Re: And yet an even more radical proposal.
From: Jan Panteltje (pNaonStpealmtje_at_yahoo.com)
Date: 02/21/05
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Date: Mon, 21 Feb 2005 22:08:16 GMT
On a sunny day (21 Feb 2005 12:24:20 -0800) it happened "Robert Clark"
<rgregoryclark@yahoo.com> wrote in
<1109017460.434188.272970@f14g2000cwb.googlegroups.com>:
>Another possible problem is that I'm not even sure the receivers that
>come with the satellite dishes can even detect frequencies other than
>the 12 Ghz the satellites broadcast at.
> In regard to the wavelengths that the .5 m antennas could usefully
>collect, I've seen references that a dipole antenna should be a quarter
>of the wavelength. Is this different for parabolic antennas?
> I'm thinking perhaps you could simply attach flat metal dipoles to the
>surface of the .5 meter antennas so they could collect megahertz
>frequencies. Then at a quarter wavelength you could collect down to 2
>meter wavelengths or 150 Mhz.
> While we're at it, the thought of using dipoles, like TV antennas,
>raises another possibility. You need receivers for these frequencies.
>Where could we get large numbers of receivers already existing at these
>frequencies? Inside TV's! Assuming we could solve the problem of
>tranmitting the data to a central site (ultra wideband, broadband over
>power-lines, amateur packet radio, etc.), we could have all new TV's
>come installed with a circuit that transmits received signals to the
>central site. The number of new TV's sold yearly worldwidde is 90
>million. This would result in markedly larger numbers of possible
>receivers even above the satellite TV approach.
> There might be privacy issues with this idea however.
>
>
> Bob Clark
>
>
>Robert Clark wrote:
>> A.) According to this article $1.4 billion dollars is earmarked to be
>> spent on the Square Kilometer array with completion expected by 2015:
>>
>> Radio Astronomy Will Get a Boost With the Square Kilometer Array.
>>
>http://www.universetoday.com/am/publish/radio_astronomy_boost_ska.html?1592004
>>
>> As I stated below the primary extra components to be added to the
>> DirecTV dishes to be used for radio astronomy are the feedhorn and
>the
>> preamp. The feedhorn is simply a metal pipe of little cost. The
>> SetiLeague site lists sellers of specially made preamps for SETI
>> search at $150. But these are handmade. From the low number of
>circuit
>> elements, I estimate that if mass produced at the millions of items
>> level the price could come down in the range of $10 each.
>> This site states the rate of growth of satellite TV subscribers is
>at
>> 4 million per year:
>>
>> Satellite TV Basics.
>> http://www.satellitetv-hq.com/hqguides/satellite-tv-basics.html
>>
>> This means the *receivers* for the SKA system if using these
>> satellite dishes could be installed in 1 year at an extra cost of $10
>> x 4,000,000 = $40 million dollars. Note that the feedhorn and the
>> preamp could be attached at manufacture would not cost more on
>> installation labor. The installation is already paid for by the
>> satellite TV subscribers. To pay for the extra cost for the added
>> equipment you could simply add $1 extra per month to the subscriber
>> rate. Then these 4 million, .5 meter wide dishes would have a total
>> collecting area of a disk 2000 x .5 m = 1000m = 1km wide, the total
>> collecting area expected for the SKA. Moreover this would have the
>> advantage that an additional square kilometer of collecting area
>would
>> automatically be added every year over several years going by the
>> present growth rate.
>> You could also attach the extra equipment to the 25 million
>satellite
>> systems already installed in perhaps 4 or 5 years. The number of
>> satellite TV subscribers worldwide was 60 million in 2003 and is
>> expected to grow to 100 million by 2008:
>>
>> Digital Satellite TV Platforms Continue to Gain Subscribers, and
>> Profits are on the Rise.
>> http://www.instat.com/press.asp?ID=1171&sku=IN0401236MB
>>
>> If this many .5 meter antennas were networked together, they would
>> have the collecting area of a single antenna 10,000 x .5 m = 5 km
>> wide.
>>
>> Note that the idea of using over 50 million separate, stationary
>> elements is one of the proposals being considered for the SKA
>> architecture:
>>
>> Aperture Array (AA)
>> http://www.skatelescope.org/pages/design_nl.htm
>>
>> This method of keeping the receiving antennas fixed while detection
>> directions are determined electronically is called the phased array
>> approach and has the advantage that many separate targets can be
>> observed simultaneously. It also has the advantage that interfering
>> local signals can be suppressed. However, the Aperture Array has
>> antennas close together in a predetermined configuration with the
>> positions precisely determined. How could this work for the randomly
>> positioned satellite dishes?
