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Quiet Cellular Antenna Tech To Boost S. African SKA Bid

timothy posted more than 2 years ago | from the can-we-hear-them-now? dept.

Cellphones 38

slash-sa writes "Two South Africans have given their home country a boost with its Square Kilometre Array (SKA) bid by inventing cellular antenna technology which reduces 'noisy' emissions from cellular base stations in the area. They reduced emissions by using an antenna based on phased-array principles, providing omnidirectional coverage but also blocking the RF transmissions along a single direction (that would correspond with the bearing of the SKA core site). The antenna has been tested and performs extremely well. Trialling measurements have shown that the RF signal levels at the proposed SKA core site can be reduced significantly, while at the same time, much of the original GSM coverage can be retained."

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It's good to see (2)

SevenTowers (525361) | more than 2 years ago | (#37877270)

science still gets some funding. Amongst all the cuts we've seen in the past years, this is excellent news!

What is to stop Australians using this? (1)

walshy007 (906710) | more than 2 years ago | (#37877286)

What is to stop the australians from using similar things to this?

Re:What is to stop Australians using this? (0)

Anonymous Coward | more than 2 years ago | (#37877346)

Not 100% sure, but I think at the proposed site there isn't a GSM signal to worry about.

Re:What is to stop Australians using this? (1)

MichaelSmith (789609) | more than 2 years ago | (#37877582)

Not 100% sure, but I think at the proposed site there isn't a GSM signal to worry about.

Yeah Australia is great like that (:

Re:What is to stop Australians using this? (2)

smi.james.th (1706780) | more than 2 years ago | (#37877468)

Australia would be welcome to do something like this... I'm a South African EE student at the moment, I'm working towards an SKA related project, and whether or not South Africa is chosen ultimately, we have our own radio telescope plans, so this would be useful anyway.

The SKA is about international collaboration, AFAIK. It's good for countries to share inventions.

Re:What is to stop Australians using this? (3, Informative)

sirlark (1676276) | more than 2 years ago | (#37877502)

Apparently one of the big advantages the Australians have in the bid is that their site already has significantly less RF interference because of it's relative remoteness and much lower surrounding population density. However, that remoteness is a downside too, as it makes construction and supply costs much more expensive. This technology could really improve South Africa's chances, because apart from RF interference, they seem to have a stronger bid. The Karoo, being less remote, reduces costs for building, communication infrastructure, supply etc. Also, South African labour costs are cheaper. If this technology can reduce RF interference to comparable level with the Australian site, it'll be great. Sure the Australians could use it, but my understanding is that there's so little RF interference at their site as to already be barely above the detectable threshold of the proposed SKA equipment. (Citation, drunken conversation two weeks ago with one of the people working on the S.A. bid)

Re:What is to stop Australians using this? (3, Informative)

thegarbz (1787294) | more than 2 years ago | (#37877998)

However, that remoteness is a downside too, as it makes construction and supply costs much more expensive.

This is actually one of the real forte's of Australia's construction force. Our many remote mining and gas projects which create a local town to sustain the business have basically trained a contract workforce and vendor supply chain easily capable of building massive projects in the middle of no where.

Though this is a double edged sword. The last gas plant I worked in recently had massive troubles finding qualified welders to work during their maintenance shutdown due to the amount of work going on around the country sucking up local resources.

god forbid (1)

decora (1710862) | more than 2 years ago | (#37881280)

the company pay to train people

Re:god forbid (1)

thegarbz (1787294) | more than 2 years ago | (#37882034)

That is not how construction works, and it's also not how training works.

It is incredibly rare that an internal company workforce will build a new project, it is almost always an external contractor which is bought in. A company who wants to build a gas plant has zero incentive to train people to build one as when construction is finished they are no longer needed and need to be replaced with a workforce of different qualifications (these often then do get trained inhouse).

Additionally a contracting company doesn't have incentive to train too many people due to the boom bust nature of the resources sector. Australia experienced quite a lull in new resources related projects so there wasn't a need to have or train a big workforce. And then suddenly the world got green, coal is not the flavour of the month, and gas plants, carbon capture and storage plants, and coal seam gasification plants started popping up everywhere.

A fully qualified welder suffers through quite a long apprenticeship, much longer than the current resources boom has been in effect. The construction industry is generally quite slow to react to sudden booms such as the one we are in. Some of the places that are hardest hit by this are established plants close to the city who's qualified trades people are being wooed by fly-in-fly-out deals and 6 figure salaries.

