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Communications Network Science

No Wi-Fi Around Huge Radio Telescope 224

Posted by Soulskill
from the makes-a-strange-sort-of-sense dept.
JG0LD writes "Students at a tiny Appalachian public school can't use Wi-Fi because any such network can throw the radio equivalent of a monkey wrench into a gigantic super-sensitive radio telescope just up the road. GBT's extraordinary sensitivity means that it's very susceptible to human-generated radio interference, according to site interference protection engineer Carla Beaudet. 'If there was no dirt between us and the transmitter, a typical access point ... would have to be on the order of 1,000,000 km [more than 620,000 miles, or about two and a half times the distance from the Earth to the Moon] distant to not interfere. Fortunately, we have mountains around us which provide lots of attenuation, so we're not seeing everything from everywhere,' she said. A standard Wi-Fi access point would wipe out a significant range of usable frequencies for the observatory. 'It simply ruins the spectrum for observations from 2400-2483.5MHz and from 5725-5875MHz for observational purposes,' wrote Beaudet."
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No Wi-Fi Around Huge Radio Telescope

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  • Re:Low power wifi? (Score:5, Interesting)

    by SternisheFan (2529412) on Friday February 08, 2013 @07:17PM (#42839251)
    In three years it won't be an issue. From the article:

    "here is a technological solution to the problem in the pipeline -802.11ad, a next-gen wireless standard that uses 60GHz frequencies to send and receive information, instead of the usual 2.4GHz and 5GHz bands. At 60GHz, according to Beaudet, radio energy essentially just bounces off the atmosphere -meaning that the frequency is useless to the Green Bank Telescope in the first place. Signals to and from 802.11ad access points, then, would have no effect on the work taking place at the GBT, allowing for the best of both worlds. Unfortunately, 802.11ad is very much a technology of the future, not of the present -experts at an Interop New York panel last year predicted that devices using the standard wouldn't hit the market until 2014."

  • by Anonymous Coward on Friday February 08, 2013 @08:02PM (#42839653)

    NRAO Green Bank has several telescopes, a few of which are funded by organizations other than NRAO. Most notably, the 140 foot dish is currently funded by a project from MIT. There are also many other educational program that run at Green Bank that are not the GBT or VLBA, such as the small 40 foot dish which is available for school trips & amateur astronmers. The article is not clear about the fate of these other programs at NRAO Green Bank.

    I grew up in West Virginia, and took a trip to Green Bank in 8th grade where our teacher had reserved time for us on the 40 foot dish. We were allowed into the control room, and were instructed on how to aim the dish at a celestial object that was in view during our visit. And that was separate from the liquid nitogren demonstration they had for us as well. For the most part, Green Bank is looked upon favorably by those in the community around it.

    If you want to get to odd rules about NRAO Green Brank, how about the fact that there is a keep-out zone for standard gasoline engines near the 'scopes. Only diesel vehicles may be used on the observatory's grounds, due to radio emissions from spark plugs.

  • Re:This is news? (Score:5, Interesting)

    by Sipper (462582) on Friday February 08, 2013 @08:22PM (#42839771)

    I've visited the GBT while it was under construction at the NRAO; there's another interesting feature of the site due to the location being surrounded by mountains -- which is that thunder from lightning strikes take a long time to dissipate, because they reverberate between the mountains. It's reallly something to listen to -- the rumble after the initial thunderclap lasts for about 20 to 30 seconds. :-) Somehow it's like a symphony to the soul.

  • Re:This is news? (Score:5, Interesting)

    by Sipper (462582) on Friday February 08, 2013 @08:39PM (#42839913)

    > That is a serious infringement of Liberty, IMHO.

    Your liberty does not include the right to spray your rf all over my land.

    Actually in most places, it does, at least for Ham Radio operators, CB, Family Radio systems, wireless intercoms,and Wifi. However as you mentioned, these liberties also come with the restriction that the transmission not interfere with other frequencies -- thus we can give you our RF, but you should never notice.

    There's one catch, though: modern TVs lack an input filter that they're supposed to have by design which would normally reject non-TV frequencies, because they're suppposed to be tolerant of out-of-band signals. TV manufacturers got permission not to ship this filter, because most TVs are hooked up to Cable where it isn't needed. However in the cases where a neighbor of a Ham is receiving broadcast TV, the TV can be desensed due to the lack of the filter and the close proximity of the transmitting Ham station. In those cases filtering needs to be added back to the TV to isolate it from the Ham transmissions -- it's my understandnig that this filter can be provided by the TV manufacturer upon request.