>> Methods of differential GPS and carrier phase synthesis now have the
>> capability of determining position to within millimeters. The method
>> compares the GPS signal between a precisely known site and an unknown
>> site to locate the unknown site to within centimeters. Then a
>> comparison is made in the actual phase of the signals received at the
>> two sites to locate the unknown site to within millimeters:
>>
>> CARRIER-PHASE TRACKING
>> "Carrier-phase tracking provides for a more accurate range resolution
>> due to the short wavelength (about 19 centimeters for L1 and 24
>> centimeters for L2) and the ability of a receiver to resolve the
>> carrier phase down to about 2 millimeters. This technique has primary
>> application to engineering, topographic, and geodetic surveying and
>> may be employed with either static or kinematic surveys. There are
>> several techniques that use the carrier phase to determine a
>station's
>> position. These include static, rapid-static, kinematic, stop-and-go
>> kinematic, pseudokinematic, and on-the-fly (OTF) kinematic/Table 8-4
>> lists these techniques and their required components, applications,
>> and accuracies."
>> http://cartome.org/FM3-34/Chapter8.htm
>>
>> This should be sufficient for keeping the signals for the millions
>of
>> antennas in phase up to perhaps 3 cm wavelength, 10 Ghz frequency.
>> Timing synchronization can be obtained by synchronizing from the
>> common signal received by the dishes from the satellite.
>> The Argus telescope at Ohio State University (this is different from
>> Project Argus operated by The Seti League) may provide a model for
>how
>> sensitive such a system can be operating from noisy populated areas:
>>
>> Newsgroups: sci.astro.seti
>> From: Bob Dixon <dixo...@osu.edu>
>> Date: Wed, 19 May 2004 12:49:02 -0400
>> Subject: The Argus Telescope
>>
>http://groups-beta.google.com/group/sci.astro.seti/browse_frm/thread/54ddf1f29f629f20/
>>
>> Argus Expands the Search For Life.
>> By Daniel Sorid
>> posted: 03:30 pm ET
>> 09 June 2000
>> http://www.space.com/searchforlife/seti_argus_000609.html
>>
>> Note though that the continent wide satellite dish system will have
>> an advantage over Argus in dismissing unwanted signals in that such
>> signals would only be detected by a local group of antennas not the
>> continent wide system.
>>
>> In mentioning an estimated price for this system, I emphasized the
>> estimate was for the *receiving* part of the system. But of course
>for
>> such a system of separate receivers, it is just as important to
>> combine and process the signals.
>> In the thread for DirecTV being used for SETI, someone mentioned you
>> might need to transfer 1 Gbps from each antenna for detections at 12
>> Ghz. I seem to recall that analog signals can be tranferred in
>greater
>> density than digital signals. Perhaps the signal received by each
>> antenna can be transmitted in analog form with a stamp indicating its
>> location and time of origin.
>> For examples of the data density required we could look at some
>> examples of systems of separate antennas that have been used to give
>> combined signals in *real time*:
>>
>> Astronomers Demonstrate a Global Internet Telescope.
>> Date Released: Friday, October 08, 2004.
>> http://www.spaceref.com/news/viewpr.html?pid=15251
>>
>> This produced data of 32 Mbits/second for each telescope for
>> observations at 1.6 Ghz. So at 16 Ghz perhaps 320 Mbps might be
>> expected for each antenna. The data was sent over a high-speed
>> internet network available to universities that operates at gigabits
>> per second. Within a few years, the data transfer rate is expected to
>> reach tens of gigabits per second.
>>
>> And:
>>
>> Prototype SETI Antenna Array Will Help Radio Astronomers Too.
>> Date Released: Wednesday, June 07, 2000.
>> http://www.spaceref.com/news/viewpr.html?pid=1992
>>
>> This is of the Argus telescope at Ohio State University. The 64
>> antennas here detect signals from 400 to 2000 Mhz. The antennas
>> together produce 2.56 gigabytes per second, or 20.48 gigabits per
>> second. So each telescope produces 320 Mbps. This article states that
>> no physical connection could economically carry that much data over
>> distance however this was written in 2000. Ultra wideband technology
>> (mentioned below) now has that capability.
>>
>> For processing the data for the proposed SKA system, I expect the
>> distributed computing system used by Set@Home to be used, wherein
>> millions of computers take part in the calculations. As for how the
>> data can be sent by the individual antennas, there are a few possible
>> ways the signals could be combined.
>>
>> 1.)DirecTV offers a two-way broadband satellite internet service
>> called DirecWay. This allows signals to be sent from the home
>antennas
>> back up to the transmitting satellite. However, this system currently
>> has only a 100,000 subscribers in place. I want to use the millions
>of
>> subscribers using the satellite TV systems. I think a minor low-cost
>> modification of the current TV antennas would also allow them to
>> transmit to the satellites used for broadband internet service. (I
>> don't think the satellites used for TV service can be used to receive
>> signals.)
