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Comment: One Photon Return Per Laser Pulse? (Score 1) 43

by Fleetie (#45215287) Attached to: Laser Communication System Sets Record With Data Transmissions From Moon
Conventional wisdom was that the lunar distance ranging, using the lunar retroreflector arrays, averaged 1 photon or less returned to the Earth detector, per outbound laser pulse.

Now presumably, this 622 Mbit/sec was outbound only (Earth to Moon) and not a return trip. So that will help quite a lot.

But to get these remarkable bandwidths, the Earth-based laser and beam expander/collimator must be pretty special.

Does anyone know the juicy figures like: Laser wavelength, energy per pulse, pulse rep rate, and so on? Oh, and the strength of the signal received at the moon, in (I dunno) photons-per-bit or something?

Comment: Re:Still sceptical (Score 5, Insightful) 168

by Fleetie (#42284931) Attached to: Electrical Grid Hum Used To Time Locate Any Digital Recording
Re: Location: Wrong. The entire UK grid is "locked together" and it all runs at the same frequency. Necessarily. Also: Recorder doesn't need to be plugged into the mains. 50Hz hum permeates the space around us. Try grabbing hold of an oscilloscope lead and look at how much 50Hz hum you are "carrying". Unless you're a long way from mains outlets, it's a lot.

Comment: Stop Calling Mars "The Red Planet"! (Score 0, Flamebait) 228

by Fleetie (#40943075) Attached to: Upgrading Software From 350 Million Miles Away

There is this global media obsession with referring to Mars as "The Red Planet". It is really irritating.

Mars has a name, just like all the other planets in our solar system: Its name is "Mars". So use it, and respect the planet and its name.

It's so irritating and "media lovvie". Also, the planet it not really "red" at all. It's brown. It belongs in exactly the same category as media types referring to scientists as "boffins". It's RUDE and DISRESPECTFUL.

I wish the media would shed this ridiculous obsession with ignoring the name of the planet MARS.

Comment: Re:Colors (Score 1) 127

by Fleetie (#36220674) Attached to: New Laser Data Transfer Rate Record Set At 26 Tbps
For exactly the same reason that you can't fit an infinite number of AM radio stations into a finite width of radio spectrum. The act of AM-ing a single frequency carrier f_c at data rate / frequency f generates sidebands each side of the carrier, so that the signal now spreads over (f_c - f) to (f_c + f), i.e. the bandwidth becomes (IIRC) 2f. Fleetie

Comment: Re:Well... (Score 2) 317

by Fleetie (#35089066) Attached to: 19-Year-Old Makes Homemade Solar Death Ray
The concentrated spot of light cannot even be quite 1 x the brightness of the sun. Never mind ">5000 times brighter". The laws of thermodynamics say so. You cannot focus an image of a light source so as to make the intensity at that focus more intense than the light source itself. Kudos for good execution of his idea, but that ">5000 times brighter" claim is just plain wrong.
Communications

Testing and Mapping a Cellular Data Network? 114

Posted by kdawson
from the circles-and-arrows-on-the-back-of-each-one dept.
bgsneeze writes "In order to resolve an ongoing issue with a vendor, I have been trying to find a way to test different 3G data devices empirically. I would like to be able to chart signal strength, latency, and bandwidth. I would also like to create a map of the coverage area. I have a test 3G card from three different providers. I would like to be able to travel with the setup to several different locations and run tests. What software or techniques would Slashdotters use to test the different devices? Are there any free or open source software packages that will do this?"

User hostile.

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