skillissuer

@skillissuer@discuss.tchncs.de

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨1⁩ ⁨day⁩ ago⁩:

  you don’t see BNC as often because it’s more expensive, bulkier, requires different crimping tool and has a separate pin. but if you need to connect and disconnect things often and quickly, then it’s a good connector. i bet you’ve seen (RP-)SMA a lot instead, but this one is also more expensive than F, has separate pin and is too small to easily make a connector for common 75 ohm cables. reducing diameter would mean higher loss

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨2⁩ ⁨days⁩ ago⁩:

  i keep hearing that F stands for Flimsy. no idea where that came from, unless something is seriously wrong with crimping technique. i guess there’s a tradeoff between CCS or copper cable with durability of pin/center conductor vs bending radius, and some people don’t like how it turns out, while ignoring that it’s cheap and not really designed for multiple disconnections

  but yeah, as long as everything is matched good-enough then it’s a cheap way to connect low loss, cheap cable

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨2⁩ ⁨days⁩ ago⁩:

  The context of the whole thread, though, was end-user, repeated, frequent connections for people who have to be reminded by a manual that the thing needs to be plugged in. Coax is horrible for that.

  so you want BNC

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨2⁩ ⁨days⁩ ago⁩:

  power plug with 3 wires or 5 wires (3-phase) could be made safe-ish if there was a button at the very end that connected to a relay or something. but plug like this would be comically long for any practical power

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨2⁩ ⁨days⁩ ago⁩:

  i don’t think you’re supposed to hotplug soldering iron tip. besides it’s a simple thing, isn’t that just two resistors - one for heating element and another for measuring temperature? hard to break that. not sure about how ipod shuffle worked or what precautions were needed

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨2⁩ ⁨days⁩ ago⁩:

  Coax has only 2 conductors and it keeps impedance constant, unlike audio jack

• ⁨Comment⁩ on ⁨What happened to cylindrical plugs?⁩ ⁨⁨2⁩ ⁨days⁩ ago⁩:

  There are two immediate problems with round USB. First one is that audio jack carries no power and it’s generally rather harmless for finals or microphone to have some contacts shorted or crossed for time when plug is inserted. USB, let’s even just 4-pin, carries power and i’m not sure how well would either of devices react to having data bus connected to +5

  The other problem is that USB is proper radiofrequency connector, unlike audio jack where anything goes. This means it has to be shielded and impedance has to be some specified value, which in practical terms means that there’s some specific ratio of metal to plastic and shape of conductors that has to be used. Barrel plugs would have way too low impedance and already bulky connector needs extra shielding which makes it even bigger

• ⁨Comment⁩ on ⁨Antenna Recommendations⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  antenna making is art of tradeoffs. there are different ones between size, cost, weight, mechanical and electrical complexity, wideband performance, radiation pattern, efficiency, and use of harmonics if any.

  for VHF and up, it only makes sense to make single band antennas because cost and size savings are tiny otherwise, but bandwidths are large and there are no reasonable autotuners. there are special cases such as 2m/70cm antennas that can do both, but that’s it. this is area of simple or folded dipoles, halos, yagis, LPDAs, helical antennas, and in bigger end of scale antenna arrays and optical-like systems like parabolic reflectors

  for HF, if you have budget and real estate for it, some of best antennas money can buy would be LPDA for entire range you’re interested in. this thing, however, for 3-30MHz range would be a giant aluminum triangle 40m wide, 50m long, weights well over a ton and needs mast and rotator because it’s directional, not to mention that it costs fortune. but on balance it can reject noise from wrong directions and is always matched

  some typical approaches are as follows:

  1. single band wire antennas. these would be halfwave dipoles in any shape (straight, inverted-v, slopers, off-center and so on), j-poles, groundplane antennas, quarterwave dipoles (requires good ground) and couple other variations. these are light, cheap, efficient, fit entire single band without gross abuse of finals, have uniform radiation pattern. but only on one band, and having multiple of them in proximity can lead to weird effects, so these are best if you’re hiking for example, but good in general

  2. principally single band wire antennas but now we also want to squeeze some other bands out of it. these are dipoles - normal or OCFDs, full wave loops in one approach and trapped dipoles in other. in first case, we exploit the fact that there are usable harmonics on some bands - 80m has 40m, 30m, 20m, 17m, 15m, 12m and 10m. 40m has 20m, 15m and 10m. 20m has 10m. but depending on type not all are always usable and higher harmonics will have narrowed usable band compared to single band case. in trapped dipole approach there’s a limit on how many traps you can put (mitigated to some degree if you make it asymmetric and put traps on one side only), and as traps work as coils, these shorten antenna which also narrows usable bandwidth but now for lower bands, opposite of the former. use of autotuner and low loss transmission line can make it work over wider bandwidth, but this only goes so far. note that some bands are narrower than others (12m, 17m, 30m, 60m) and it can be made to work for these pretty well, but less so for others (80m, 40m, 20m, 15m, 10m), but it can still work if there’s less bands on one antenna, especially if you’re not interested in entire band (like for CW-only or voice-only operators), are willing to accept some loss of power, or use tuner, or combination of some of these

