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fullsquare

@ fullsquare @awful.systems

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338
Joined
1 yr. ago

  • Ukraine Is Jamming Russia’s ‘Superweapon’ With a Song

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  • plenty of drone teams release geolocated videos day after they happen, but in this case i'll guess that real sauce is classified top secret, that thing is outdated info and everyone is five steps ahead

    ahem

    triple the defense budget

  • Ukraine Is Jamming Russia’s ‘Superweapon’ With a Song

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  • the theoretical reason for doing that is that if you have to split jamming power over broader frequency range, then for every n^2 times increase in bandwidth, here number of channels, range decreases n times. however gnss signals are so weak, it probably doesn't matter, and if you're adding extra power per channel, then it doesn't apply

    now if missile detects that gnss is fucked with (signal too strong, wrong direction, physically impossible location), the correct thing to do would be to fallback to inertial navigation while accepting that accuracy decreases until gnss can be received again, if at all, and acted upon. theoretically speaking, it's a matter of software update, better hardware also can help with that, so idk why would they release this. maybe there's something that prevents this

  • Why aren't you on #NOSTR

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  • because it's packed with nazis and cryptobros with their spam. moderation is very limited by design

  • Deleted

    Permanently Deleted

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  • this is how 238Pu ceramic pellets for space probe generators look like, no fission required just alpha decay. If it was fission, it wouldn't need to glow like this entire time because you can just turn it off

  • Whats your hot take on something that doesnt matter at all?

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  • here if you need anything over certain power (6kW; depends on country i guess) you need a three phase installation, and even if you get single phase, it's really handled as three phase split between single phase customers (a block gets three phase supply, then splits flats in three groups, each group gets connected to one phase). this gets supplied by a distribution transformer that might serve somewhere around 200 people per (in residential areas)

    i understand that sometimes americans also get distribution like this, with 208/120 three phase coming from substation, without 240v available

  • Whats your hot take on something that doesnt matter at all?

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  • american version would probably only have two phases at best, and possibly just one

  • Whats your hot take on something that doesnt matter at all?

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  • wait, how do you route cables in there? is there just a massive bundle right through the middle?

  • How secure is Lemmy/federated services from datamining?

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  • ye except that depending on how paranoid are you this also means that all personal/small instances will be always suspicious and most of popular instances allow lots of that by default

  • How secure is Lemmy/federated services from datamining?

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  • Absolutely none, and it's by design. All you need to do is setup an instance and everything you might need gets right into database

  • Radio wizards and witches, what is the deal with antenna for the ~7 MHz amateur band?

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  • if you have an antenna with impedance of, say, 200 ohms, then you need to match it to transmitter impedance of 50 ohms, or else most of power output from transmitter would be bounced back and will damage output stage of amplifier. because on receive currents are tiny, you can wing it by just using it without any match and connecting it directly

  • Radio wizards and witches, what is the deal with antenna for the ~7 MHz amateur band?

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  • transformers are not the only way to do this, and some other circuits can be used instead. if you take a transformer with 1:2 winding ratio, then if on one side current is 1 and voltage is 1, then on the other current will be 0.5 and voltage 2, which means that impedance increases 4x. in EFHW, it's 1:7 winding ratio and impedance ratio is 49x, which works for end-feeding a half-wave dipole, just as expected (from 50 ohm to ~2500 ohm). that transformer is a limitation on power usable in this antenna and main reason to use this type of antenna is mechanical

    most importantly, transformers work nicely only if you have real impedances, so your antenna has to be resonant anyway. l- or pi-network tuner will also handle complex impedances so doublet or random wire will work nicely with it, as long as you can accept weight and losses in tuner

  • Radio wizards and witches, what is the deal with antenna for the ~7 MHz amateur band?

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  • how compact and what do you want to do with it? if it's for receive only, the most compact you can get is ferrite rod antenna, but it's very different from usual wire antennas used for transmission. if using wire antennas, random wire would be fine

  • Radio wizards and witches, what is the deal with antenna for the ~7 MHz amateur band?

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  • it depends on whether you want to transmit or not. if not, you can just use random wire antenna

    random wire antenna is exactly what it says on the tin - length of random wire strung up as high as you can, as long as you can make it work. the other part is ground, where you might want to lay some lengths of wire and connect them in a single point, to act as radio ground. it won't have right impedance (probably 50 ohm) but for receive, this is ok - it'll be probably usable, and you can amplify signal without penalty because amplifier noise will be much smaller than atmospheric noise already present. the amount of power bouncing around is tiny and can't damage anything

    if you want to transmit, you'll need more elaborate antenna. what you can use depends on whether do you have a tuner like neidu3 describes or not. if you do, common choice is doublet which is a specific length of wire connected to tuner with a 400-ohm parallel line. if you don't, common choice is halfwave dipole which is halfwave long, and put as high as you can get, either vertical or horizontal, but for practical reasons mostly horizontal, or monopole, that is quarterwave long, but requires lots of wire on ground to act as radio ground. you can make them shorter using coils, but this makes bandwidth narrower. in any case, it'll be need to be tuned to your band in question, for which you need a tool like nanoVNA. tuner also narrows your bandwidth, but you can retune it so it doesn't matter that much. (it'c called instantaneous bandwidth)

  • Trump Administration Providing Weapons Grade Plutonium to Sam Altman

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  • Utter nonsense

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  • i don't mean beta-oxidation, it's just a series of separated normal reactions. i mean something like this: when first learning about ketones, you might learn about aldol condensation, which has enol as a nucleophile and another carbonyl as electrophile. at some other point you might learn about strecker reaction, which has iminium ion as electrophile and cyanide as nucleophile. but really, what you can do is mix and match, and you can pair enolizable ketone and iminium (mannich reaction) or carbonyl and cyanide (cyanohydrin formation) and then generalize, for example you don't need strictly ketone for mannich, you can use any electron rich conjugated system like malonate or nitroalkane anion (henry reaction) or phenol or indole. to figure this out you need to study mechanisms. these last two are usually treated as variants of friedel-crafts reaction, but really categories like this are fake

    and to get that right, you need to know how these reactive intermediates look like, how reactive they are, what influences their stability which means that ochem starts with discussion of carbocations, carboanions, radicals, their shapes and orbitals involved, hyperconjugation, solvent effects and the like. and then first reactions taught are sn1/sn2, because these showcase these fundamentals nicely, and from there, it's about introduction of more compound classes

    we only had synthons introduced during lecture at around 4th year, and only for ochem path, it's not doing a lot at that point and imo would have much more impact right after ochem intro course

  • Utter nonsense

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  • Utter nonsense

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  • i'd say it's more important to learn mechanisms because this way you can notice these patterns of reactivity easier. at some point you'd only get new reactions that are really just pieces of other reactions you know put in a new way

  • Utter nonsense

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  • there's zero reason to make chart like this, it's both barely comprehensible and touching surface level stuff only (where are palladium couplings for one)

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    What do you think about Russia and America testing their nuclear arms yesterday?

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  • is there something you don't understand? it doesn't fucking matter what russians claim to have tested, you as nato resident are protected by nato's ability to evaporate moscow and moscow residents survival instinct, meaning that they won't start shit if they want to remain not evaporated. it works in any number of ways between any number of nuclear states, and can't be undone