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Can DirectTV-type satellite dishes be used for SETI?
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 |
#3
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Somebody's having a laugh, surely? A satellite dish is about a million times
smaller. "Scott" wrote in message ... Now I'm confused. The thread title asks about DirecTV dishes, then in the post it is mentioned about sweeping the dish across the sky and the answerer mentions C Band. DirecTV dishes ordinarily are not set up to "sweep" across the sky, nor are they operating at C Band. So, is anybody using DirecTV dishes for SETI work? If old C Band stuff can be used for SETI listening, that would be great since (at least around me) there are many old C Band setups unused in yards these days. Many could probably be had for free to anyone who would be willing to removed the big old ugly beasts from back yards. Scott N0EDV wrote: 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 |
#4
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wrote in message oups.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 Since it is quite clear that a dish is used for highly directional communication, and SETII stands for Search for Extra Terrestrial INTELLIGENCE by IDIOTS.... Androcles. |
#5
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wrote:
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? Sure, they'd work. The dishes are smaller (1 ft diameter or so) but the same principles apply as for the larger dishes (8-12 ft). The only thing is that you'd need to work at much higher frequencies. You'd need to do SETI at the 12GHz band. Al 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 |
#6
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wrote:
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. [snip] 1) What is the diameter of a home satellite dish? What is the diameter of the Aricebo dish? Intercepted amplitude varies as the square of that ratio. 2) What is the temperature of a home satellite dish amplifier? What is the temperature of the Aricebo first amplifier? -- Uncle Al http://www.mazepath.com/uncleal/ (Toxic URL! Unsafe for children and most mammals) http://www.mazepath.com/uncleal/qz.pdf |
#7
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a question, in order to use all the "civilian" dishes as an array they
should be placed in a predetermined shape right? |
#8
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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? Sure, they'd work. The dishes are smaller (1 ft diameter or so) but the same principles apply as for the larger dishes (8-12 ft). The only thing is that you'd need to work at much higher frequencies. You'd need to do SETI at the 12GHz band. Al only problem is the signal loss, the 1/(d^2) loss from alien planet to Earth assuming you keep your antenna directly pointed at his for at least 15 min(rather difficult since neither know where the other is). If he is 20 light years away, or about 1 E+13 miles away the signal loss is about -400 dB (at C band) What this means is that the alien will have to convert a small moon completely into microwave energy pointed towards earth. I doubt the aliens could get funding to do it, because they would have to choose a direction to aim their 1/10 degree beam too. Listening is the low cost EZ part. If SETI was really serious they would be building a huge microwave transmitter. |
#9
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"k3ym4st3r" wrote in message oups.com... a question, in order to use all the "civilian" dishes as an array they should be placed in a predetermined shape right? no they have to be phased though. So the received signal adds in phase from all the dishes. That is what the big arrays do. |
#10
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k3ym4st3r wrote:
a question, in order to use all the "civilian" dishes as an array they should be placed in a predetermined shape right? You can choose your shape and suffer the resulting sidelobes. But you do have to determine and compensate for the baseline geometry to within fractions of a wavelength. All the signals from the target must add in phase if you are to get any benefit from using multiple aerials. This is non trivial if you want to track a celestial object across the sky. A large phased array at low frequencies discovered the first pulsar. You will need a few acres of toy dishes dedicated to the task to stand any chance at all. Try the sun and Jupiter instead - you should see them OK. Regards, Martin Brown |
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