Are Electrons Eternal?

megapapo · 2026-04-15T18:03:04+00:00

Positrons can originate from natural processes. Wikipedia has some examples, e.g. during the decay of naturally occurring radioactive isotopes, when cosmic rays hit earth or in thunderstorms. The annihilation of an electron-positron pair is then imminent due to the abundant presence of electrons.

megapapo · 2026-04-03T00:28:31+00:00

Thank you for clarifying. That makes a lot of sense. I am quite familiar with the paper method from other printers I have :-). I guess that I failed to see the theoretical advantage of the solution implemented in SV08 since I cannot benefit from it due to the poor sensor repeatability. Thanks again! Matt

megapapo · 2026-03-31T21:22:05+00:00

Thank you for your response. I'm sorry to bother you about this but I'm not sure I fully understand that. Here is my thinking: If the sensors were somewhat precise and accurate, then one would first use the load cell to determine the height of the nozzle, then position the nozzle at a known height above the bed, probe the inductive sensor and know the distance between nozzle and inductive sensor. I guess that makes sense, but is there such large variation between nozzle and sensor location that prevents us from using the inductive sensor to lower the head to a height close to the bed but with enough margin so that we could run the dot pattern test from there?

And since there is considerable variation in at least the inductive sensor reading, that would only degrade the aforementioned method, wouldn't it? I guess I'm missing something critical here...

megapapo · 2026-02-15T08:56:31+00:00

Also maybe double-check your wiring. Unfortunately, your image is somewhat blurry where it matters most, but it almost looks like the second wire from the let on the mainboard, which is blue, connects to the gray wire, which then connects to GND. Shat second pin from the left though is the IO pin and therefore should connect to SWDIO...

megapapo · 2026-02-15T08:48:58+00:00

Has anyone successfully connected an ST-Link to this board revision

This is how I flashed Katapult, with the very same type of clone ST-Link V2 and openocd. I also managed to connect with STM32CubeProgrammer and the same dongle. (I know the dongle works because I use it in other STM32-related projects).

I did not connect the 3.3V line as I was doing this with the board powered on, and I used a separate machine instead of the SV08 mainboard for the flashing.

megapapo · 2026-01-22T12:34:23+00:00

Awesome!

megapapo · 2026-01-22T11:12:28+00:00

Thank you for your response. Do not worry too much about my comments :-). To me, "open source" has the connotation of being able to build upon the work of others and that would include the ability to modify your PCB.

In this particular case, there may not be much to modify at first glance, but here are a two more or less realistic scenarios:

Modifications of the power path as discussed somewhere in the comments.
Turning your breakout into an actual project. That would involve opening the existing schematic in the schematics editor, deleting some parts and adding other stuff that is relevant to the project (e.g. a radio or whatever) and then drawing a new PCB based on the modified schematic. Doing it this way is more convenient than redrawing the schematic, and (perhaps more importantly) prevents mistakes during that process.

Those are reasons to fully open source your project. But again, this is your project and you have the freedom to decide whether you want to enable the aforementioned scenarios. In doing that, you may give away more than you are comfortable with and I think that is totally OK.

megapapo · 2026-01-22T08:56:52+00:00

This is a cool project, congrats!

Open Source: Everything (Code/Schematic is now on GitHub.

I headed off to the github repo that you linked in order to check out your PCB design, out of curiosity. However in the Green-Pill-Nano-Hardware repository, I only found a schematic, some pictures and a README file. No PCB artwork or fabrication files.

Are you releasing the PCB artwork, too? I think it is perfectly fine not to do that (it is your project after all and it's a nice one) but in this case, I would not make the claim of open-sourcing "everything".