>>
>> 2.)Another possibility for transferring the data from each antenna
>> might be to use military satellites currently used for surveillance
>on
>> radio transmissions, perhaps using satellites that were
>decommissioned
>> and are no longer used for sensitive military tasks.
>>
>> 3.)Possibly the techniques used with amateur packet radio could be
>> used. Here radio links are used to setup data networks analogously to
>> how the internet sets up data transfer networks using the TCP/IP
>> protocols:
>>
>> N6GN's Microwave Link Page
>> http://www.sonic.net/~n6gn/uwavelink/uwv.html
>>
>> INEXPENSIVE MULTI-MEGABAUD MICROWAVE DATA LINK
>> http://www.sonic.net/~n6gn/hr89/uwvarticle.html
>>
>> 4.)Ultra wideband (UWB) promises gigabit data transfers over both
>> cable and wireless connections and should be available this year
>> (2005):
>>
>> New chipset promises gigabit broadband on cable and wireless.
>> Rupert Goodwins
>> ZDNet UK
>> May 11, 2004, 15:20 GMT
>> http://news.zdnet.co.uk/communications/0,39020336,39154271,00.htm
>>
>> Ultrawideband in 2005, but only in America
>> Rupert Goodwins
>> ZDNet UK
>> February 19, 2004, 09:45 GMT
>>
>http://news.zdnet.co.uk/communications/wireless/0,39020348,39146644,00.htm
>>
>> Ultrawideband: Wireless Whoopee.
>> 08:34 AM Oct. 09, 2004 PT
>> "SAN FRANCISCO -- Think of it as Wi-Fi on steroids. On its way to
>U.S.
>> living rooms and maybe even automobiles is a new type of high-speed
>> wireless connection that promises downloaded data rates of up to 1
>> gigabit per second -- roughly 18.5 times the speed of Wi-Fi -- to
>> personal computers and other devices.
>> "This ultrawideband technology, which could become available in the
>> next two years, also allows the devices to send data upstream to a
>> network at 480 megabits per second."
>>
>http://www.wired.com/news/technology/0,1282,65297,00.html?tw=wn_tophead_3
>>
>> 5.)Some public utilities now collect their meter readings from radio
>> transmitters attached to their meters. The data is collected by
>> receiver on utility poles and then transmitted to a central site.
>This
>> method could be adapted to work for collecting the data from the
>> separate antennas.
>>
>> 6.) The above methods would require that the data transmissions be on
>> specified frequencies that will not be used for detections. However,
>> another method might not have this limitation:
>>
>> Broadband Over Power Lines?
>> 01:15 PM Feb. 09, 2003 PT
>> "ST. LOUIS -- Coming to a home or office near you could be an
>electric
>> Internet: high-speed Web access via ubiquitous power lines, of all
>> things, making every electrical outlet an always-on Web connection."
>> http://www.wired.com/news/technology/0,1282,57605,00.html
>>
>> This is a new technique already being tested in small markets to
>> provide interent service over power lines. The speed of transmission
>> can be ramped up to 1 gigabits per second using ulta wideband
>> technology.
>>
>> B.)This last leads me to another proposal for large scale separated
>> antennas for radio astronomy: using the electrical wiring in
>> households as radio antennas. Here's a post to
>> rec.radio.amateur.antenna discussing this:
>>
>>
>==========================================================================
>> From: Ed Hare, W1RFI (w1rfi@arrl.net)
>> Subject: Re: ISO info about using house wiring as a TV antenna
>> Newsgroups: rec.radio.amateur.antenna
>> Date: 2000-12-29 15:33:06 PST
>>
>> Richard Friday <tgirwf@bigfoot.com> wrote in message
>> news:92j4h7$2b2$1@bob.news.rcn.net...
>>
>> > I know this post might be off-topic but could find no other
>newsgroup that
>> > had "antenna" in its name. I'd be most appreciative if someone
>could point
>> > to a more suitable discussion or other source of information.
>> > I've seen advertised a device that claims to allow you to use the
>> > electrical wiring of your house as a tv antenna. You plug this
>device
>> > into an outlet, and then use connections it provides as your tv
>antenna.
>> > I'm trying to find out if this actually works but have not been
>able to
>> > find any reviews.
>>
>> This device will receive some signals. However, house electrical
>> wiring is
>> not a very good VHF antenna system for a couple of reasons:
>>
>> First, it is very difficult to predict the direction that the house
>> wiring
>> will best receive from. It is quite likely that the antenna pattern
>> will
>> have all sorts of peaks and nulls, sort of as if you had a rotatable
>> TV
>> antenna that was pointing in several directions at once. This may
>not
>> pick
>> up much of the TV signal you want to pick up or may have multiple
>> responses,
>> resulting in ghosts.
