have you calibrated your nanovna? you have to do that after every change of frequency range. you need S11 smith chart, not S21 smith chart (port 2 is not connected). swr and logmag get you the same info in different formats, pick 1

1m away from metal things should be okayish but the more the better. these lights will interfere, if you could at least move them away from the corner it would be an improvement. twin lead cannot be close to metal either (is that sheet metal near bottom of antenna?) needs at least couple cm of distance from it. i would also replace that nail with a ziptie

strictly speaking that’s a slim jim. why does it have a twist in the middle? untwist it, the radiating part (upper approx 1m) should be a smooth transmission line for it to work right (or shorted at both ends)

If you want to preserve the way it’s made, you’d need to resolder the top bar after adjustment. But you also can leave wires on top unconnected

there’s been a wave of spam posts on writefreely couple of days back not sure if there’s a relation

Hey, gotta pump up these self-citation numbers somehow

the man who decided to end german nuclear power production getting a seat in gazprom doesn’t inspire confidence in reality-based discussion of this subject

they also last decades and are cheap to run with extremely low carbon emissions

most of costs are costs of construction. french and koreans don’t seem discouraged and some plants in japan and china were built under budget. finland energy supply has large fraction of nuclear and they have extremely cheap electricity

Terrorist adoption of AI has thus advanced further and more systematically than prior analysis has recognized

salafi extremists that declared western education sinful are now world-leading AI-first village-burning-as-a-service jihadist startup. okay whatever

It has aided in attack planning, weapons troubleshooting, and the design of explosive devices, as users have successfully circumvented some safeguards.

surely their contacts within ISIS or any number of other islamic militias couldn’t have taught them that previously, no they have to rely on movie plot ideas from chatbots. it probably helps that some people heard about them but peak years of their activity were in 2014-20 before ISWAP eaten their support base whole by not raiding villages and trying to replace state instead

also, when trying to make sure that i got this right i’ve learned that apparently al-qaeda pivoted to app development

i thought that pause ai was just rationalist controlled opposition

oops all Brassica

welcome to the abyss, it sucks here

That’s just the legal limit, i think we’re looking more at microwatt range or lower. Somebody on stackexchange measured power output of phone nfc module, and - measuring power received at secondary of air-core transformer - got 0.8mW. Assuming it’s representative, if all that power was fed into phone-sized magloop (10 cm square made out of 6 mm copper pipe) then at this frequency (13.65 MHz) we’re getting some -30dB efficiency so 800 nW. This is already very charitable overestimate, because NFC antenna is smaller, thinner, printed and multi-turn, and does not behave like magloop at all. Any response from passive device would be much weaker still. All of that uses high data rate (wiki says that ISO/IEC 14443 says 106 kbps), and because these things are where people live, there will be also a lot of urban noise. I’m not saying it’s impossible, but it wouldn’t be that easy

HF ISM bands as used (NFC things etc) are probably in sub-mW power range, there are regulatory limits on field strength and 27 MHz is additionally limited to 10 mW EIRP. Unless you have curtain that can hear signals from the future i don’t think there’s a lot to listen

If you delete account on twitter it doesn’t stay marked as deleted, anyone can register that name later. But this would have had to happen before 2015, if they were EA mockers after that then some kind of takeover seems more likely (who knows how many people posted from there, maybe one of them changed sides for whatever reason and locked out others)

also, “stealth pandemics” lol try to say nanobot plague without saying nanobot plague

Considering that they think that chatbots are as important as nukes, there is a precedent https://en.wikipedia.org/wiki/816_Nuclear_Military_Plant

No, width is your design parameter. I’ve used 4mm wire because store ran out of 5mm wire, but 3mm would be fine too if you can make it work mechanically. Were it all in air with no plastic, width of both is such that impedances of matching section are close to 300 ohm. Plastic around it lowers impedance and makes wire appear longer. 2m antenna has 220 ohm matching section and it also works. Rectangular connection boxes also work but the ones i could get weren’t as stiff. The way it’s done, bottommost section can be clamped with a regular pipe clamp, it’s harder with a box. Either way 4 or 5mm is not thin on 70cm so impedance of dipole will be probably lower than 5000 ohm, and entire band is covered so it just works

Pick any material you’re comfortable with. Start with 1 wavelength + couple cm of wire, measure out 1/4 and bend it so that 1/4 length point ends up at the bottommost point. Tune by trimming (both arms, lengths of shorter and longer should stay 3:1) and match by moving feedpoint lower or higher (lower is lower impedance). That’s why I’ve made them this way, you can see marks from screw near feedpoint because feedpoint was moved a bit both sides during tuning. By the time trimming gets minimum SWR close to say 420MHz adjust feedpoint to get minimum SWR then alternate between trimming and adjusting feedpoint if necessary. Every mm counts, small trims are better done by filing the wire down instead of cutting it. Plastic needs to stay on during measurement. Keep some 1m of free space (without large metal things) around antenna during measurement

Paging @tasankovasara@sopuli.xyz for logistically efficient antennas

Most of the magnetic flux should be contained in ferrite, and the part that leaks is pointed at the middle of other ferrite so it shouldn’t induce anything. This is fine

exactly, the ferrite only affects common mode current. you can think of coax as being composed of 3 conductors, core, interior of shield and exterior of shield. above some frequency and below frequency where coax starts to work like a waveguide, internal surface and core carry opposite currents (differential mode), and external surface carries common mode current. these can be treated as separate, except at the ends, because of skin effect. but also you can use twisted pair, because differential mode currents cancel out there

that’s just a piece of wire, perhaps some thin steel rope in a heatshrink attached to center conductor and trimmed to length. 1/4 wave at 2m which is fine, 3/4 wave at 70cm which means it’ll radiate most of energy upwards (wasted) when put on a conductive plane. this works because the other half of antenna is low power, handheld radio and operator (coupled by hand capacitively). putting 100W into it would be a bad idea because all that current will travel along the coax down to radio and operator except this time there’s an option of rf burns. for this kind of money, i’ve made two jpoles with extension cables, and the most expensive part was enclosure

i’ll make a post over the weekend about j-pole antennas that i’ve made recently. one of them even looks halfway professional