fullsquare

u/fullsquare@awful.systems
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(Current rabbit hole: Should a HB9CV’s boom be conductive and electrically bonded to its elements?)

Yes it has to be, that's how you feed its two elements. Boom is at zero electrical potential and forms half of transmission line that goes to gamma matches of both parts of antenna, and you can attach it to perpendicular conductive mast, or extend it for mounting to mast (has to be perpendicular if mast is metal)

Personally, i'd go with 4el yagi if we're talking portable operation, because boom length is such that you can make it out of plastic tube and hide elements in it when moving around. Or moxon, if size of 4el yagi is prohibitive. Moxon gets you 2db more gain than HB9CV in similar footprint

spotted on r/betteroffline: Nscale, one of neocloud companies, released S-1. even when they show "adjusted EBITDA" and "adjusted operational loss" where they exclude, among other things, depreciation and stock based compensation, they never break even on that "adjusted operational loss", net losses are multiple hundred % (ie. they lose 4x-23x as much as they receive in revenue)

but yeah, it's profitable on inference, it's the worst it'll ever be and other marketing lies from twitter's most concussed boosters

who is "we"? as of now, there's still oil being extracted and fertilizer being produced, just a bit less of it. if you live in a western country you don't have to worry too much about it, except higher prices of food and everything that gets transported. if you're a subsistence farmer in a place like bangladesh then you're to some degree fucked

now you have it straight from source:

e/acc, distinct from EA, is a rival ideology about technology.

(somewhere in this mix someone called me e/acc. i am not. if you're going to classify me in this space, i am something like a Kurzweilian h+

e/acc is a troll ideology for upsetting EA people and scamming pmarca.)

then he complains about sneerclub for some reason, damn i can't guess why

if anyone has Rat Explainer For Normal People 101, not written by weirdos (derogatory) that would be useful i think now that what is known here for decade broke into mainstream

LLMs doing Great Things Worth Ruining The World Over in medical research

there are entire wet labs whose software stack predates openai. go and ask anyone who works in a moderately long operating lab if there's any load bearing Thing that runs under windows xp control or older (there will be). there are some extremely limited applications of pre-llm ml in drug design, but it's trained on entirely different type of data and it does entirely different thing and i'd say it's not load bearing. these things are expected to be fed with new data from testing new things provided in previous iterations and if you hit something you'll get there on your own. all of that data is noisy

openhamprep explanation is wrong

When you consider a segment of wire, it has some inductance and capacitance in that small segment, and the wider it is, the lower inductance and higher capacitance are. In other words, both X_L and X_C go down as diameter increases. Electric field lines within antenna are mostly perpendicular to wire everywhere except on ends, where they spread in all directions, which means that there's some residual capacitance there that needs to be charged each cycle. This is called end effect and the wider wire is, the more of it you get. In fact, the same aspect ratio (length/diameter) gets you the same end effect ratio each time, and it's usually in range of 0.98-0.95. If there's insulation, then insulation has lower velocity of propagation as it has higher permittivity than air, and it is in place with highest electric field intensity, and this can also shorten necessary wire length a couple %. The more insulation there is, the more shortened antenna becomes. have a calculator: https://www.translatorscafe.com/unit-converter/en-US/calculator/dipole-antenna/

But wait, there's more. We can think of antenna as a lossy RLC resonator (sort of), where R is Rrad which for halfwave dipole would be 72 ohms, + loss resistance which is smaller, and neither are changing fast with frequency. What is changing faster is X_L and X_C, and the wider wire is, the smaller both of them are (X_L = -X_C at resonance), and this means that you can go further off frequency and still have acceptable SWR, i.e. antenna made with wider wire has more bandwidth, or if we look at it as resonator, lower Q. For HF this means using masts or wire cages instead of single wire, but for VHF this gets more practical

Resistive part of antenna impedance near resonance depends on physical antenna length, and if antenna is shortened, then how it was done, but for the range we're here it won't change much. But also it will depend on height above ground, type of soil, antenna geometry and many other things. 72 ohm is in freespace only

you can consider antenna wire as a transmission line, but it will need to include ground as the other side of transmission line, and then impedance is dependent on wire diameter to height over ground ratio. it's not very useful except when considering very large and currently uncommon types of antennas (beverage antenna and rhombic antenna, both of which are traveling wave antennas). other than that, transmission line interpretation only works when antenna is very close to ground in wavelength terms, and usually it's way below what you need for radiation to work properly. when it's way up there, or in free space, there's another impedance that is specific to wire in free space only and not dependent on length, but it's not very useful for explanation of anything in antennas