I don’t know if you need common current mode choke like this, it’s probably overkill, popping 3-4 ferrite beads on normal sized coax should be enough. Some people don’t even use it at all and things still work for them. You can also always use folded balun or sleeve balun as a common mode current choke. This toroid is only 20mm in diameter or so, and RG174 has minimum bending radius 6mm, so it’s abused a bit but not that much. It’s probably good for lower bands like 6m too. Alternative is to use a pair of twisted wire in parallel (these have 100 ohm impedance or so, two in parallel are closer to 50) wound on ferrite (more common on HF), and if size restrictions exist, you can use tall and narrow non-split ferrite bead instead of wide and short toroid like this one i’ve used. Also i made it this way because that’s what i had in my drawer. Maybe it was not balun that was narrowband, but radiating element is a limitation instead?
i should be writing
- 46 Posts
- 3.08K Comments
that’s RG174, there’s only 25cm of it or so, so loss is probably not a huge concern (53dB/100m at 400MHz, so 0.13dB), and that common mode choke is probably a bit too much anyway
not much? i don’t have scale but 150g perhaps? i think that if you don’t need it waterproof then you can just extend wires, use them for support and get rid of case entirely. this would require sturdier shorting bar and some spacers probably but would be more compact
it’s 80cm long and can’t be folded, so if that’s portable enough for you, then yes
the point of this antenna is that it has something about 2-3dB gain over dipole, if you don’t need this a lots of smaller antennas with dipole gain exist
e: and also despite what its size could suggest it’s a single band antenna, this one is for 70cm but if you have space for 2m (2.3m long) then i think it still should be practical
91·4 个月前mercenaries would be something like wagner. there are international volunteers within normal units of UAF, with normal pay and responsibilities just like any other unit. these chinese were promised unusually high salary and russian citizenship at the end of the contract. ukrainian foreign legion is entirely official, while this chinese recruitment seems to be covert or at least not very highly visibly public. ukrainian foreign legion also takes only people with former combat experience (iirc), it’s unclear so far if chinese recruited have any, probably not considering that china has stayed out of any major war or deployment since forever. these are not the same things
3·4 个月前additional layer is that according to comments first track is also used in chinese nature documentaries
in some cases, on the power of the “fuck that other other guy” school of geopolitics, this can be avoided. https://en.wikipedia.org/wiki/2024_Iran–Pakistan_border_skirmishes “you see, we actually targeted separatists” “yeah we also targeted separatists let’s call it even” it also requires certain degree of diplomatic finesse that trump lacks, and there’s no good reason for strikes in the first place considering that dea coordinated with mexican police (?) previously, so they could just continue doing that
of course MBA came up with this
an airplane doesn’t flap its wings
now you’ve got me thinking if storage in fridge is necessary at all, if these are salts. worst thing that can reasonably happen is that salt picks up some water from the air, on top of water condensing on sample when vial was opened while still cold. freebase would probably be air-sensitive, but for compounds that are known sensitive i’d put them under argon/nitrogen, tape vial shut (with normal electrical tape, not parafilm) and store in freezer instead. sigma lists storage temperature for MDMA analytical standard (weak solution of freebase in methanol) as -20C, but some of this might be legal cover with excess requirements for cases where you’d have to be absolutely sure that analytical standard didn’t decompose (like in evidence in drug cases)
there was a reddit ama with an ukrainian dude who was in charge of procurement of certain drones for ukrainian army. among these were uavs from anduril, and uaf decided not to buy them, chiefly because these drones don’t work and cost something like 20-50x more than equivalent ukrainian designs that do work. the reason why they don’t work is russian jamming, about which anduril people presumably were informed, yet somehow they still were complete assholes (to foreigners only) through entire process. which also means that ukrainian elint captured how russian jamming works, gave that data to anduril who proceeded to do fuck all with it, possibly leaking this intel in some signal chat
the reason why these were on the table to begin with is that (part of) american weapons aid is provided in form of money to be spent at american manufacturers, it’s not pallets of cash like fox news would like you to believe. (private donations to places like united24 do work this way, but also for example denmark does provide money with no strings attached, at least not these). (yea i’m effectiving my weaponized altruism, cranking up these numbers of dead russians per thousand euros). reasons for that are slight wage discrepancy between poltava and berkeley, compounded by scale (how many drones does anduril make per year, 20? ukrainians make low millions, probably with thousands to hundreds of thousands per type). most of costs in drone development is driven by software. doesn’t help that thiel’s people are swamped in vc money, therefore they don’t have to work efficiently, neither have their drones, or even they don’t need to work at all. ukrainians don’t have the luxury to blow millions into ai swarming that doesn’t work and instead put that effort into signal processing to avoid jamming, which does work, which they can check pretty quickly too.
this is the disruption they’re cooking. invest in eastern europe or something
6·5 个月前i thought it’s A Guy in India
another solution:
take duck, carrot and potato at once. if boat is fine if you put duck and carrot in but will sink if you put in duck, carrot and potato then you’re already on horrifyingly narrow engineering margins and probably shouldn’t use it in the first place
in the worst case you can put duck on a leash if it’ll run away otherwise
there’s technology transfer from koreans https://www.polska-zbrojna.pl/home/ArticleShow/42536
also not everything can be done with drones, for some time-sensitive targets you need speed that MLRS delivers
4·5 个月前yeah, you better do
there’s not that many of them and one Trident missile costs only $31M
both 198Au and 199Au have half-life in order of 3d, waiting 1y will decrease radioactivity to nothing (5E40 times for 198Au and 1.3E35 times for 199Au. others are shorter-lived and fission products can be probably separated chemically to an acceptable degree). it’s also pretty decent deterrent against stealing it, and decay product mercury is stable and easily separated. i’m not even sure if irradiating gold with neutrons would make it worthless because of that. might even go up in value because there’s now a story behind it. bigger problem would be that it’s scattered everywhere
Check first on a smith chart whether transmission line that you can easily make or get and adjust its length has proper impedance for both source and antenna. The shorter length matching section has, the wider bandwidth you’ll get. There are typically two solutions, of which one is better. Ideally you’d like to have transmission line impedance a bit lower than what would be needed if only transmission line part was used (without stub)
If you want to make a yagi, or mount antenna close to a mast and don’t care particularly hard about extremely uniform coverage, you can modify impedance by changing distance to reflector. If you want to use something like this https://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf then this antenna (radiating element) is already unbalanced and doesn’t need balun that badly