Re:What is to stop Australians using this? (1)

sirlark (1676276) | more than 2 years ago | (#37887910)

This is actually one of the real forte's of Australia's construction force. Our many remote mining and gas projects which create a local town to sustain the business have basically trained a contract workforce and vendor supply chain easily capable of building massive projects in the middle of no where.

Fair enough, but it still costs more... that cost is presumably hidden in the more expensive labour costs, exchange rates, etc. Not arguing that the Aussies can't do it, just that they're more expensive than the South Africans. Also, building a town around the SKA is precisely want should be avoided surely?

Re:What is to stop Australians using this? (1)

philcolbourn (1150439) | more than 2 years ago | (#37877572)

Nothing. But as other have mentioned, it is not really necessary. There are very few registered transmitters within 100 km: http://web.acma.gov.au/pls/radcom/site_proximity.nearby_sites_list?pMODE=DD&pLAT=-26.70417&pLONG=116.6589 [acma.gov.au] More info can be found here: http://www.acma.gov.au/WEB/STANDARD..PC/pc=PC_100628 [acma.gov.au] And transmission limits here: http://www.acma.gov.au/webwr/radcomm/frequency_planning/frequency_assignment/docs/ms32.pdf [acma.gov.au] And my rough estimate of Australia's SKA site: http://maps.google.com/maps?q=26.67s,+116.7e&hl=en&sll=-33.718613,150.617295&sspn=0.012244,0.022724&vpsrc=0&t=w&z=8 [google.com]

goat turds (1)

For a Free Internet (1594621) | more than 2 years ago | (#37877518)

are slimey!!!!!!!!!!

Not really necessary in Australia (1)

Anonymous Coward | more than 2 years ago | (#37877532)

Since the site is in Geraldton, which doesn't have a lot of GSM coverage anyway and very few radio transmissions, since it's so sparsely populated.

I hate neckbeards (0)

Anonymous Coward | more than 2 years ago | (#37877566)

I hate neckbeards

Good antenna: Yes, Getting it deployed: Maybe (4, Informative)

nroets (1463881) | more than 2 years ago | (#37877602)

Getting the antenna deployed is another matter. For example ICASA has serious corporate governance problems [itweb.co.za] .

I live in South Africa and I regularly pick up high power WLANs in my neighbourhood. And I suspect many of them are used to carry CCTV signals or to bypass the expensive telecoms operators. The public is sympathetic to these cause. So compliance with government regulations will not be very high.

What about the phones themselves? (1)

psychofox (92356) | more than 2 years ago | (#37877950)

It's a neat idea, but it doesn't solve the problem of the phones themselves being transmitters!

Re:What about the phones themselves? (1)

bruce_the_loon (856617) | more than 2 years ago | (#37878026)

The root cause of the problem is that cellular phones are about the only reliable communications method used by the farmers near the proposed site. Use of phones on the site itself isn't a problem as the operational rules would forbid it, but the towers needed to support the farmers would interfere.

By creating an antenna that can blackout a narrow sector - the site - while not affecting signal strength for the farmers, they eliminate the issue of interference without forcing the farmers to lose reliable communications.

I don't understand what's unique (1)

Maow (620678) | more than 2 years ago | (#37878552)

I did RTFA, but with my limited knowledge I didn't see what's unique with their use of phased array antennae.

Anyone able to elaborate? Is it unique because it's in the GSM band? Because it blacks out a very narrow area?

Re:I don't understand what's unique (1)

technoslash (2496310) | more than 2 years ago | (#37880818)

There is nothing unique about phase array antennas, or anything challenging about applying them to the GSM band. It is probably unique since the technology is only required when providing farmers mobile phone access close to large sensitive radio astronomy telescopes.

Why not work the other way... (3, Interesting)

rgbatduke (1231380) | more than 2 years ago | (#37878860)

Every cell phone tower in the US has access to extremely high precision time signals via GPS (and indeed, most of them function as secondary GPS locators by effectively forwarding that signal plus tower location data for phone "GPS" which isn't). Every cell phone tower is basically a big antenna. Every cell phone tower has excellent signal connectivity (usually fiber, sometimes microwave) to a communications network that can carry the signals they receive at any particular frequency, convolved with a universal time reference frequency synchronized by means of the aforementioned GPS, to a large processing station. Hence it is absolutely bone-simple to turn the entire network of existing cell phone towers into one great big radiotelescope.

