is going to be around 12 bytes so a TTN air time of circa 1.417secs, or sent every 142 seconds if the duty cycle limit was1% (@SF12 @BW125khz).

Not sure where the 1.1sec airtime comes from, for the flight the TTN logs a payload size of 28 bytes and an air time of 1.646 secs.

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[Steve]

The 1.1 seconds airtime came from the TTN console data page - see the bottom of this (shows a decoded packet):

    https://www.flickr.com/photos/16828840@N07/50090178401/in/dateposted-public/

If that's wrong not my fault.  In any event I doubt that the duty cycle limits were broken as I had allowed some headroom.

The choice of frequency and applying duty cycle is down to the device itself  - I had set up the duty cycles on each channel to ensure no more than 1% in each of the two EU bands and hence 2% overall. Hence the upper 3 frequencies (EU LoRaWAN channels 0 to 2) had a slightly higher probability of being chosen for transmission.  The choice of channel across the two bands is still random within that limitation.

Like I say my intention was to stay within the regulatory limits but not necessarily the LoRaWAN fair use.

    Steve

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[Stuart Robinson]

Thats about the right air time for the payload, which looks like 15 bytes, aboug right for lat,lon,alt,temp.

To get the full packet airtime you need to add in the 13 (minimum) bytes of header\addressing, so giving a 28 byte packet.

Not sure why the TTN console reported the airtime as 1.646s, the Semtech LoRa calculator suggests it should be 1.483s

[Steve]

Assuming Stuart's 1.483s figure is correct is correct:

At 1.483s per message the cycle time can be as quick as 71 seconds (allowing for the 1% + 1% duty cycle)

The cycle time up to 36Km was 96 seconds and 32 seconds above that.  The balloon spent 13 minutes above 36Km. I define the cycle time hour boundary to be half way through that period above 36Km.

That's 6.5 minutes on a 32 second cycle and 53.5 minutes on a 96 second cycle - giving about 45 or 46 messages in that hour = 78 - 80 second cycle time on average.  Therefore I didn't break the duty cycle limits.

I guess nobody expects the Spanish Inquisition.

    Steve

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[John Laidler]

I just enjoyed watching the flight! I did spot it was picked up by a node near Belfast which was an impressive distance. But I think I saw that was at an altitude of over 500m so it must have been on a mast.

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[Steve]

I enjoyed it - particularly as I got it back - which was a bit of a bonus.

I haven't done the post flight analysis of the data yet - there were certainly some reports over 750Km  but the longest distance is maybe being obscured by incorrect positions on a couple of gateways (one showing as being 9000Km away in Shenzhen China). 

https://ttnmapper.org/track/?experiment=xaben&startdate=2020-07-02

If anyone knows a way to extract the data ordered by distance (or a way of purging specific nodes from the data) I'd appreciate the pointer.

    Steve

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[Stuart Robinson]

Embarissingly the 1.483s figure does not appear to be correct.

I was using the SX1272 calculator that Semtech provide here;

https://www.semtech.com/products/wireless-rf/lora-transceivers/sx1262

However puzzled as to why the TTN logs say the air time was 1.646ms, I checks on an actual SX1272, using a example program that starts a time at the beginning of packet load and stops it when the TX_Done interrupt triggers indicating the packet TX has finished, that produces this output;

Packet> Hello World 123456 28 Bytes*  BytesSent,28  CRC,55E4  TransmitTime,1647mS

Which is very close to what the on-line calculator says (1646ms) when set for 28bytes;

https://www.loratools.nl/#/airtime

So my mistake ........ forgetting in the calculator to set optimisation to on !

[Steve]

If its 1.65 seconds the duty cycle is almost exactly on the on the 2% limit.

    Steve

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[Stuart Robinson]

Its certainly worth checking out and the air time is not linear to the payload size, it goes in steps. For the 1.65s air time you could have sent a further 3 bytes.

[PE2BZ]

Steve, if you refresh your track is the "way out of range" gateway now removed ?

Ben

[Steve]

Yes - thanks Ben - now working nicely - how did you remove them?

    Steve

On 10/07/2020 13:45, PE2BZ wrote:
> Steve, if you refresh your track is the "way out of range" gateway now removed ?
>
> Ben
>

[Ben Z en de rest]

Someone on the hab-nl facebook group knows someone who is related to the things network mapper. He mentioned that there is one problem with blacklisting, if the gateway in the future sets the position to a valid position, it is still blacklisted for ttnmapper tracks.

So, I just "dropped the question" and it was solved in 24 hours 😅

Op vr 10 jul. 2020 14:53 schreef Steve <st...@randomaerospace.com>:

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[Steve]

A video of the launch of this flight showing use of detaching cardboard de-reeler:-

    https://youtu.be/_y6QHyoPFaE

    Steve

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