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Topic: Issues with LoRa module and library (Read 628 times) previous topic - next topic

srnet

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.  
http://www.50dollarsat.info/
http://www.loratracker.uk/

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 :)

Thanks in advance

srnet

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 :)

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.
http://www.50dollarsat.info/
http://www.loratracker.uk/

edugimeno

#18
Mar 21, 2019, 07:21 pm Last Edit: Mar 21, 2019, 07:25 pm by edugimeno
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:
https://raw.githubusercontent.com/LoRaTracker/GPSTutorial/master/GPS%20performance%20comparisons/Pictures/GPS1A.jpg

srnet

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.

http://www.50dollarsat.info/
http://www.loratracker.uk/

edugimeno

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 :)

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!

srnet

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.
http://www.50dollarsat.info/
http://www.loratracker.uk/

edugimeno

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!!

srnet

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.
http://www.50dollarsat.info/
http://www.loratracker.uk/

edugimeno

See here;
https://ukhas.org.uk/guides:ublox6
Got it. I changed it and saved it. So it should be ready.

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

srnet

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.
http://www.50dollarsat.info/
http://www.loratracker.uk/

edugimeno

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...

srnet

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.

http://www.50dollarsat.info/
http://www.loratracker.uk/

edugimeno

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...:)

Working on the diy antennas now

Thanks!

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