The cost of doing so is almost certainly going to be a tiny fraction of the cost of building an actual devoted function radiotelescope. I had a student estimate the cost per tower to be in the ballpark of $1000 US for a local computer and sundry electronics, probably less purchased in bulk. One could very likely get the tower owners to donate at least the access to the radio signals (basically costs them nothing), a place to site electronics (ditto), and with luck even a channel and some bandwidth to permit the upload of x-hours of recorded phase locked signal in off-peak bursts as part of their "public service" requirement.

The additional benefit is that one ends up with a radiotelescope that spans a continent -- an aperture several thousand kilometers across, with hundreds of thousands to millions of towers contributing. The resolution would thus be orders of magnitude greater than any of these toys that they are trying to fund and the sensitivity (proportional to N^2) would be MANY orders of magnitude greater as well. In fact, one could probably build arrays that spanned continents and turn the entire surface area of the earth into one big radiofrequency "eye" that can be turned not just anywhere but everywhere 24x7 -- the towers basically record a high resolution hologram of the night sky and one can "look" in any direction you like within any single dataset by simply adjusting the phases of the recorded signals appropriately in the decoding. That is, one doesn't have to devote the towers to looking in some particular direction, one can look in all directions at once and choose what to actually look at in detail in the step where the signals are decoded and recombined with appropriate phase delays.

This will never get funded, of course -- it isn't "big science" in any visible way. Or rather, perhaps it already has been funded, because it is one of the few ways I can think of that one could provide an ABM defense with a universal direction "eye" with sufficient resolution to locate an incoming warhead, and (by using the entire array as a phase-locked TRANSMISSION array) one might even be able to deliver a megawatt or so of power of microwave energy directly onto the missile itself and burn it out. Of course, if this is true then I guess I'll soon have somebody knocking on my door for publishing this on /., but so be it.

rgb

Re:Why not work the other way... (2)

gstrickler (920733) | more than 2 years ago | (#37880014)

You would need to add large, stable, steerable, and extremely sensitive dish near each tower because the cellular antenna and receivers aren't even close to sensitive enough. The RF from the tower would overpower the receiver and electronics for the dish. That's the core of the problem they're trying to address in SA.

Re:Why not work the other way... (1)

rgbatduke (1231380) | more than 2 years ago | (#37886228)

Actually, this is not true. A million towers -- squared. The signal is there, only it is buried in the noise. With one tower you can't extract it. With ten towers (directionally phased) you basically boost the signal to noise ration by 100 (and probably still can't extract it). With a million towers, you increase (directionally selected) signal to noise by a factor of 10^12. That's the whole point of radiotelescope arrays. For small arrays, with only 1000 or so receivers, sure, you need to bump signal to noise some other way, and putting a dish or the like is certainly plausible, but the original radiotelescope array (Jansky's) was indeed just a pair of dipole antennae. Indeed, one part of the proposed SKA is a phased array of simple dipole antennae. It is left as an exercise for the studio audience to note that a significant part of the SKA proposal does indeed spread sparse clusters of these dipoles out across distances up to 3000 km. However, as you note, they are investing a lot more in electronics, installing relatively small numbers of dishes at widely separated sites (and equally small clusters of phased dipoles, ditto), trying to achieve brightness through directionality and amplification with the dishes (although the tiles and dipoles are probably no more sensitive than they would be piggybacked on cell phone towers -- perhaps you didn't realize that a major part of the SKA is these non-dish receivers?)

This is a critical point; no quotidian dish array spread out over only 1 km can even think of touching the resolution of a 3000 to 5000 km array at e.g. the hydrogen line that passes easily through the atmosphere. Tuned to 21 cm, \sin(theta) \approx 2 \times 10^-1 m / 4 \times 10^6 = 5 \times 10^4 radians -- not much compared to big optical telescopes but pretty good as far as peeking through dust clouds. Between trillionfold brightening and 100 microradian resolution, one could take a pretty awesome picture of the sky using e.g. the US, Europe, Australia, Asia as a telescope.

As a side bonus, 1.4 GHz is actually less than computer clocks these days, and with a sub-nanosecond reference one could actually digitize the incoming signal and do all of the image processing in software. Yes, it's big science -- the antennae are relatively cheap, collecting the data per station AT the station is cheap, transmitting the data back to a collection site is moderately expensive, storing there (A million terabytes of storage for order of 1000 seconds of signal from a million receivers) ditto, but the actual image processing would be seriously big computing. OTOH, it could combine building a high-res map of the hydrogen line in the entire 4\pi solid angle with SETI and various other projects all for roughly a $3 billion dollar budget, the same general ballpark as the SKA but with vastly brighter reception in both the dipole and tiled receiver bands.

