[HN Gopher] Rain Backscatter on 10 GHz ___________________________________________________________________ Rain Backscatter on 10 GHz Author : parsecs Score : 60 points Date : 2021-06-06 17:58 UTC (5 hours ago) (HTM) web link (destevez.net) (TXT) w3m dump (destevez.net) | jcims wrote: | Hopefully the mass production of X-Ka band phased array antennas | for Starlink and Kepler will bring the costs down for general | purpose equipment. It would be really cool to be able to 'see' | the signal bouncing off of clouds and whatnot in the form of a | raster image vs 2d fft. | guessbest wrote: | Is this like the ham radio site? | http://www.wa1mba.org/10grain.htm | _Microft wrote: | Yes, the experiment conducted on the submitted website looks a | lot like the "Storm 1" example situation in Figure 3 on the | page you linked to. | oblak wrote: | I guess the site got fried | CraigJPerry wrote: | Maybe not on the 3cm (10GHz) band but on 13cm (2.3/2.4GHz) and | even 70cm (430/440mhz) there's quite a lot of activity with | aircraft scatter. | | I'm still in awe that you can bounce a signal off a plane and get | a useful and predictable bounce off it. | | http://www.airscout.eu/screenshots.html | anonymousiam wrote: | Meteor scatter is also a popular amateur radio mode. Brief | VHF/UHF contacts are possible by reflecting off the ionized | meteor trails during any of the 30 or so meteor showers per | year. | | https://en.wikipedia.org/wiki/Meteor_burst_communications | | https://www.electronics-notes.com/articles/ham_radio/amateur... | coding123 wrote: | Something is wrong with the database, it's a PHP site... | geocrasher wrote: | It's WordPress, and the database can't be connected to because | it's probably maxing out the number of MySQL connections. | | If you're the owner of the site: Get some caching installed. I | like WP Super Cache and Autoptimize, they're a great combo. | | For reference: My WordPress site got hugged on the front page | of HN yesterday, didn't bat an eye. | rrdharan wrote: | Kind of boggles the mind that some form of these aren't yet | the defaults / built-in after all these years.. is it just | too hard to integrate into the core out of box install for | some reason? | throw_m239339 wrote: | > Kind of boggles the mind that some form of these aren't | yet the defaults / built-in after all these years.. is it | just too hard to integrate into the core out of box install | for some reason? | | Because not all hosting providers compatible with Wordpress | are compatible with these caching addons, it's as simple as | that. Wordpress runs on the lowest sane PHP+Apache+Mysql | environment. | | Now I can't access this website but it looks like it | doesn't need to run on PHP, it should be using a static | site generator. | joecool1029 wrote: | Many different kinds of server environments where cache | configuration isn't the same and many kinds of sites where | some things really shouldn't be cached (shopping carts, | admin panels). | coding123 wrote: | I don't know, Wordpress had like what, 1 billion years to | wrap it's connection manager to do auto-caching for | anonymous users - I mean a 15 second cache internally | managed by files on the disk in the temp folder would | have instantly made Wordpress be fault tolerant during a | hug of death. | joecool1029 wrote: | I get the criticism but looking at the history of caching | plugins' security issues and the commonality of screwed | up caching, it's obvious there isn't a one-size-fit-all | solution. | | Rather than dynamic caching, most users wanting to | survive getting hugged on a simple blog would probably | best be served by one of the static site generators for | Wordpress. Takes out the main bottlenecks and leaves a | lot more flexibility in how to serve it. | geocrasher wrote: | One of WordPress' primary strengths is that it's extensible | and does not do anything big by default. One of its | weaknesses is that its so easy to use. No difficult | configuration is necessary and most web hosts have an auto- | installer for it that configures it with default settings. | The web host I work for does have a plugin that fixes a lot | of these things (caching, wp-cron, basic security issues, | etc) but it's not a panacea. There just isn't one. | TchoBeer wrote: | Ease of use is a weakness? | maweki wrote: | I think they meant that not having to think about | anything makes people not think about