  3. antennas that are by themselves not resonant at all. these are either lossy (like terminated dipole) or require tuner, sometimes purpose-built and can be narrowband when tuned (doublets, magloops) both can be reasonably compact. because match lies in tuner, these are multiband by virtue of changing tuner settings. terminated antennas have good match but also you can be dumping half of power or more in resistor. there are also ways to use mast antennas in this way, even if they are grounded (using gamma-match for example)

  4. antennas that have to be extensively electrically shortened because wavelength is huge. these are generally everything from 160m down. these are things like magloops and bespoke wire antennas with loading coils and capacitive hats and such. because these are short in comparison to wavelength, efficiency is small and bandwidth is tiny (but can fill entire band) but also require extensive space just due to how huge wavelength is

  5. some directivity can be achieved by making yagis (higher part of HF) or by deploying multiple antennas in an array. depending on band and type of antennas this can get very elaborate and expensive. simplest and cheapest way uses multiple radiating halfwave elements connected by coils, or with parallel parasitic elements. this can get decently directional while also being a bit compact but also this makes it more narrowband and due to large size only makes sense for higher HF and VHF

  but start simple. single band wire dipole or j-pole would be probably best in your situation

• ⁨Comment⁩ on ⁨smort⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  he really said that nytimes.com/…/the-science-of-secondguessing.html

• ⁨Comment⁩ on ⁨smort⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  People who boast about their IQ are losers ~Stephen Hawking

• ⁨Comment⁩ on ⁨Antenna Recommendations⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  you might have problems with your EFHW being too lossy/undersized. check if ferrite heats up when transmitting

• ⁨Comment⁩ on ⁨Antenna Recommendations⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  you’re looking for 2 or 3, possibly more, separate antennas. consider: a groundplane, sleeve dipole, copper cactus, halo antenna or small yagi (2-3 el) for 2m; you might get away with operating them on temporary stand, or even from inside apartment. groundplane for 10m (can be made from wire; 10m is wide and you want separate, single band dipole for this reason); and some kind of wire antenna for 20m, maybe also for 10m. depending on conditions one or another might be better (vertical vs horizontal polarization, height above ground etc).

  one way to make the latter is OCFD, this way you can make antenna for both 10m and 20m; for this one you’d need some matching scheme based on specific feedpoint position, specific coax lengths (5m is halfwave at 10m so won’t change impedance at this band, but can be used to match 20m) or 1:4 or some other balun. see there for more info you can also try a full-wave loop for 20m if you have enough space, it’ll work for 10m as well. same applies for matching, that is, if you don’t have autotuner (but where’s fun in that?)

  these commercial antennas are expensive, you can have another radio for this kind of money

• ⁨Comment⁩ on ⁨Elon's understanding of science.⁩ ⁨⁨4⁩ ⁨weeks⁩ ago⁩:

  that’s just regular fox news chart

• ⁨Comment⁩ on ⁨Looking for the spelling / translation on a certain Polish word⁩ ⁨⁨4⁩ ⁨weeks⁩ ago⁩:

  This only works well for fast things tho

• ⁨Comment⁩ on ⁨Looking for the spelling / translation on a certain Polish word⁩ ⁨⁨4⁩ ⁨weeks⁩ ago⁩:

  the word you’re looking for is “jedzie”

  strictly speaking polish (and all slavic languages i think?) doesn’t have a verb like “go”. you have to specify, you can ride, drive, walk, sail, swim, roll and so on but you can’t “go”. that verb (which means “[there it] drives”) would be usually used for land vehicles, for boats we’d use “płynie” (“swim”, “sail”, “flow” depending on context)

• ⁨Comment⁩ on ⁨Why do so many UK electrical sockets have an on/off switch next to them?⁩ ⁨⁨5⁩ ⁨weeks⁩ ago⁩:

  i understand that it’s remnant from times when fusebox wasn’t a thing and it was an attempt at protecting ring circuit, that’s all. it makes little sense

• ⁨Comment⁩ on ⁨Why do so many UK electrical sockets have an on/off switch next to them?⁩ ⁨⁨5⁩ ⁨weeks⁩ ago⁩:

  fuse is in plug and accessible only when plug is disconnected

  it’s also a very weird thing because fuses are supposed to protect what is downstream of them. so effectively fuse in plug protects cord and appliance only, not the wires in the wall. there’s breaker box for this

• ⁨Comment⁩ on ⁨Why do so many UK electrical sockets have an on/off switch next to them?⁩ ⁨⁨5⁩ ⁨weeks⁩ ago⁩:

  eastern block solution to copper shortages was to wire houses with aluminum instead of copper. this avoided all that bizarre bullshit that brits do, and in principle it’s a good idea since aluminum is used for big time power distribution as well. this worked pretty well until it was noticed that under some conditions hot spots can form on connections over time, requiring replacement of connectors. it’s still legal to use aluminum wires in some places, but copper is more common now

