Launch Announcement - 16th July 2024 - Wantage/Abingdon

[Russell Hills]

Hi all,

We are planning a Mar Balloon launch from the Wantage/Abingdon area, around 10-11AM BST, expected to head in a east-southeasterly direction. Aiming for 30km altitude, expected flight duration of ~2 hours.

We are using a LoRa Flextrak tracker, Mode 1, 434.218MHz, any support tracking would be greatly appreciated.

Cheers!

[Mark Jessop]

I'm curious what the MARS2024IR payload was?

Its telemetry looked to be uploaded using some custom script (using our pysondehub library). Was this a different radio link?

73

Mark VK5QI

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[Russell Hills]

We have a second tracker using a RockBlock Iridium modem which pings the position to an email, and we are using a python script to scrape the email for messages, formatting them and uploading them using the pysondehub library. It's pretty useful for finding the exact landing site after it has dropped below the radio horizon for the LoRa receivers.

[Gavin Gill]

That’s awsome,

Assumidly there is some sort of subscription to use iridium?

Kind Regards,

Gavin Gill

Ga...@me.com

+44 (0)750 1190 786

Sent from my iPhone

On 16 Jul 2024, at 13:22, Russell Hills <russell.an...@gmail.com> wrote:

We have a second tracker using a RockBlock Iridium modem which pings the position to an email, and we are using a python script to scrape the email for messages, formatting them and uploading them using the pysondehub library. It's pretty useful for finding the exact landing site after it has dropped below the radio horizon for the LoRa receivers.

To view this discussion on the web visit https://groups.google.com/d/msgid/ukhas/529a7e3a-c00b-4572-9397-9b885e2989bdn%40googlegroups.com.

[Gavin Gill]

I am officially a contributor, so thank you for the launch 🤣 (a whopping 17 Pakets)

I have a few questions, assumidly both trackers are on the same payload? How come they have different predictions?(one might be slightly delayed but they currently have different landing predictions Miles out)

What causes CRC errors, is it bad antenna placement / not receiving strong enough signal?

I am getting the following errors 

Kind Regards,

Gavin Gill

Sent from my iPhone

On 15 Jul 2024, at 20:33, Russell Hills <russell.an...@gmail.com> wrote:

Hi all,

We are planning a Mar Balloon launch from the Wantage/Abingdon area, around 10-11AM BST, expected to head in a east-southeasterly direction. Aiming for 30km altitude, expected flight duration of ~2 hours.

We are using a LoRa Flextrak tracker, Mode 1, 434.218MHz, any support tracking would be greatly appreciated.

Cheers!

--

[Russell Hills]

Yeah, there's a monthly 'line rental' (£13 per month plus VAT), plus each message costs one credit, which costs between 5p-15p each depending on how many you buy at a time. We only transmit at 2min intervals, so don't get through that many.

[Ross G6GVI]

Yes Gavin, those decoding errors can be due to either a poor SNR or a frequency offset (the low-cost reference oscillators may give an error of 10kHz or so). But I see from your screen that you'd earlier locked onto the signal with your AFC, so the later errors are probably be due to the signal dropping into the noise.  In addition to receiver (thermal) noise, co-channel interference from other ISM band signals can be a problem and limit the reception.

I just set up a temporary yagi antenna for tracking each flight and always use a masthead preamp to overcome the feeder losses. I hadn't put my 7-ele in a good enough position this morning, so didn't receive anything of the first half of the flight. But after lunch I managed to get my 12-ele up on a temporary mast in the garden later and caught some of the later part.

It gave me an opportunity to compare two of my receivers: an old TTGO board (running via USB to HAB Base) and the LoRa Gateway with an Ra02 on a PiZero 2W. They were both fed via a splitter from the same antenna feed and the TTGO was doing rather better than the Ra02 (478 packets compared with 352).

Regards from Ross (in Bolton, in a valley >200km away)

[Russell Hills]

Yeah both trackers are on the same balloon, I don't know enough about how the SondeHub prediction works, but I would assume that it has something to do with the fact that the Iridium data points are very far apart in time (in theory they should be every 2 minutes, sometimes it's a bit more if the messages don't go through first time).

[Russell Hills]

Thanks everyone for support during the flight, we had 11 other receivers helping track us, as far away as France and the Netherlands.

We reached an altitude of 33.6km, landed in a tree (for the first time in 5 flights), but have managed to recover it!

Now we just need to do it again in the next few weeks, if the weather decides to play nicely again....

[Steven]

Ross,

It looked as though your frequencies reported were significantly lower than the rest of the pack (from Grafana). Any reason for this? I think you were around 434.210 vs ~434.220

Steven

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[Ross G6GVI]

Yes Steven, that frequency error (of around -9kHz) is due to the onboard ref oscillator on the TTGO board which I was using for G6GVI-B.

