Issues with LoRa module and library

Problem with high altitude balloons is the size of interference foot print they can create. Use full power and the signal will cover an area of around 1 million square kilometers. The same transmitter on the ground would only cause same issues over maybe 5 square kilometres.

The requirements for in flight tracking are threfore very different to the requirements for ground range searching. When the balloon has stopped moving, flip to higher power (if needed) and SF12, you will then have the range you need for ground searching, without the need for excessive power in flight.

srnet:
The requirements for in flight tracking are threfore very different to the requirements for ground range searching. When the balloon has stopped moving, flip to higher power (if needed) and SF12, you will then have the range you need for ground searching, without the need for excessive power in flight.

That's a good idea.
Anyone, I don't have any experience with LoRa out of the Ground-to-Ground scheme. And I'm getting distances of 6-10Km depending on the scenario.
Now talking about Air-to-Ground. Do you know, for a fact, that I will be able to pick these signals with no issue, even when the ballonn has already moved 100 km away, from the ground, at SF=7 with no problem? I don't have any way to test this other than risking to lose all the payload if I happen to actually lose the signal...

Thanks

Ok there's definitely something different on these boards.
Some days ago I started all my tests again with "basic" parameters, just in case:

SF=7
No CRC
No SyncWord
NO PABOOST

Today I kept experiencing the random loss of signal in the receiving lora device, even at short distances, of 3-5 ft
I added the RSSI measurement to the debug output in the RX. This surprised me:

At 3ft distance between antennas, I was getting RSSI of -125 to -135, and half of the times the payload was garbled

That's why I started suspecting my antennas. Because I have a bunch of them from older projects and I wasn't sure if they were 0.9 or 2.4GHz. So I removed the antennas, and soldered a 8.6cm wire to the ant pad, as this is a method that I've used in the past with very good range results

Still, no change. Same poor RSSI. Tried other BSFrance boards I have at home, both in the Tx and Rx side. No change. Tried these other boards with the wire antenna too. No change

Tried to re-activate PA BOOST.

BIG CHANGE. Rssi came down to -40 at short distance. -70 at opposite ends of the house.
Tried the subber antenna. Same result (So I guess they were valid).
So this makes me wonder why the power on this devices is so low until I activate the PA BOOST parameter.

Can any one explain what it does? Anything else than "unlocking" a higher power? Or does it change anything else?

Anyway I see that Im going to "fly" with this PABOOST parameter ON

edugimeno:
Now talking about Air-to-Ground. Do you know, for a fact, that I will be able to pick these signals with no issue, even when the ballonn has already moved 100 km away, from the ground, at SF=7 with no problem? I don't have any way to test this other than risking to lose all the payload if I happen to actually lose the signal...

I have had two way comms to a LoRa tracker on a foil party balloon @ 240km, @434Mhz, @10mW, @BW41700, @SF8, a record at the time, read about it here;

HAB Tracking at Breakfast

Distances of 400km and 500km have been reported in the UK, where we are limited to 10mW.

If you unsure, just arrange to be able to remotly configure the tracker so that you can change the power levels to suit etc.

WOW!!! So I'm definitely aiming too high if that's the case.
The thing is, like I said before, once you release the balloon there's no way back (you know this), so if things don't work like you expected, the whole project is gone...

With this I mean that I would try to get the code and everything as simple as I can. I may pick a SF a little above what I would expect to be valid and try to use the best antenna I can.

Now that you've done this before, let me ask you something if you don't mind.

What antenna did you use both for the payload and the chaser?
What GPS module did you use? I'm using for these tests the NEO-6M Ublox GPS but this one doesn't go beyond 18Km in height, so Im awaiting for a NEO-8M to arrive, which does go beyond 18Km.

Any help on this topic would be appreciated, Im a teacher collaborating with 9 kids in this school project and I can't fail with this :slight_smile:

Thanks in advance

edugimeno:
WOW!!! So I'm definitely aiming too high if that's the case.
The thing is, like I said before, once you release the balloon there's no way back (you know this), so if things don't work like you expected, the whole project is gone...

With this I mean that I would try to get the code and everything as simple as I can. I may pick a SF a little above what I would expect to be valid and try to use the best antenna I can.