  • Lunar telescopes (Score:5, Interesting)

    by Areyoukiddingme (1289470) on Friday February 08, 2013 @08:42PM (#42839933)

    This is why the proposal to build a radio telescope array on the far side of the Moon has been around for so long. Having the moon between us and it is one helluva lot of dirt for blocking stray signals. Plus no atmosphere to get in the way. All you have to worry about then is reflection of Earthly signals off of other bodies in the solar system.

    Too bad about the expense...

  • by omarius (52253) <omar@allwron[ ]om ['g.c' in gap]> on Friday February 08, 2013 @09:00PM (#42840089) Homepage Journal
    This is the second post I've seen in as many days on Green Bank, and no mention of the fact that the NSF is planning on closing the facility to save money. Green Bank is the largest movable radio telescope in the world. If you feel--like I do--that this would be a detriment to the nation, please sign the petition [change.org] or, even better, write your Congressperson.
  • by Almost-Retired (637760) on Friday February 08, 2013 @09:33PM (#42840327)

    If they really need to use the frequencies that a technologically developed society uses all the time, then they should build their instruments in a remote enough location that regular use of technology would not be likely to interfere with them, instead of building it near enough to a town or city that a school could reasonably pose a threat just by using wifi.

    Well now, aren't we the social experts all of a sudden? The National Radio Astronomy Quiet Zone, aka the NRAQZ, was setup in the 1950's as someone has already pointed out, and it is a natural bowl with 3 to 5 miles of real estate that is shielded from a lot of earthy interference because of the surrounding hills.

    In 1950, there may have been some daytime AM radio in the area, which is not much of a problem because they don't listen to much below 300 mhz, 300 times the frequency of a Ma & Pa radio station. Its (the ma & pa radio) still there too.

    Interesting side effect was that distant tv stations were forced to either be low band vhf, or if high band, more limited in power output. WTDV, on channel 5, about 80 Mhz, built their original facility on Fisher Hill, which was actually about 2 miles inside this designated areas borders, and was put there by the FCC's rules & regs when it was built in the later 50's because it was the highest point, and could not be moved more than 2 or 3 miles from where it a was at without being short-spaced to some other station. But was allowed to use the full 100kw sync tip peak power that any low band vhf can us as a maximum ERP.

    WBOY, 17 miles north in Clarksburg and assigned to channel 12, was not allowed the high band vhf's max power of 330 kw ERP. but was limited to 100kw because of the slightly above 200Mhz frequency.

    So, in the run up to the digital conversion, they wanted to recover all the low band stuff for use by Law Enforcement & because their assignment program was written by an idiot that wasn't aware of the NRAQZ, and proceeded to assign both stations new channels in the 56-58 range. That's in the high middle of the 700Mhz range. So I called the enforcement/compliance officer at Green Bank and asked him how much noise I could make on channel 58. 58 don't mean nothing so I had to translate to the actual frequency, which he plugged into his program and which said that the maximum power I (WDTV, I was the C.E. at the time) could send from 270 degrees true to Green Bank was 4.78 watts. Anything more than that he would have us shut down. I said send me a letter to that effect, and he did.

    So I went to the NAB a couple months later and had a ball going around to the various transmitter makers showing that letter and asking for bids on a 4.78 watt transmitter. IOW, I had a ball poking fun at the commishes obvious stupidity.

    Eventually, along with some heavy duty prompting by our Washington legal people, they saw fit to let us stay on our low band frequency. Quite a few of the tv broadcasters in the more mountainous areas have also stayed on our original channels.

    As for de-funding or de-protecting the area from interference from the broadcasters, no way. 90% of what we know about the radio universe around us, came from Green Back, and to a certain extent, Aricebo. But while Aricebo can hear farther, it isn't nearly so steerable, nor as sharply focused as Green Bank's big dish. The new dish they built to replace the 300 meter that fell from rust & corrosion way back when, is performing at a level the old dish only dreamed about. It can move faster too in the event of a gamma ray burst, it can slew and be looking at the source of that burst in just a couple minutes. That facility is IMO a national treasure. FWIW, you have to take the bus into the place is your car has spark plugs. So everything that moves in that valley moves in a diesel bus, or by muscle powered bicycles.

    Like Paul Harvey would say, and that's the rest of the story.

    Cheers, Gene

  • Re:This is news? (Score:4, Interesting)

    by Jah-Wren Ryel (80510) on Saturday February 09, 2013 @03:08AM (#42841841)

    That location was chosen because of the way radio waves reflected off the moon and a few other things. It is essentially a focal point if you want to listen in to Moscow.

    How does that work, the moon not being geo-stationary and all?

The bogosity meter just pegged.

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