It's running Dave's "LoraBluetooth" code, but via a USB connection to the HAB Base program and doesn't have a "PPM" facility to correct the error.

If Jack G8HIK had been on, he'd have had the same issue (but with an error of -4kHz), as he uses the same setup.

However I was able to present a more accurate frequency from my G6GVI-Z receiver, whose Lora Gateway software does include the PPM correction (which I have calibrated).

Regards from Ross.

[David Akerman]

I'd better add a PPM setting then :)

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[David Akerman]

I've updated HAB Base and added a PPM setting for LoRa USB serial receivers.

New installer V1.7.8: https://github.com/daveake/HABBase/releases/tag/V1_7_8

To adjust PPM open the settings for the USB LoRa receiver.  First attached pic shows the settings page.

If you're using my LoRa Serial/Bluetooth receiver firmware, that supports connection of a small OLED display which shows the current settings and latest packet.  That will show the frequency adjusted by the PPM setting, since it doesn't itself have a PPM adjustment.  At some point I'll add PPM support to it so that it can display the actual frequency not the adjusted one.

Dave

[David Akerman]

PPM adjustment included (and SH upload now excludes the PPM adjustment) in V1.7.9:

https://github.com/daveake/HABBase/releases/tag/V1_7_9

Dave

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[Gavin Gill]

Hi Ross,

Thank you for a very detailed explanation.

Do you think my current setup may be hindering my signal quality? (Image attached) do I have too much going on? I have the uputronics wideband preamp. https://store.uputronics.com/index.php?route=product/product&path=59&product_id=102

Annexed to an 6 way splitter,And then a tbeam running cubesat, A raspberry pi with autorx, pi running Lora gateway(2 x 433 slots) and lastly pi running horussemodlib.

That being said I am only using a small nooelec sdr 433 antenna on a windowsill, next month I’ll be swapping it for an x50n outside. So hopefully that will help with things!

Kind Regards,

Gavin Gill

Sent from my iPhone

On 16 Jul 2024, at 15:03, Ross G6GVI <ross....@gmail.com> wrote:



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[Ross G6GVI]

Thanks Dave, I've just tested V1.7.9 and it now correctly displays the frequency of my test-source (434.450):

(you can also see the warm-up drift of my Tx & Rx)

[Gavin Gill]

Sorry, with image attached this time!

On Wednesday, July 17, 2024 at 3:44:06 PM UTC+1 Gavin Gill wrote:

Hi Ross,

Thank you for a very detailed explanation.

Do you think my current setup may be hindering my signal quality? (Image attached) do I have too much going on? I have the uputronics wideband preamp. https://store.uputronics.com/index.php?route=product/product&path=59&product_id=102

connected to an 6 way splitter, And then a tbeam running cubesat, A raspberry pi with autorx, pi running Lora gateway(2 x 433 slots) and lastly pi running horussemodlib.

That being said I am only using a small nooelec sdr 433 antenna on a windowsill, next month I’ll be swapping it for an x50n outside. So hopefully that will help with things!

Kind Regards,

Gavin Gill

Sent from my iPhone



[Ross G6GVI]

Wow Gavin, that's quite a busy receiver console!

It's possible you may suffer some problems with all the (unscreened) hardware being in close proximity - harmonics of on-board signals falling in receiver pass-bands.

Is that splitter a 50-ohm or 75-ohm model? It may not work so well if it's mis-matched, but in any event should have a "dummy load" termination on that unused output. I use a 2-way splitter rather like this one if I need to run two receivers.

However the best place for the preamp is close to the antenna and it must have sufficient gain to overcome the losses in your feeder and splitter (-8dB for 6-way?). My preamp is a narrowband design (peaked for 430-440MHz), but that one you're using is wideband, so it could degrade the spurious rejection of your receivers.

Your best improvement is certainly to get an antenna outside in the clear. I'm located near the bottom of a valley, so I use a directional antenna, as it has more gain (and directivity, which helps to reduce co-channel interference problems) - but of course it needs to be pointed at the wanted signal each time!

Maybe the next time you're tracking a distant LoRa flight, connect your outdoor antenna straight to one of your Gateway inputs and see how it does? Then maybe swap over to the other slot mid-way, to compare their performance?

Ross

[Gavin Gill]

Thank you Ross,

Good shout about testing on next launch. 👍🏻

Also my splitter is 75ohm, doh! So I’ll look to replace that then… your splitter looks good, just a pitty it doesn’t come in a 5 way version 🤣

In terms of a dummy load, would I take an rf connector with a 75ohm resistor connecting pin and sheath together?

About to start my Essex ham course on Monday, hoping to get foundation license by August, and then start working towards my full licence, should brush me up on my knowledge!

Thanks for the help.

Gavin

Sent from my iPhone

On 17 Jul 2024, at 16:44, Ross G6GVI <ross....@gmail.com> wrote:



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