Now that you've done this before, let me ask you something if you don't mind.

What antenna did you use both for the payload and the chaser?
What GPS module did you use? I'm using for these tests the NEO-6M Ublox GPS but this one doesn't go beyond 18Km in height, so Im awaiting for a NEO-8M to arrive, which does go beyond 18Km.

Any help on this topic would be appreciated, Im a teacher collaborating with 9 kids in this school project and I can't fail with this :slight_smile:

Thanks in advance

Balloon tracker uses a 1/4wave vertical (pointing downwards) with 1/4wave radials made out of guitar wire. Ernie ball custom gauge 13.

My base station antenna is a Diamond X50N, its got most of its gain at a low angle to the horizon, which is where you want it.

For a chaser, normally a small mag mount on a car around 5dBi. For ground based searching I use an Arrow satellite 7 element yagi, brillant antenna.

The Ublox GPS should work above 18km, at least the geniune ones should when configured. In the UK the Ublox MAX8Q is common for HAB flights.

There are alternativces to the Ublox GPSs that are heaps cheaper, see this report on GPSs;

GPS Performance Comparisons

Although I have not tested the Quectels at altitude yet.

I really appreciate all your info about antennas. I will start building them soon.
About the GPS model, why did I read somewhere that the 6M is limited to 18km? Also in the page you point to, it states "all 3 have a high altitude mode allowing operation above 18,000M"
So is this something that can be activated thru serial commands in the module?

The problem is like before...I need to be 100% sure they do work, I can't test before.

The 8M modules are on its way anyway

I get really bad times for first fix (with a partially clear view from a terrace), sometimes above 5mins for first fix, Im using this small rectangular (like 3cm x 1cm) antenna, hopefully the 8M comes with the larger square antenna

Now I realize the guy in the article mentions "No fix" with the 6M module and small antenna. That's my configuration now, no wonder why it takes so long..it didn't even work for him.

Thanks!!
Edit: With the small recxtangular antenna I refer to 3B on this picture, and large square is 3A on this picture:

The geniune Ublox 6 GPS, and there are fakes out there, should be configuarable by serial command for operation up to 50,000M.

See the 'Navigation Configuration Settings Decription' part of the receiver protocol datasheet.

Extended fix times on the ground are not a show stopper, as soon as the balloon rises a few hundread feet in the air its view of the horizon ands hence GPS normally improves.

The Quectel GPSs had a noticably better signal performance than the equivalent Ubloxes, see the charts and fix times in the report.

Ok, yes I read about fake chips. I know there's a program out there to configure the Ublox modules, but mine is already soldered to the LoRa Board, do you know if using a serial-bypass I can configure all the parameters in the GPS?

Yes that's true, once above the ground the GPS will get much better signal, but for these tests at home the fix time is really annoying :slight_smile:

For now Im sticking to this module, we are planning for a pre-final test launch shortly and purchasing another GPS would probably get into a timing issue.

Thanks!

edugimeno:
I can configure all the parameters in the GPS?

Configure it over serial, either from Arduino or using Ubloxes Ucenter utility.

Details of configuration for high altitude mode, are in the navigation configuration part of the GPSs protocol description manual.

srnet:
Configure it over serial, either from Arduino or using Ubloxes Ucenter utility.

Ok I uploaded the "SerialPassThru" sketch to my arduino, downloaded the Ucenter tool, and it does connet well to the GPS with the Arduino in between.
All I have to change is in NAV5 switch from Dynamic Model->0-Portable to 6-Airborne<1G?

Is this it? Is there any way to actually confirm that these GPS is fully capable of >18km=

Thanks a lot!!

edugimeno:
Ok I uploaded the "SerialPassThru" sketch to my arduino, downloaded the Ucenter tool, and it does connet well to the GPS with the Arduino in between.
All I have to change is in NAV5 switch from Dynamic Model->0-Portable to 6-Airborne<1G?

Is this it? Is there any way to actually confirm that these GPS is fully capable of >18km=

Thanks a lot!!

