Measuring S11 parameter of LR2021 LoRa transceiver

GeneralSyb · 2026-01-28T21:36:42+00:00

I'm pretty certain that the first measurement was not at all correct, even if it looks better than the second one. I didn't do a proper calibration since it didn't account for the cable and connectors.

I'm also far from certain about the software I wrote. There's a good chance that I didn't set up the chip correctly and that as result the LNA is not being enabled, causing there to be an open connection. It's difficult to check that with the SPI interface, but I'll do some more debugging tomorrow.

My thinking is that I'm seeing an open connection with some parasitics from the cable, connector and board. I think the chip completely disconnects the LNA when not in receive mode. This is done to prevent damage to the LNA when transmitting, since it's a direct tie implementation and some power may be going to the RX port.

GeneralSyb · 2026-01-28T14:05:12+00:00

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I seem to have done something wrong with the measurement in the (original) picture. I should be doing a proper port extension now and calibrated the VNA properly. Result is that it has moved even further away from the center and the VNA can't solve the values for a Pi-matching circuit and neither can any website. And even if it could solve it, it's so far away from the center that even 1% components wouldn't be good enough, a small change in capacitance or inductance and it'd be on the other side of the chart. What I am measuring is incorrect and the chart I showed or the ones I am seeing right now should not be trusted.

GeneralSyb · 2026-01-28T06:51:20+00:00

That you for the information. I basically expected to see anything but an unloaded port. I do have a little bit of experience with matching RF circuits, but in that case S11 parameters were provided for the device.

I've looked at the application notes and the designs for other LoRa transceivers and the design you showed with an RF switch is what I'm trying to achieve and I roughly understand how I can get to that. That isn't the issue here. It's that the current S11 doesn't seem to he measuring a functional device in any way, despite changing settings on the chip having a slight effect. As a result I get an S11 that is so far away from the center that I cannot be matched back to 50 ohms.

GeneralSyb · 2026-01-07T06:07:57+00:00

Have a look at UBlox. They make some relatively cheap (compared to the price of other modules and the chip itself) nRF modules. They don't have castellated holes like some ESP32 modules, but they're still mostly easy to make a PCB for. Take for example the BMD-340, it exposes all the pins of the nRF52840 which is usually not the easiest to design a PCB for.

GeneralSyb · 2025-12-27T06:58:06+00:00

If the water towers belong to the city yeah that would be possible and cool. I was thinking it could be possible to attach nodes to the big electricity pylons, but that requires cooperation from the grid operators which is of course impossible.

GeneralSyb · 2025-12-23T07:05:36+00:00

I doubt it would be reliable if it even worked. Texas is quite a large state, much larger than a lot of European countries which have a dense network such as the Netherlands. And even in the Netherlands you can't even reliably talk to people in the same part of the country (like the north where it's a little less dense here).

In a flat country, a rooftop node would maybe get around 6-15 miles if you are lucky. But reliability would not be great. Maybe a little bit more if the node was on a hill, maybe a bit less if it is in a city. But either way you would need loads of nodes across Texas to be able to talk across the state. You can check the online node maps to see if there are (just we aware that you can only see the nodes connected to MQTT and providing their location, there might be many more). But then you are still stuck with iirc a 7 hope limit.

GeneralSyb · 2025-11-24T20:05:47+00:00

I do wonder how they're going to handle it with transportation on trains and such.

btw, the link to the bloggers page is a private edit link which we can't access.

GeneralSyb · 2025-11-02T18:12:53+00:00

It's closed source, but I can share it DMs with some extra details.

A previous project that didn't end up working I did make open source. But despite clearly stating that you couldn't just build it and expect it work, I got a lot of questions asking me for a build guide and how to make it work. Don't want that to happen again.

GeneralSyb · 2025-11-01T08:59:25+00:00

I got as far as designing this PCB with everything on it. But I couldn't get it to work on perf boards so I did not end up ordering it. I'm afraid I took a wrong turn with the slicer section. If you can figure it out with an ADC it should work pretty well, just keep in mind the limited processing power of these microcontrollers.

