rtl-sdr uses the same chip as dvb-t tuners, but the everything else part is completely different

lol as if they could plan this far forward

cancer is in large part an old people disease, if you avoided dying of cholera you’re more likely to die of something else. also now there’s a lot of people who were exposed to carcinogens decades back, and we got better at treating pr preventing some other common causes of death like stroke or heart disease

that’s no problem at all, systems like that are in use

It’s easier to freeze water than to cool rock borehole

Saudis parked fuckload of money in ai startups

Lithium-iron is about 2x more expensive, there might be different availability and energy use during manufacture is probably higher

Lead-acid batteries work if you don’t care about weight and lithium-iron phosphate if you do

there are photos of 16 different radios and a couple of antennas, but the one in thumbnail is Elecraft KH-1

It’s up for you to decide. On U/VHF you can talk to other people directly (locally) like on HF. But you can also do things that HF can’t provide, or provides with limitations, like talk through repeater (uncommon on HF), or to ISS, or through satellites (HF bounces from ionosphere) or do longer distance communications from mountaintops, or do image transmission or packet radio (HF has less bandwidth). On receive only you can also download NOAA weather satellite images, or whatever else data are emitted by them. You can make your own repeater from two baofengs. HF gets affected by space weather, U/VHF is not, and we’re entering solar minimum. 6m will take you far further than 2m but it’s usually bundled with HF radios

On higher end there’s also moonbounce, but it’s not in the budget category

e: there’s 50 things you can do with SDR only (many on U/VHF) https://blinry.org/50-things-with-sdr/

Depends on what you want to do. UHF/VHF handheld radio can be had for 20-30, uSDX or QMX type small low power HF radio is closer to 100. You’ll also need battery, antennas (perhaps tuner) and something to put data in and out (headphones and microphone or cw key or audio interface to laptop) (no idea if it’s good but people use it)

this also happens with dc once voltage is high enough

It’s easier to see that this circuit is rather symmetric when you redraw it

Then with both switches closed blue wire (the one in the middle) should only carry small current. If both halves are exactly the same it should be zero

In general when circuit doesn’t include nonlinear components (semiconductors most commonly) you can sum two valid solutions and you’ll get another valid solution. Note that when one switch is closed, current in blue wire goes one way and when the other is closed, in opposite way

Could be. Amplifiers are a bit more complicated and there are many things that can limit bandwidth

If we consider groundplane antenna, which should be much better than anything that you can fit on a HT, it might be centered on 145MHz (region 2 band) and it’ll be good for 10MHz for 1:1.5 SWR (140-150) and 17MHz for 1:2 SWR (136.5-153.5) according to some random measurement, first that i found. Outside of these ranges SWR rises rapidly and if you tried to transmit on say 170MHz you might get SWR 1:5, perhaps 1:10 or worse if you’re unlucky. On receive this doesn’t matter too much because these nano- to microwatts of rx power would just bounce back harmlessly with the only effect being that apparent signal strength is lower. But if you tried to transmit then design currents or voltages would be exceeded and something will break, usually final stage of amplifier. This gets rarer than it used to be because some radios can measure SWR and will reduce power in such scenario. This also gets worse the higher transmitted power is

This happens because unlike on HF + 6m, on 2m and up ATUs are not a thing* and all antennas are expected to be matched. So you can use the same radio on GMRS or PMR or what have you and on 2m or 70cm band, but you have to change antennas between these uses. If you want to use all of these on one antenna, then there are special wideband designs like LPDA but this makes sense on a mast and not on handheld radio

* there are tuner designs that work on 2m and up, but you won’t find them in HT, there’s no point, they’re too big, too heavy and too expensive

Even if you tried and made it to work, there might be other incredible problems with things like harmonics or other spurious emissions because filters were not designed to work way out of these frequencies. For example you can try to force Quansheng UV-5K (?) to transmit on 60-ish MHz but most of the power goes out at 2nd and 3rd harmonic, because of the way filters were set up. Narrowband designs are much easier and this is what you’ll see all the time in amateur radio. Wideband and ultrawideband designs are constant source of job security for RF/microwave engineers

You can think of matching units and antennas (and to some degree even feedlines) as filters to some degree, because their bandwidth is not infinite

Note that there’s 25% of fractional bandwidth in there and many antennas won’t work everywhere in that range (and also other elements like power dividers, diplexers etc if part of circuit)

related phenomenon. at calm solar surface, there’s only hydrogen and helium. these are excited thermally and can emit radiation, but the highest energy photon they can emit is ca 13eV and 52eV respectively. this is vacuum UV, and this is what is responsible for ionisation of ionosphere even during solar minimum, mostly F layer. but when solar flare forms, there are these giant loops of charged particles, and when charged particles change direction or brake, they release a lot of high energy radiation, that is xrays. xrays just go everywhere and this is partially what is responsible for extra ionisation of ionosphere during solar maximum, and this contributes more to E layer ionisation. (because xrays can go further through air) when solar flare hits the earth, protons from it cause extra ionisation in D layer and this is why post-flare blackouts happen

this is also why one metric of solar activity is solar xray flux

there are also solar xrays, which also ionize ionosphere and are associated with CMEs (regular processes on surface of sun cannot make much xrays, it’s only when high energy particles are smashed back at the surface xrays are emitted. intense magnetic fields are needed for that)

Huh weird. There must be something evil in that pole, it might be a piece of metal or maybe it’s wet or rotting inside. I’d use plastic things to tie it, because natural fibers will remain wet some time after rain, that might degrade performance. (zipties or nylon fishing line or whatever preferably monofilament). I see that bottom is secured too, this is good because in wind antenna could flap around and would stop working if it’s too close to the pole. If twin lead is slightly twisted and under strain (half turn per 30cm or so) then it should flutter less in wind, but you’ve got it spliced and i’m not sure how that would work. This is likely fine as is

J-pole type antennas are effectively monoband. They might work on 3rd harmonic which would be here 70cm band, but most of signal in this case goes up and down that is it’s useless and the signal that goes out horizontally is 6db weaker than what it would be with J-pole for that band. So you can take more precise measurement by zooming in to 130-160MHz or even 140-150MHz, this way you’ll see how low does SWR go at band edges because now you can only see that there is minimum somewhere in the band. I don’t know how much your radio tolerates, but 1:1.5 is generally pretty good. On receive only it might be good also at other frequencies, but dedicated antenna would be likely better

I don’t know if you have calibrated your VNA with cable or not, you can use Smith chart if you do calibrate it with cable but without it, SWR shouldn’t change too hard with any reasonable length of cable (Smith chart rotates once per half wavelength of feedline). This is useful especially if you make your own antennas, but here it’s fine just to make sure that SWR is low

50mm^2 for 125A, just under 8mm diameter solid copper rod if it was solid copper rod. but it’s stranded so it’s a bit bulkier than that, bundled five per cable. it adds up to some 4cm in diameter