See here;

https://ukhas.org.uk/guides:ublox6

Testing the GPS is easy, you put it on a high altitude balloon and if its not configured right it will stop working once it reaches a certain altitude.

srnet:
See here;
https://ukhas.org.uk/guides:ublox6

Got it. I changed it and saved it. So it should be ready.

srnet:
Testing the GPS is easy, you put it on a high altitude balloon and if its not configured right it will stop working once it reaches a certain altitude.

Haha yes I know, but as you know for that I need a permission for each launch, a balloon/parachute, etc...Anyway we're doing our pre-final launch within one month.

I have several types of batteries. I've heard that Li-xxx batteries are the best for cold wetaher. I have lots of LiFePO4 batteries but they are rated at 3.2v and in this board there's a LDO 3.3v regulator which will surely turn off slightly above 3.3, too close to its nominal voltage.

I will probably switch to LiPo batteries, with a nominal voltage of 4.2v. Other option is non-rechargeable batteries like Energizer Lithium 1.5v batteries but I would need at least 3 of these to reach the minumum voltage for the regulator.

Which route did you take on this subject?

Thanks again

edugimeno:
Which route did you take on this subject?

Well, one of the batteries you mentioned is used quite often.

Ideal mini project for class I would have though, which batteries are good in the cold.

Chuck them in the freezer for a while, insulate them so they stay cold, and then measure the voltage under load.

srnet:
Well, one of the batteries you mentioned is used quite often.

Ideal mini project for class I would have though, which batteries are good in the cold.

Chuck them in the freezer for a while, insulate them so they stay cold, and then measure the voltage under load.

Hey I'm not a student, I'm their teacher!! LOL

They are already working on lots of other matters related to this, and they are building an arduino datalogger that stores X/Y, altitude, temperature, pressure and other data in a SD card to get the data when the payload is recovered.

But I offered them to build the gps tracker by myself, it seemed too much for them.
I would test what you are saying, but Im expecting -50->-60ºC up there but freezers here don't usually go under -15..-20ºC...

edugimeno:
I would test what you are saying, but Im expecting -50->-60ºC up there but freezers here don't usually go under -15..-20ºC...

Sure, and the feeezer in my house only goes down to -17C.

But its a start and -17C is at least an indication of what might happen at much lower temperatures.

I will probably use 3xAA Li Energizer batteries. I've seen a tutorial (probably yours) where 2xAA batts were used after removing the on board regulator and disabling the low-volt detector, but I don't want to modify this board. 3 batts is only 15 gr more than 2 batts, removing the regulator saves some power but I think this setup would still last several days...all I need is 6-8-h...:slight_smile:

Working on the diy antennas now

Thanks!

So I know this is terrible thread necromancy, but I didn't see an answer to this question and thought it may help others who get stuck wondering why something isn't working and they turn on PABOOST and BOOM it starts working.

If you look at the reference designs for many of the lora radios, they often have 2 or 3 RF outputs and 1-2 RF inputs. The RF inputs are generally either broadband (if there is one) or split into two bands (if there are two). The outputs are generally split between low and high frequency bands and each of those outputs will be from a high efficiency PA (but it can only produce maybe 10-17dBm as a maximum) and a wideband higher output PA which is usually labelled PA_BOOST, this one might be capable of 20-22dBm.

"But there is only one antenna port" I hear you say - well, either a lumped model matching network is used to join them together, or there will be RF switches onboard. Usually the high and low bands are split to different antennas, but in each case the TX/RX is usually switched, and this switching can be broken out and under the control of the microcontroller, or can be controlled by the lora chip directly.

When a radio board is laid out using PA_BOOST as the TX chain for a particular frequency range - the corresponding high efficiency, lower power PA line is generally left floating.

So the reason you were getting terrible dropouts was - your board is laid out to use the PA_BOOST pin for the TX path, and the alternative pin was floating and hence had no matching network, no antenna connected etc - it was radiating directly from the pin on the board (you are lucky you could connect at all!!).

I hope this helps someone else out there who is confused as to why they need to set this parameter on their board for it to work.

Most all of the UHF LoRa modules use PA_BOOST as default.

If the claimed maximum power output is 20dBm, the module is using PA_BOOST and this is the default setting for most libraries so you dont need to set it.

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