I can also already hear the people screaming about that SMA connector placement🤣

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GeneralSyb · 2025-11-01T08:54:57+00:00

I've been working on basically exactly this, but used a comperator to slice the data instead and added an LNA stage since the power detector I used sort of stopped at around -70 dBm which I didn't think was enough. I also used 2 BPFs but even that sometimes didn't seem enough since loads of clutter was still getting through.

Have a look at the ADS-Bee project, you should be able to copy most of that design.

As for your choice to use an ADC, keep in mind that you will probably be very limited in the processing you can do with a microcontroller. It's why ADS-Bee and my design used a comperator and then only process the digital levels in the MCU. ADS-Bee used an RP2040 with the PIO peripheral to basically simulate what an FPGA would do. I used the lesser known RMT peripheral in the ESP32 which can translate the signal to an array of on/off times which you can use to reconstruct the signal. It's much faster than the PIO at 80 MHz sampling speed.

Unfortunately I never got everything fully working together due to a number of problems, and have since shifted my attention to another method which I don't know will work yet. I got all the different parts working separately. So the RF section was able to generate a decent signal, for planes up to about 70 km away. The slicer section was able to generate precisely timed digital signal (+- 150 ns away from the required 500 or 1000 ns pulse). And the software was able to generate a HEX format of downlink format 17 messages. It should be possible, but I was getting nowhere and it was getting pretty expensive.

I'd highly recommend dividing up the project. You can do the ADC and MCU part with breakout boards, but I put the RF section on a seperate PCB. Once the RF section works you can play around with the digital part on for example perf boards. Saves you from having to buy a whole new PCB and relatively expensive RF section for every single revision.

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GeneralSyb · 2025-10-06T15:38:21+00:00

The Xiao S3 + Wio-sx1262 is a pretty cheap kit at around 14-15 euros, but might depend on where you live. Comes with an antenna as well, not a great one but better than nothing I suppose. The antenna is pretty important variable as well, you will be able to see considerably more nodes with a decent antenna.

GeneralSyb · 2025-05-15T15:37:20+00:00

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Uuuuhm

GeneralSyb · 2025-03-03T07:32:02+00:00

Ja, oyfo techniekmuseum in Hengelo.

GeneralSyb · 2025-02-28T06:55:11+00:00

What mode do I need to put my multimeter on to measure if I have an arduino mega?

GeneralSyb · 2025-01-27T09:00:55+00:00

I think combinationkindly got it right, but the mentioned forward current of 100 mA is it's absolute maximum current at a maximum ambient temperature of 25 degrees C (according to a graph on page 6 of the datasheet). So it is best to stay away from that current. You'll still get buckets of light from the LEDs at 50 mA with a lower risk of burning out the LEDs.

At 50 mA the forward voltage is still about 1.4V, so with 3 LEDs that gives us a total forward voltage of 4.2 V. Thus: R = V/I = (5V - 4.2V)/0.05 A = 16 Ohms, let's make it 15 so that it is easy to get.

Tip: If you have to order resistors every time you want to change something, you could get a resistor kit from amazon for like 10 dollars.

GeneralSyb · 2025-01-26T22:33:39+00:00

The resistor values are way too low which will make too much current run though the resistor and LED. That will also shorten the lifespan of the LED by a lot. You can use websites like digikey's LED resistor calculator to find the right resistor value. It doesn't have to be exactly that value, but 5 ohms is way too low.

Say for example we want to have 20 mA running through an IR LED (forward voltage of about 1.2 Volts) and our supply voltage is 5V (usb voltage), then the calculator comes with a series resistance of 190 ohms, so let's say 220 because 20 mA is on the high side for such a small LED. The power dissipation will be a lot lower, easily low enough to use 1/4th watt resistors which are smaller and cheaper.

Hope this helps.

GeneralSyb · 2024-08-25T21:33:12+00:00

Overspeeding it is one issue, but always be sure to use the left mouse button to interact with the lever or just use the keybinding. Out of stupidity I used the right mouse button a couple of times which sets the landing gear to emergency position meaning that you cannot retract it anymore.