Even at twice the price IMO it might be worth it. Whether it is "better" than building arrays of dish arrays over a similar baseline -- well, that is a useful question, but the answer is far better at some things, maybe not so much better in others, as one might expect. The dipoles look everywhere at once, the dishes look only at one direction (or one small patch of sky) at a time. I think it is instantly obvious that making all the cell phone towers radiotelescope dipoles (and even adding tiled receivers to them too, why not) yields a continent-spanning array with almost frightfully high resolution and brightness compared to the SKA -- anything the SKA can do the cell-phone tower array can do not just better, but likely a millionfold better, cheaper -- but it may well not be so good at doing some of the things the parabolic dish array will do.

rgb

Re:Why not work the other way... (1)

gstrickler (920733) | more than 2 years ago | (#37887070)

Signal-to-noise ratio. Even with a massive array of dipoles, trying to pick a signal with less than 10^-9 relative strength is essentially impossible. Assuming 32-bit sampling (which is what they're using in state of the art radio astronomy), you've got only a 4B range, and the signals you're looking for a less than 1/1B of that. There isn't enough remaining sensitivity to differentiate it from noise and interference that are thousands, millions, and billions of times stronger. The cellular signals and other earth based ambient RF will so overpower the signals of interest that the data will be useless.

From Parabolic Antenna [wikipedia.org] Applying the above formula to the 25-meter-diameter antennas used by the VLA and VLBA radio telescopes at a wavelength of 21 cm (1.42 GHz, a common radio astronomy frequency) yields an approximate maximum gain of 140,000 times or about 50 dBi (decibels above the isotropic level).

Long dipole antennas [wikipedia.org] also become more directional so you still need a steering mechanism. And since you'll want to observe a particular part of the sky for a while, it will need to be motion compensated star tracking steering mechanism that will increase the cost. An 8WL (8 x 21cm = 1.84m) dipole which has 8.5dBi gain. Compare the 50dBi of a 25m dish and that's 41.5dBi advantage for the dish (yes, I know, comparing a 1.6m dipole to a 25m dish isn't fair, but those are the number I could find). 41.5 dBi is > 2^13 ~ 10,000 times the gain on the 25m dish. Plus, the dish has much better rejection of signals arriving from other directions.

As you noted, 21cm (1.42GHz) is a common radioastronomy frequency. Cellular phones operate at 800-900MHz and 1700-2150MHz, with new frequencies added at 700-800MHz and 2500-2700MHz, all of which bracket 1.42GHz within 1/2 wave length in either direction. Therefore, any antenna with good gain @ 21cm will also have good gain for cellular signals, which will be many billions of times stronger. You can't do the level of RA SKA is intended to do using cellular towers without adding directional antennas, a steering mechanism, a lot of RF shielding, a lot of computing and storage, a whole lot of cost, and a much bigger maintenance problem. Even if you did all those things, you wouldn't be able to pick up the weakest signals unless you use a dish and can shield the cellular RF from the dish, and now you're back to the original problem.

An area of RF quiet significantly improves the S/N ratio. A directional antenna has a huge advantage in that the antenna itself concentrates signals from the direction of interest, and filters those from other directions. You can get by with one or the other for some signals, but for really weak signals, it still won't be enough, even with an array, there simply won't be enough S/N ratio. When you combine those, you have vastly improved S/N ratio.

Re:Why not work the other way... (1)

rgbatduke (1231380) | more than 2 years ago | (#37887260)

Sir, I stand corrected.

rgb

Every cell phone tower is basically a big antenna. (0)

Anonymous Coward | more than 2 years ago | (#37881172)

Really? You just discovered that?

Re:Why not work the other way... (1)

MattskEE (925706) | more than 2 years ago | (#37881784)

This will never get funded, of course -- it isn't "big science" in any visible way

DARPA does love crazy game changing ideas like this... but you'll have a tough time getting this one past a technical review since you appear to be unaware of some serious technical issues.

Every cell phone tower is basically a big antenna.

It really isn't. A cell phone tower is a just a tower with many directional antennas on it. Typically antennas are installed in a trio each one covering 120 degrees, to separate the three "cells" the tower covers. Each antenna has its gain focused on the ground level where the customers are located. The gain straight up will be terrible. Because of this direction you'll be raising the noise temperature of the antenna dramatically because its picking up thermal noise from the hot ground, which will hurt your sensitivity quite a bit.

