Skip Navigation

User banner

skillissuer

@ skillissuer @discuss.tchncs.de

Posts
16
Comments
874
Joined
3 yr. ago

i should be writing

  • Single stub tuning for nonresonant UHF antenna

    Jump

  • 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

  • Single stub tuning for nonresonant UHF antenna

    Jump

  • 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?

  • Single stub tuning for nonresonant UHF antenna

    Jump

  • 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

  • Single stub tuning for nonresonant UHF antenna

    Jump

  • 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

  • Amateur Radio @lemmy.radio
    skillissuer @discuss.tchncs.de

    Single stub tuning for nonresonant UHF antenna

  • Over 160 Chinese nationals fight for Russia in Ukraine and "Beijing knows about this," Zelensky says

    Jump

  • Over 160 Chinese nationals fight for Russia in Ukraine and "Beijing knows about this," Zelensky says

    Jump

  • 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

  • Deleted

    Permanently Deleted

    Jump

  • 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%E2%80%93Pakistan_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

  • now draw her

    Jump

  • Sam Altman’s Studio Ghibli memes are another distraction from OpenAI’s money troubles

    Jump

  • i thought it's A Guy in India

  • Poland only has enough supplies to fight war “for a week or two”, says security chief

    Jump

  • Poland only has enough supplies to fight war “for a week or two”, says security chief

    Jump

  • there's not that many of them and one Trident missile costs only $31M

  • Poland only has enough supplies to fight war “for a week or two”, says security chief

    Jump

  • what are they bombing yemen for?

    Jump

  • 10 years? since 90s more like

  • Poland only has enough supplies to fight war “for a week or two”, says security chief

    Jump

  • i think there was an update or two since

    also the minimum deterrence always kept up by brits is that there's at all times enough nukes in submarines to destroy moscow. french have some more fine-grained options

  • Poland only has enough supplies to fight war “for a week or two”, says security chief

    Jump

  • triple the defence budget

  • If u use a SWR meter u vibe checking ur antenna

    Jump

  • okay i see now

  • If u use a SWR meter u vibe checking ur antenna

    Jump

  • but what if you put another split ring inside it, it'll be different

  • If u use a SWR meter u vibe checking ur antenna

    Jump

  • this is just small-ish magloop

    i've seen some people make magloops out of bike rims, it's similar sized. the smaller it is the lower radiation resistance, higher currents and voltage on capacitor, narrower bandwidth, and lower efficiency. i don't remember how it scales but efficiency goes up fast with size, 1m dia magloop is already better. downside is that tuning becomes impossible on higher bands (capacitance required for this is below minimum capacitance of capacitor that you have)

  • If u use a SWR meter u vibe checking ur antenna

    Jump

  • will it antenna? i think it will

    split ring resonator has already two different lengths of paths so - even without accounting on how these two interact - you could expect two different frequencies where it's resonant, with peaks perhaps overlapping to a useful degree making a decently wide band possible. it looks a bit like halo antenna with parasitic, downside being that it's probably a bit hard to feed it, circumference has to be halfwave on lowest frequency and if made for HF it'd be gigantic

    i think it's more useful to think of magloop as extremely shortened, low impedance, low bandwith halo antenna

  • DUI hiring just works

    Jump
  • NonCredibleDefense @sh.itjust.works
    skillissuer @discuss.tchncs.de

    90% of Russian leaders quit right before they're about to establish warm water port for good

  • NonCredibleDefense @sh.itjust.works
    skillissuer @discuss.tchncs.de

    You heard it here first: Bashar Assad might be dead

  • NonCredibleDefense @sh.itjust.works
    skillissuer @discuss.tchncs.de

    There are people who slept through the entire thing

  • NonCredibleDefense @sh.itjust.works
    skillissuer @discuss.tchncs.de

    NATO or nukes, remember?

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    mopup rule

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    4k ultrahd rule

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    suspicious rule

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    foraged rule

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    pain rule

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    throw away "do not eat" rule

  • 196 @lemmy.blahaj.zone
    skillissuer @discuss.tchncs.de

    cyberpunk is now rule

  • NonCredibleDefense @sh.itjust.works
    skillissuer @discuss.tchncs.de

    Mind your business, citizen. Mystical weapons aren't real

  • Science Memes @mander.xyz
    skillissuer @discuss.tchncs.de

    i was fourth author in a mdpi paper and now i'm drowning in spam please help

  • NonCredibleDefense @sh.itjust.works
    skillissuer @discuss.tchncs.de

    remember to stay hydrated