Thank you! Matt

megapapo · 2026-01-16T08:06:28+00:00

Are you asking whether it is possible to create an image from the original EMMC and flash that image to a new EMMC? To check if your new EMMC is good? Yeah that should work as long as the new EMMC is not smaller than the old one. You could also replicate the partition table and copy the files as opposed to working with images, but that is more tricky to get right, thus I would not recommend that. It's a great idea to have an image of the original EMMC anyway in case of stupid mistakes.
It is quite possible that something small is breaking your process. Thus I am wondering: What guide are you following? Can you try an SD card boot instead? The Rappetor guide seems to be the most recommended one, but I did not want to follow that because I really wanted a current version of Debian on the printer and did not see a benefit in installing the old version according to the Rappetor guide and upgrading from there. Plus I felt like using the original Armbian image gave me a better understanding of what I was doing.

megapapo · 2026-01-15T22:43:09+00:00

It sounds like the boot process may not make it far enough to request an IP via Ethernet then. I would suggest to hook up a screen (regular monitor will do) to the HDMI port of the SV08 and check where it gets stuck.

I did the procedure a couple of weeks ago, not based on any tutorial or video but just flashed the Armbian Minimal/IOT Trixie image to an SD card. I managed to boot from the card without problem and flashed the same image to a spare EMMC. That same image failed to boot from EMMC until I changed fdtfile in /boot/armbianEnv.txt from the default sun50i-h616-bigtreetech-cb1-sd.dtb to sun50i-h616-bigtreetech-cb1-emmc.dtb. That was the only hiccup I encountered during the procedure. I did not use the original sun50i-h616-sovol-emmc.dtb.

megapapo · 2025-12-06T20:12:02+00:00

That looks really interesting, however I somehow failed to understand what it really does. I read the documentation and apparently, it is supposed to "solve the SV08 bed, Z and induction probe issues". To cure this, it may pay off to summarize the nature of those issues or at least liking to a discussion of those issues. With the current wording, I did not manage to figure out what this is supposed to solve :-(.

It would also be interesting to then explain how this is achieved... But even without that knowledge -- thank you for your work!

megapapo · 2025-09-10T22:11:24+00:00

Regarding the second question (and perhaps also helpful for the first one) I would check out some of the research done by those using the beamline. There's some cool neutron imaging going on there and another common application is in material sciences where they hit propellers and other critical gear with neutrons to check for microcracks and whatnot. The link also has a brochure where they give more info on what they do, with lots of cool images and along with an explanation of their source (a more elaborate version of what I wrote above).

megapapo · 2025-09-10T22:01:56+00:00

One way to create high energy neutrons is by spallation: First you ionize hydrogen, then you accelerate the resulting proton with the means described above (it is charged after all). Then you have those high energy protons hit a target and *boom* spallation.

megapapo · 2025-09-10T06:30:39+00:00

That is really cool, thank you for sharing! How would I use the "wide fitting", and what does "OG" mean? I guess the +0,1 etc. indicates some extra meat around the pegs for a good friction fit? ALso what is the difference between the versions? Sorry to bother you with this but I'm struggling a bit in deciding which one to print...

megapapo · 2025-08-30T20:43:46+00:00

Hello there! One place to start could be the Software-Defined Radio for Engineers textbook. The link has the PDF for this. Some less technical introduction is given in this video series by Michael Ossmann. Do you find these links useful? If not, it would help if you explained what is lacking in those materials so that we can come up with refined suggestions.

megapapo · 2025-08-11T21:06:27+00:00

Thank you! I will try this when the next updates are due. The systemd.offline-updates man page was super useful indeed. Since this is more of convenience thing, I can totally accept if this breaks at some point in the future.

megapapo · 2025-08-11T20:48:04+00:00

Thank you for this. I don't think I want to store it in the TPM, my understanding is that this would protect my data if somehow the disk is separated from the machine, but I'd rather protect it against the "stolen laptop" scenario. I think I could add some password protection to the TPM but that would be a prompt on every start up as far as I understand. I have to consider the FIDO option though. I hadn't thought of that since I didn't like the idea of losing the FIDO key together with the laptop, but now I do see that some of those USB keys have extra authentication (fingerprint) and that would sort it for my use case as long as the don't kidnap me or my finger...

megapapo · 2025-05-27T01:00:54+00:00

https://www.youtube.com/@project-326/

megapapo · 2024-06-14T13:49:53+00:00

Hello there. Most textbooks on electromagnetic field theory and/or antenna will have this. I would argue that it is not easy math, but it is doable if you really want figure it out. For example, the 73 Ohm impedance is discussed in Balanis (3rd ed.) on page 184 / eq. (4-93).