Then there are issues like sidelobe mitigation (which you can't do since the towers are fixed), radio interference (these are cell phone towers after all), actually getting the phase between multiple towers synchronized (not as easy as you think), the cost will be far higher than your student's guess (you'll need your own RF hardware, the cell phone receivers won't cut it), and the tower operators and antenna operators aren't going to be nearly as accommodating as you assume.

Of course, if this is true then I guess I'll soon have somebody knocking on my door for publishing this on /., but so be it.

I think you'll be fine :-)

Re:Why not work the other way... (1)

rgbatduke (1231380) | more than 2 years ago | (#37886402)

Sure, but all of those issues also exist (except for the radio interference issue, which exists but is smaller) for any array of dipole antennae including the ones that are part of the SKA. However, I wouldn't argue that the cost might be higher than my student's guess -- it was predicated on various things and as you're pointing out, "reality" might be different on some of them, although the idea itself in principle would work with some tweaking.

What I suggested to my student was that he/we write a proposal for a pilot project to see if we could combine just a few -- say, 10 or 100 -- relatively local cell towers into a RT. Even if one ended up designing a very simple dipole unit that could be attached to existing towers at the very top, oriented to receive from straight up and with enough side and bottom screening to eliminate most of the noise from the tower and nearby towers I think it would still be relatively cheap, and the nice thing is (as I said) that you're sitting ON a communications line so all you have to do is record and burst transmit results to postprocess later. With a pilot one could see what works, what doesn't, and determine if the project can be scaled up (even gradually) to compete with the SKA's dipole array at far lower cost. I think it probably can.

rgb

Re:Why not work the other way... (0)

Anonymous Coward | more than 2 years ago | (#37882442)

Hence it is absolutely bone-simple to turn the entire network of existing cell phone towers into one great big radiotelescope.

You're ... exaggerating a bit here. Some problems:

  * GPS isn't accurate enough for timing synchronisation. It gives you precision of a few nanoseconds. You need precision of about 1/20 of the inverse bandwidth: for a bandwidth of 2 GHz (achieved by current radio telescopes), you need to get down to about 0.03 ns. Real radio telescopes have accurate maser clocks, and dedicated connections (not network connections: dedicated fibre, going all the way down to layer one of the OSI model) to distribute the timing signal.

  * Speaking of bandwidth, cell phone towers don't have enough of it. They're designed to receive phone signals across a band of a few MHz, compared to a few GHz for radio telescopes. Sensitivity scales as the square root of bandwidth, so that makes it worse by a factor of ~30.

  * Worse than that: the radio band that cell phone towers are sensitive to is the band which contains phone signals (duh). This means that it's useless because of the interference: a real radio telescope would discard this part of its band.

  * Frequency coverage. The SKA will probably be able to place its band anywhere up to ~30 GHz or so. A cell phone tower's frequency is fixed.

  * System temperature. The receivers of radio telescopes are very carefully built to have as little internal noise as possible. They're usually even cooled with liquid nitrogen or helium, to get the noise down just a bit further. Cell phone tower receivers aren't directed at the sky, so they pick up all the thermal noise from the ground, so there's no point in building them this sensitive: they're built cheap instead.

In addition, here are some ways in which you think this would be an improvement over the SKA, but it wouldn't:

  * Collecting area. A phone tower has an antenna area of a few square metres. The SKA will have a collecting area of a Square Kilometre (from the name). So it'll be the equivalent of hundreds of thousands of phone towers anyway.

  * Budget. At $1000 per phone tower (anyone believe this estimate?), and hundreds of thousands of phone towers, it would cost a similar amount to the SKA anyway.

  * Resolution. You're right: having cell phone towers spread out over an entire continent does give you better resolution. This is why it's also part of the SKA plan: the Australian bid, for example, would have antennas spread out from Western Australia, across to the eastern side of the continent, and to New Zealand.

  * Field of view. Again, you're right that you can look in all directions simultaneously by appropriately combining signals from separate antennae. This is also part of the SKA design, with the low-frequency aperture arrays: similar to those used by current telescopes such as the MWA and LOFAR.

There are probably other issues: this is just off the top of my head.