• ⁨Comment⁩ on ⁨Why do so many UK electrical sockets have an on/off switch next to them?⁩ ⁨⁨5⁩ ⁨weeks⁩ ago⁩:

  at least in part it’s an end result of decades of crud and tech debt, so to speak, accumulating in british power grid and home wiring. they do it this way because otherwise it won’t be safe. continental euro home wiring usually has thicker wires, residual-current circuit breakers and no ring circuits so we get away without fuzes and switches. sometimes we do have ring circuits kind of thing, but not in house wiring, instead it’s in medium voltage distribution grid, and it’s sized so that it can serve most of loads after single failure.

  explanation

  in normal state, medium voltage line (like 15kV, 20kV) might branch out in rural terrain from substation to two or more places. in case of single failure, mildly common after storms, everything downstream would be down. instead, to increase reliability, every few km there’s a switch and some of the far ends have line between them that is usually disconnected. in case of single failure, damaged segment is cut off, and the far end of the loop switch gets closed. this way power is delivered the long way around the loop, allowing for repairs of the damaged sector in the meantime. this also specifically avoids some of problems of ring circuits especially in situation when some lines might be damaged.

• ⁨Comment⁩ on ⁨What is the most toxic instance of Lemmy?⁩ ⁨⁨5⁩ ⁨weeks⁩ ago⁩:

  they are remnants of explodingheads that stayed on lemmy, so you’re spot on

• ⁨Comment⁩ on ⁨A totally normal figure of cancer signaling pathways⁩ ⁨⁨1⁩ ⁨month⁩ ago⁩:

  It’s still up, just remove trailing dot from DOI

• ⁨Comment⁩ on ⁨What's Rednote and why is "everyone" talking about it?⁩ ⁨⁨1⁩ ⁨month⁩ ago⁩:

  instagram/pinterest-ish chinese app that was promoted on american tiktok as a possible alternative after ban. it has actual chinese users and they weren’t impressed when american transplants wanted everyone to speak english

  Image

• ⁨Comment⁩ on ⁨A totally normal figure of cancer signaling pathways⁩ ⁨⁨1⁩ ⁨month⁩ ago⁩:

  text looks sus too

• ⁨Comment⁩ on ⁨diy qfh antenna⁩ ⁨⁨1⁩ ⁨month⁩ ago⁩:

  now that i’m thinking, you can make loop antenna with circular polarization and mesh reflector with closer spacing that would be even more compact and that would have more of one sided donut shaped radiation pattern, which would be probably more suitable for your application, but it’s guaranteed to have different impedance and so would require simulation

• ⁨Comment⁩ on ⁨diy qfh antenna⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  wait, do you want to use it at 140-ish MHz? these antennas will be quite sizable no matter what you do. you can make cross-dipole yagi but with loops instead of straight elements to make it a bit more compact. again, one director will be fine. take reflector + driven element from there www.robkalmeijer.nl/techniek/…/index.html and first director from there iw5edi.com/…/directional-antennas-cubical-quad this will get you antenna looking roughly like a cube with 50cm side. i don’t think you can get much more compact

• ⁨Comment⁩ on ⁨diy qfh antenna⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  wood is fine but make sure to waterproof it if used outside. use as little as practical, performance can change with weather unlike with plastic. no metal fasteners either as this will have weird effects

  do you want it to be compact when deployed or compact when stored? you can also make crossed dipole yagi, you probably want it to be rather nondirectional so one director, driven element and reflector would be fine. that antenna is much longer but i think you get the idea www.qsl.net/dk7zb/Cross-Yagi/crossyagi.htm you can also make bifiliar helical antenna but this one again gets a bit directional. you can probably make it shorter than these 5 turns and change pitch too to decrease directionality secwww.jhuapl.edu/…/12-01-Stilwell.pdf you can also make unifilar helical antenna but it needs a big reflector baseplate so it won’t be as compact, it looks like this www.ab9il.net/wlan-projects/wifi3A.html

• ⁨Comment⁩ on ⁨Biblically Accurate Reactor⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  if it’s too heat sensitive to distill then vacuum distillation is an option, but size of batch won’t matter too hard

  if it really can’t be done, then there are ways to make it work without distillation

• ⁨Comment⁩ on ⁨Biblically Accurate Reactor⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  gotta be some kind of air-free electrochemical setup, i agree

• ⁨Comment⁩ on ⁨Why do people say things like "I didn't do nothing"?⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  more common than you think en.wikipedia.org/wiki/Double_negative

  different dialects can have different rules about their use

• ⁨Comment⁩ on ⁨Looking for answers⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  Pacifism is only good for aggressors and cowards