fullsquare
@fullsquare@awful.systems
- Comment on This figure illustration from an article on AI sycophancy and human behavior is the epitome of 2026 1 week ago:
there was a time when anthropic models would refuse any question related to medicine. not because they care that hard, mind you. it’s because that bloated startup is ran by cultists and they were worried that chatbot will come up with a bioweapon
- Comment on All mixed up 2 weeks ago:
if you do that you have bigger problems
- Comment on All mixed up 3 weeks ago:
only if you take notes
- Comment on All mixed up 3 weeks ago:
this advice is specifically about sulfuric acid. it’s denser than water, so if added to it it will sink diluting itself along the way, while also heating water around and making it float to the surface. if done opposite way, water won’t mix immediately because of large density difference so neutralizatio heat will be deposited on surface between these two boiling water and throwing acid around. this matters less with other acids because less heat is deposited, and in some cases acid is less dense than water. but if you stir the acid quickly, you can do it either way as long as you control temperature. this also is the case when you need to mix two different acids
tldr you can do whatever you want as long as you know what are you doing
- Comment on Science is iterative 3 weeks ago:
technically pv panels are also heat engines. this is why they need cooling
- Comment on Science is iterative 3 weeks ago:
the steam part is in the rest of hydrological cycle
- Comment on load bearing worm 5 weeks ago:
seeing that jargon file has an extensive page on retrocomputing feels like figuring out that there were archeologists in ancient egypt
- Comment on load bearing worm 5 weeks ago:
some people would tell you that we can simulate small bits of chemistry but it’s flat out wrong (i might be biased as i’ve wrangled for a year with computational chemists about results that don’t conform to reality) and even then errors are so large that’s it’s useless
- Comment on what is this??? 5 weeks ago:
Pain
- Comment on load bearing worm 5 weeks ago:
and then some bozo says that biology is just complicated chemistry and chemistry is just complicated physics and we can simulate physics
curious thing is that i never hear biologists or chemists saying that, only some physicists and techbros. just trying to simulate your way out of small organic chemistry problems will make you even more hopelessly lost than you were before
- Comment on load bearing worm 5 weeks ago:
maybe it introduces some critical contaminant (many such cases)
- Comment on Wonder why? 5 weeks ago:
that’s a weird metric to look at because drug approval happens only like, 5-15 years after end of preclinical research, sometimes longer
- Comment on За що дають тіньовий Бан на reddit? 5 weeks ago:
Shadowban is when you can see your own post/comment but it’s unsearchable or otherwise unreachable by other people. milder variant is comments hidden by default, some of them look like deleted by mod but it might be automatic. this is something different, why it happened to you idk but there is some trade in old accounts for spam purposes, maybe that’s why
- Comment on Who's receiving and who's loosing electrons? 1 month ago:
there is empirical series of materials sorted from which one is most likely to lose vs gain electrons, but what exactly happens is one of unsolved problems in physics
- Comment on why does almost nobody live here? 1 month ago:
i think that when locals call a place “the land that god made in anger”, it might be wise to not settle there
- Comment on Radioactive Steel 1 month ago:
they did a whoopsie, lead 210 comes from uranium 238. every 220 years radioactivity drops 1000x which means that 200-300 year old lead is mostly fine. copper notably doesn’t have this problem, is dense and is refined to high degree, at scale. it’s good enough to shield most of relatively low energy radiation from that isotope (less than 50kev gammas). couple mm of copper should be plenty for many applications
- Comment on Gotta go fast 1 month ago:
different tool for a different purpose. water has a large heat of evaporation which is something that allows for more compact turbines
- Comment on Gotta go fast 1 month ago:
big advantage is that molten salt allows for energy storage for nighttime
- Comment on Can studying Marxism and such help you become better at writing without AI? Just asking. 1 month ago:
lol this is a question that could only be asked on lemmy. read what you want but more importantly practice
- Comment on Linux Ham Radio KISS Serial Driver Being Modernized In 2026 1 month ago:
dropped as cleanup-only, not allowed by their policies
i suspect that it might be vibecoded, too
- Comment on po-tay-toes 2 months ago:
it also happened with tramadol before (different plant)
- Comment on That's how the world works. 2 months ago:
Adding to that, logistics are such that direct impact will be felt strongest in places like India that rely heavily on Qatari LNG to make fertilizer, but many places have other sources of both gas and fertilizer. Americas, EU, Russia and China will get by because they have their own supply and will be only affected by price increase
- Comment on That's how the world works. 2 months ago:
without synthetic nitrogen fertilizer there’s only enough reactive nitrogen going around for something like 1-1.5B people. yea mate very sustainable to retvrn to traditional farming and starve 80% of the planet in the process
- Comment on What is a good Matrix (public) home server besides the big matrix.org one? 2 months ago:
join some matrix room that you like and look around for people’s homeservers
- Comment on 3D printed motorized variable capacitor, butterfly-trombone hybrid (also question on dielectric losses in capacitors) 3 months ago:
i was thinking more like, thin external plastic shell and empty cells inside, perhaps with another thin plastic shell on inside, and internal metal shell (on plastic support?) fitting in snugly, for mechanical stability, idk 3dprinting
keeping leads short and nonmagnetic (dramatic reduction in skin layer depth) would be a good thing because of losses, but the longest object in capacitor would be just capacitor plates, and either way in wavelength terms it’s rather small. more precisely you can model it as open transmission line stub with some weird and low impedance, but it’s so small that you don’t have to
- Comment on Testing a shortened OCFD 3 months ago:
Found a piece about RFI and baluns, audiosystemsgroup.com/RFI-Ham.pdf multiple turns on ferrite aren’t really an option for VHF and up, ended up ordering extra beads (non-split)
- Comment on 3D printed motorized variable capacitor, butterfly-trombone hybrid (also question on dielectric losses in capacitors) 3 months ago:
The dielectric between the plates in this case is 0.4mm of ABS plastics (+ a bit of air in the 3d print layer lines).