Re:Why not work the other way... (2)

hyperfine transition (869239) | more than 2 years ago | (#37884568)

GPS does not provide a good enough time reference for an application like this. Typically you need a hydrogen maser; these cost about $300K. The problem is that GPS has pretty poor short term stability - about +- 20 ns at 1 s for a low cost timing receiver. Averaged over one day GPS gives you a decent frequency reference but to average, you need another oscillator like a rubidium atomic clock. The rubidium gives you better short term stability and then you improve its long term stability by comparing it with GPS and adjusting it. But a rubidium isn't good enough either for the application. Providing suitable timing references to a distributed system is an active area of research. The paper "Phase transfer ..." http://www.skatelescope.org/publications/ [skatelescope.org] gives you an idea of the timing requirements.

Re:Why not work the other way... (1)

rgbatduke (1231380) | more than 2 years ago | (#37886566)

Well, OK then. Yes, stability is key, although I fail to completely understand why they don't put high precision and stable clocks in the GPS satellites if they are going to put it anywhere, since putting a $300K clock at every tower would, no doubt, raise the cost a bit...;-)

rgb

Re:Why not work the other way... (1)

hyperfine transition (869239) | more than 2 years ago | (#37904784)

Not quite sure what you're saying. GPS satellites do have good clocks on board - rubidium and cesium atomic clocks - and these clocks are steered from the ground by a very large ensemble of atomic clocks including hydrogen masers. The proBlem is transferring this to a ground station. The ionosphere and troposphere introduce short term noise that degrades timing references that you can derive from GPS. GPS broadcasts information that allows correction for these effects but this is of course via a model. You can average out some of the residual noise but you then want a good oscillator to flywheel on. The end result is an oscillator that is good to about 1 part in 10^12. CDMA base stations typically used to have a GPSDO ie a GPS receiver disciplining a rubidium or good quartz clock because of timing and holdover (how long you can run if GPS signals are lost) requirements. Disclaimer: I may or may not be working on a project connected with the SKA :-)

Re:Why not work the other way... (1)

hyperfine transition (869239) | more than 2 years ago | (#37904806)

Oops, now I see what you meant. When I said that GPS was not good enough for this application, I was referring to VLBI, not synchronizing a phone network.

Re:Why not work the other way... (1)

rgbatduke (1231380) | more than 2 years ago | (#37915420)

Yes, well I have given up -- you and others do indeed seem to have thought things through more carefully than I have so far, which is to be expected I suppose but it's disappointing that it won't quite work, if only because it would make such a hell of an array if it did. But between clock problems and signal problems, looks like it almost only counts with hydrogen bombs and hand grenades, not cell phone tower radiotelescopes. Sigh. Hope I wasn't too obnoxious in my misdirected enthusiasm...;-)

rgb

What is the big deal? (1)

technoslash (2496310) | more than 2 years ago | (#37880278)

I am not quite sure how this will influence the bid? It seems to be yet another PR attempt to try and convince the uninformed of the benefits of a R2m investment in SKA SA and MeerKAT.

Re:What is the big deal? (1)

bruce_the_loon (856617) | more than 2 years ago | (#37880372)

It is useful because it will eliminate a possible source of interference at the Karoo site that isn't present at the Australian site without shutting cellular phones down over a too-wide area.

And do I sense hostility for our country getting the SKA or are you merely annoyed at having to convince the ignorant of its obvious benefits?

Re:What is the big deal? (1)

technoslash (2496310) | more than 2 years ago | (#37880728)

If those guys have come up with a technology that will eliminate the interference, I would be really impressed. I can't imagine they will get more than 30-40dB down from the "omnidirectional" base station antennas. MeerKAT (let alone the SKA) will be an extremely sensitive instrument, able to "detect a cell phone on the moon", so maybe you wont saturate your receivers, but you always going to see and will always need to deal with it if you going to be looking comic signatures in your mobile bands. I think the SKA is a great project and hosting it in Africa would be great for national pride. However I am yet to see a technical thesis on the clear social economic benefits of hosting a large radio telescope in Africa. Unfortunately I have only heard the bold claims of a few science academics and politicians; (which have been rather amusing); no hard facts. It may have been better to simply invest in the communication infrastructure and focus our efforts on developing solutions for green energy. Now that has "obvious" benefits.

Re:What is the big deal? (1)

EETech1 (1179269) | more than 2 years ago | (#37884166)

Somebody Please!

calculate how far away (skyward) the SKA could actually hear a GSM phone!

Probably way past the moon, but I could be guessing...

Thanks!

Coal seam gas exploration at SKA site (0)

Anonymous Coward | more than 2 years ago | (#37881068)

SKA will have to accommodate the rights of the miners to just walk in and start drilling, in aus you don't own your land.

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