>>
>> Also, an electrical power line can be a very noisy place. All sorts
>of
>> electronic devices on the line, from power-line equipment itself to
>> every
>> motor or power supply plugged in near you may create noise that will
>> interfere with the signal you want to receive.
>>
>> If you have no other antenna choice, that device may be useable, but
>I
>> don't
>> think it will work as well as a good set of "rabbit ears" on top of
>> your TV.
>>
>> Ed Hare, W1RFI
>>
>==========================================================================
>>
>> The disadvantage of the electrical wiring going in several different
>> directions may actually be an advantage in regards to a SETI search
>> since you would want the detections to be omnidirectional. If there
>> are 100,000,000 homes which average 10 meters across then this would
>> result in a collecting area of 10,000 x 10 meters = 100 km across.
>> Since you would want to include large commercial establishments, the
>> size would actually be larger than this.
>>
>>
>>
>> Bob Clark
>>
>>
>> rgregoryclark@yahoo.com wrote in message
>news:<1106126272.160248.294240@z14g2000cwz.googlegroups.com>...
>> > I was interested to read this on the Seti League web site:
>> >
>> > __________________________________________________________
>> > Parasitic SETI
>> > Dear Dr. SETI:
>> > As a Satellite dish owner and a strong interest in SETI, I was
>> > wondering if anything is available to allow the home satellite dish
>> > owner to 'search' when he is not watching TV. I do a bit of
>programing
>> > and would love to help make it so home dish owners could do this.
>Is it
>> > possible? What would it take? Does the dish have to follow a spot
>or
>> > can it sweep the sky from a fixed position? If this is possible it
>> > could add a million listeners to the system.
>> >
>> > Bill T.
>> >
>> > The Doctor Responds:
>> > Absolutely, Bill! Parasitic SETI with a home satellite TV dish is
>not
>> > only feasilble, it's widely practiced. A second feedhorn and preamp
>> > assembly are mounted next to the C-band horn/LNB at the apex of the
>> > dish (see Figure 2 of this article). This assembly feeds the rest
>of a
>> > SETI system (see our online Tech Manual). You can then sweep out
>the
>> > sky, as described here. And yes, a million participants would be
>nice,
>> > but our goal is a more modest 5000 stations.
>> > __________________________________________________________
>> > http://www.setileague.org/askdr/parasite.htm
>> >
>> > I believe they are referring to the 6 ft. backyard type antennas,
>> > judging from the linked images on the page. But could the roof
>mounted
>> > DirectTV and Dish Network type antennas be used for SETI?
>> > The mentioned extra equipment are an extra feedhorn and a
>> > preamplifier. The feedhorn can made cheaply but the preamp seems
>> > expensive. If these preamps were mass produced for this purpose
>could
>> > their per item cost be brought under $50?
>> > I'm envisionig a government agency such as NSF, or a scientically
>> > interested billionaire, paying satellite TV companies to attach
>this
>> > extra equipment to their satellite dishes. Say $100 million is
>> > earmarked for the program. Then you would want the extra cost to be
>> > under $100 for each dish for say 1,000,000 subscribers. Judging
>from
>> > the diagram in the online Tech Manual linked to on the page, the
>other
>> > equipment should be doable by the equipment that comes with the
>> > satellite TV system. Computer processing would be done separately
>at a
>> > central location.
>> > If you had a 1,000,000 of these .5 meter wide antennas it would
>have
>> > the detection sensitivy of a single antenna 500 meters wide.
>> > Bob Clark
>
I am just a humkble electronics person with several years experience with
sat dishes.. and software (I write).
2 things bother me about the proposal (topic)
1)
The smaller the dish, the worse the signal to noise (lower signal level),
and you mostly will be in the noise.
2)
polarization, sat dish LNBs come hor or vert polarized, and perhaps circular.
What will it be.
If you only use the dish and your own preammp what will it be made of?
10 Ghz = 3 cm wavelength.
Remember the dishes are used to receive from only 40000km or a little more
away, and then get 'acceptable' signal to noise.
The sats transmits several watts of power.
For astronomy you will likely want to be a few orders of magnitude more
sensitive.
Liquid cooled parametric preamps for the amateur?
What am I missing here?
- Next message: Timo Nieminen: "Re: Is electromagnetic field theory unified?"
- Previous message: Paul Holbach: "Re: Existence of mathematical entities (Re: Successor Axiom: on what grounds TF?)"
- In reply to: Robert Clark: "And yet an even more radical proposal."
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