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Cake day: March 31st, 2025

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  • you can’t turn a gas into liquid by compression alone if temperature is above critical point, you also need to cool it down. separation is done by fractional distillation, but the reason it’s done is mostly about oxygen (medical and steelmaking among some other uses). for nitrogen it’s somewhere about -150C. first air is stripped of water and carbon dioxide, then it’s turned into a liquid, then it’s separated into oxygen, nitrogen and argon, and some large specialized plants also separate xenon, krypton and neon

    if you don’t actually care for it being a liquid, there’s another method called pressure swing adsorption that separates gases based on how tightly do they bind to porous surfaces under pressure. this is how medical oxygen concentrators work

    making liquid nitrogen is pretty efficient these days, as in not much more energy is used than is actually needed















  • Mate do i have just the right thing for you, but it requires some soldering. It’s also probably cheapest solution working over longer range than you need

    First you need two directional antennas. Use this https://lea.hamradio.si/~s53mv/wumca/cup.html the 13cm design specifically. Design of the dipole element is on another page https://lea.hamradio.si/~s53mv/wumca/sbfa.html They’re using hard to get semirigid coax but you can really just use common RG178 with braid tinned to make it stiff. This way you don’t have to leave D section they way they did, you can just solder core to the shield at the end while preserving total length (or ~1-2 mm less, because wifi is slightly higher frequency; 53-52 mm total). That dummy cable thing can be just any stiff piece of wire. Good way to get this would be getting a pack of u.fl-SMA pigtails, which you can also use for connection.

    You also don’t need special aluminum housing like they do, cookie tin of the right size would be sufficient, or any other container of similar nature. If you can’t weatherproof it, putting it inside on windowsill is also fine

    Then, plug TL-WN722N into it, or some other single-antenna thing, and you’re set. This one connects over USB and has removable RPSMA antenna, so you can connect it easily with correct cable (SMA plug - RPSMA plug)

    to your new directional antenna. This thing works well over 200m distance, provided clear line of sight, and probably more than that