[HN Gopher] Rain Backscatter on 10 GHz
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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...
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(page generated 2021-06-06 23:00 UTC)