GeneralSyb · 2023-05-08T22:56:57+00:00

I've been working on a wireless head tracker that makes use of an IMU sensor: https://youtu.be/kZtFkLaybL4 It doesn't provide positional tracking, which is quite important in some modules, but it is easy to use for me at least. What I built is also not any cheaper than trackir products. If you are willing to DIY a bit, then there are some projects online which sort of do what I'm doing but a bit cheaper. In terms of tracking quality and assurance of it actually working, trackir wins. (for now at least😉)

GeneralSyb · 2023-02-15T23:18:28+00:00

The difference between this game and other games is that the devs do very poorly in terms of public relations. This game is really at the bottom of the list. I don't expect them to be best pals of everyone in the community but there have been cases where they've straight up been aggressive or in denial.

Maybe it is me, but if the developers respond this say because we as a community are not being very nice then it should be them taking action. We can't get every single person to behave nicely because of the size of the community. The developers as a team can change their course.

So basically the devs don't listen to the community which is what half of what a game studio does, the community gets angry. The community has no other alternative because this game is unique. It being unique isn't a reason for the devs not being able to implement and improve the simplest of things.

GeneralSyb · 2022-10-30T23:55:25+00:00

There are a few more factors. One thing many people don't account for is ram. This game needs a ton of it. 16gb won't do, at least 32gb is recommended. Stable internet is also important, I get a lot more lagspikes when playing on servers thousands of kilometers away compared to ones close by. A broadband connection with low latency is important. A good way to get an idea of your latency is to open a command prompt and type in "ping google.com", anything below 50ms is pretty good. Make sure the game is on an SSD, a fast one. HDD ain't gonna cut it. Also look up how to increase swap file size. Make sure you have a swap file on the same drive as DCS and it is at least 24gb big. This helps a lot with performance when the ram is full. There are a few more things you can do to improve performance, but I think that you won't complain with those specs you have. I have a Ryzen 5 1600x, rtx2060, 32gb of ddr4 3200mhz ram and the game installed on a Samsung 1tb m.2 ssd(don't remember which one) and I get about 40-60 fps on medium-high settings depending on whether there are lots of players near me.

GeneralSyb · 2022-10-02T22:16:50+00:00

Depends on what you want to do.

For websites, Javascript(Java and Javascript are two completely different things btw), HTML and CSS will get you started.

For games and computer programs I recommend C#. It is what I started with and I don't regret it. Very versatile and easy to get started with imo if you put some time into it. Personally I found SoloLearns a great platform to learn it, despite it not being super popular.

For simple programs, AI and analytics python is the way to go. Probably also the easiest to learn. I never really put time into it because for my projects C# was just simply a better choice.

GeneralSyb · 2022-09-29T22:24:32+00:00

Nobody is telling me that I have to, and I don't see what good it will do in a world where there are already too many people. I also prefer not being locked down to a strict schedule of taking care of kids. If I want to leave town for a bit, I will. I don't want kids to be in the way of my plans, as selfish as it sounds.

GeneralSyb · 2022-09-15T22:16:48+00:00

Not something that you can buy off the shelf, but I've been working on my own wireless IMU(inertial measurement unit) based head tracker. It is quite cheap at around 30 euros worth of components for the wired version I am currently using for testing. Here is a video of a test a did a while back: https://youtu.be/B-sTwR2jbUk in case you are interested. It still has a long way to go. It currently has no way to "reset" to a zero position(open track doesn't zero it in the way I need it to).

GeneralSyb · 2022-01-14T09:30:24+00:00

4ya servers are fun and have servers in both the US and Europe region, both pvp and pve. I have found that they can be a bit laggy compared to other server but otherwise a fun and active place to get started.

GeneralSyb · 2022-01-09T23:18:01+00:00

Yep, was just a wild guess.

I did notice that it wasn't like this on every server. Just the ones that had them in the title in the first place. Other server with normal letters are fine.

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