anything. | geocrasher wrote: | Technologically speaking, yes. The default configuration | works but there are problems when the site becomes busier | that show up. | | For example: WordPress has its own scheduler called wp- | cron.php. Part of the ease of setup is that you don't | need to create a cron job. It will just run wp-cron.php | every time there is a page load. While that makes it very | convenient it doesn't scale well and so when a site | becomes busy it starts to fall over. So in that sense | it's ease of use is also a downfall at times. | unclemase wrote: | Link to Tweet: | https://twitter.com/ea4gpz/status/1401598857478279173 | _Microft wrote: | Does the scatter volume have to be kept small so that when the | signal gets scattered at different positions, the path lengths | and thereby the delay of the scattered signals do not diverge too | much? If they did, the received signal would be "blurred" by | receiving the signal overlayed by itself but with different | delays. Is this the correct explanation here? | timeinput wrote: | I think it probably has more to do with path loss than the | multi-path effects that the rain drops would have. That is the | reflection from water in the cloud only has to travel through a | smaller amount of rain than it might if you were doing it over | a terrestrial network, but I definitely don't know all the ins | and outs of CW transmission. | unixhero wrote: | This was cool, but I have no idea of what was achieved or what | the significance of it was. Other than it was possible to receive | a signal during heavy rain. | lucb1e wrote: | Sameish here. I get the significance, like, it's cool in | general to be able to receive other things when the rain | somehow scatters it, but I understand very little about why | rain makes it possible. Isn't rain supposed to block 2.4GHz and | nearby frequencies? Is 10GHz also affected? Why doesn't it | block but reflect? Does the moving of the rain have anything to | do with it, is that why they're seeing a 20m/s doppler effect? | Speed of light in water is maybe different, does it refract and | then come out on the other side after having moved down? If | someone could give a "Too Dumb; Didn't Understand" version of | the article, I'd be interested! | anonymousiam wrote: | Since nobody else answered you, yes, the falling rain creates | the observed Doppler frequency shift. This guy must have some | pretty good instrumentation to be able to accurately detect a | 700Hz shift in an X-band carrier. | vvanders wrote: | https://en.m.wikipedia.org/wiki/Radio_propagation covers it a | little bit. The short answer is that wavelength(aka | frequency) vs raindrop size causes signals to scatter instead | of attenuate and you can pick up a fraction of the original | signal. | ac29 wrote: | Rain itself doesn't "block" 2.4GHz signals per se, though any | obstruction will cause some degree of radio wave attenuation. | Attenuation is higher at 10GHz and above, since the | wavelength is shorter: higher frequency = shorter wavelength, | and shorter wavelengths are obstructed by smaller objects. | | That being said, wet trees are more effective at attenuating | non line of sight radio signals than dry ones, even at 2.4Ghz | and below. So while the raindrops themselves have minimal | effect for sub-10GHz signals, you can see signal fade in wet | conditions. | timeinput wrote: | It's probably not super "significant", but it's neat. Someone | has a light bulb (the omni-directional beacon) 40 km away, and | completely invisible if you go looking for it (from his ground | station location). | | The author pointed a telescope (his directional ground station | antenna) straight up and on a rainy day and could see the light | bulb turn on and off. | tyingq wrote: | Microwave reflections/refraction off of the rain made the | otherwise blocked line-of-sight signal temporarily not blocked. | | This is also how "troposcatter" shots work with microwave | radios. If the distance between two stations is too far for | line-of-sight (due to earth curvature effectively being a | "hill" in the way), you can bounce the signal off of the | troposphere. | _Microft wrote: | The site is still having troubles but Bing has got a cached | result now: | | https://cc.bingj.com/cache.aspx?q=10GHz+rain+backscatter&d=7... ___________________________________________________________________ (page generated 2021-06-06 23:00 UTC)