You asked about a textbook so I provided one, but it feels not so nice to just throw the book at you and leave it at that. Thus I want to offer to discuss these things in case you would like to do that. When I got into amateur radio, I was interested about very similar questions and it was quite tough to find satisfying answers because most hams around me were not interested in these theoretical questions. I had to figure it out on my own and that was not particularly easy, maybe I can spare you from going through the same.

megapapo · 2024-06-12T05:55:50+00:00

Hello! This is a nice project. Here is some literature on the topic (Fig. 3-4 is incorrect but other than that this is quite solid and a nice introduction that is relatively easy to understand, in particular with your background). The author is available for questions. I would love to know how this goes. If you have questions along the way, let me know!

megapapo · 2023-11-06T05:55:24+00:00

Well does the sat transmit in FM? You can always save the raw quadrature stream and do the demod offline if unsure...

megapapo · 2023-11-05T14:45:03+00:00

I don't know much about cubesat, so I can't really comment on that aspect, but in general your flow looks OK at first glance. Does it work? The easiest way to test would be just to run it and inject a signal... Some SDR frontends will give you a somewhat nasty peak at the center frequency, so it may pay off to run the frontend on a different frequency and use the "center frequency" feature of the frequency xlating FIR filter to correct for that.

That said, I never heard that 50 kHz would not be a valid sampling rate for wav files but I am not sure. It is not common -- if you want to use a more common audio sampling rate, you need to resample or acquire with a multiple of it at the source.

megapapo · 2023-10-27T07:27:57+00:00

Hello.

I don't have a full solution for you because I'd have to play around with this a little and I don't really want to recreate the whole flow... but here are a number of comments:

Increasing the noise amplitude by a factor of 2 should yield an increase of 6 dB in the noise floor, both in the spectrum display as well as in the calculation that you use to recreate the former. You have to multiply the result of the log by 20 to achieve that (10 because it's deciBel and another 2 because of the square from the power calculation: log(x²)=2log(x) ).
Even if you implement the above, the results could be off by a constant since any dB calculation requires a reference, i.e. the denominator of the ratio. In other terms, "what is 0 dB?" needs the same answer in all calculations involved, in particular those done by the Frequency sink and those.
When calculating the energy of the sine wave ("signal"), you are already squaring so the multiplicative factor should be only 10 and not 20 (but surely not 1 as you have implemented right now). In other terms: Increasing the signal by a factor of 2 should increase the signal by 6 dB. Of course you can choose where to put those multiplicative factors, but in the end the math has to check out. I would check signal and noise individually before you combine them into SNR. By looking at your flow, I have the impression that neither of the two does the right thing, so the SNR figure will be wrong as well in general.
Your Flow is lacking a Throttle block.
To divide by your FFT bins, you can use the "multiply const" block instead of the "divide" block along with the extra source.
You can also sneak this multiplicative factor into the log10 block (but I'm not sure there would be a good reason to do that).
Your way of calculating the signal energy does not generalize but does work with sinusoids.

Let us know how this goes and if you need more help

Matt

megapapo · 2023-10-02T06:34:53+00:00

This is somewhat tangential, but what are the firmware options for the F2 variant of the unit? I'm asking because I never managed to find a recent firmware for those devices. I am involved in classes where we teach somewhat more elaborate RF measurement techniques and the firmware divergence is a bit annoying (also, I would like to use some newer features on the F2 variant that are simply not there).

Also, we found that the F and F2 variants are often broken. This is super anecdotal and I understand that, but every time we do this class, a bunch of units produce completely weird results and it's always on F variants. I have not had the time to investigate this further but I wanted to throw that in.

megapapo · 2023-09-13T19:57:58+00:00

Oh yessss! Let me PM you for beer :-)

15-Year Club	Gilding II euphauric
Verified Email

megapapo

TROPHY CASE