in terms of losses, PP or PE is a bit better than ABS, teflon or FEP is a bit better than PP, but air is superior to either (this is part of the reason why foam coax is a thing). not sure which ones are printable, or whether it’s practical at this size, but try to introduce as many voids as possible (perhaps requires larger thickness of dielectric). it doesn’t matter much in your case, because of low power (warping of plastic because of excessive heat is probably not a problem). if your coax has solid dielectric, then by introducing enough air in 3d-print your variable might become less lossy than that
The Capacitors allows my 80cm diameter loop to tune from 20Mhz to 37Mhz. Sweeping the whole range is a bit slow due to the low RPM of the motor and takes about 6min. But that is kinda nice when fine adjusting to a frequency.
you have probably noticed that position vs resonant frequency relationship is rather nonlinear. you can get higher sweep speeds at lower end without losing much accuracy at higher end by tapering end of side plates into a triangle shape (it will get longer overall). it doesn’t matter much in your case, because it’s all approx monoband, but if you want to go multiband with this, then it’ll be a nice enhancement. similar effect happens when air variable capacitors have moving plates shaped in such a way that one end is longer than the other, and external edge has shape roughly like a section of logarithmic spiral. precise movement of variables like this is done by use of worm drive with large wheel
I am not sure what is causing this, but i assume it could be due to increase of dielectric losses in the capacitor getting bigger when more of the plates overlap because then the electric field has to flow thru a bigger area of dielectric, increasing the potential for losses.
loss tangent of dielectric is material property, that is ratio of equivalent loss resistance to capacitance should remain constant at given frequency. so i guess that losses should remain roughly the same, if dielectric is to blame, but at any rate lossy capacitor should make bandwidth broader and SWR lower. my guess would be that it’s a matter of coupling loop becoming wrong-sized or wrong-positioned at some point with change in frequency (try moving it up or down? there’s gotta be some optimum position for your entire range of interest)
- Submitted 3 months ago to amateur_radio@lemmy.radio | 1 comment
- Comment on Series coax stub capacitors for more precise loop antenna tuning 3 months ago:
Skin depth is larger in aluminum but not enough to balance out its lower conductivity, copper is better material taking all into account, in practice both are good. If opposite was true we’d use lead or zinc for conductors. There are satellite microwave parts made out of aluminium (low weight) coated sequentially with zinc (bonding layer), copper (better conductivity), thin layer of silver (even better conductivity) and then gold (actually not thick enough to contribute, this one is for corrosion protection)
- Comment on Series coax stub capacitors for more precise loop antenna tuning 3 months ago:
the thing with using aluminum tape is that you can get away with very small thickness, because current flows only in top tens of micrometers depending on band. you can just roll up, say, 5cm wide, 0.5mm thick aluminum tape and have riveted or maybe brazed short length of 2mm thick bar to the ends for connecting capacitor. the problem is with mechanical stability of this setup, which is why you see pipes and thicker bars, bicycle rims etc
with braid you get a lot of contacts between wires, and i’m not sure that resistance of them would be low unless tire is fully inflated. maybe you can put short U-turn within loop at end opposite of capacitor and have adjustable shorting bar there. adjustable capacitor is more common by far, because if you can adjust it widely enough, you can get to different bands