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What is the highest radio frequency used for radio astronomy?
Hi:
What is the highest radio frequency used for radio astronomy? According to the link below, it is 3438 GHz: http://books.nap.edu/openbook.php?re...=11719&page=11 Is 3438 GHz the highest radio frequency used for radio astronomy? Thanks, Radium |
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What is the highest radio frequency used for radio astronomy?
Radium wrote:
Hi: What is the highest radio frequency used for radio astronomy? According to the link below, it is 3438 GHz: http://books.nap.edu/openbook.php?re...=11719&page=11 Is 3438 GHz the highest radio frequency used for radio astronomy? If you read on a little farther you'll find 'blurring the distinction between radio astronomy and infrared astronomy.' So where do you want to draw the line between radio astronomy and infrared astronomy? There's you're answer. |
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What is the highest radio frequency used for radio astronomy?
So where do you want to draw the line between radio astronomy and
infrared astronomy? There's you're answer. Why don't you just call it all electromagnetic astronomy? |
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What is the highest radio frequency used for radio astronomy?
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What is the highest radio frequency used for radio astronomy?
In sci.astro.amateur gwatts wrote:
Radium wrote: Hi: What is the highest radio frequency used for radio astronomy? According to the link below, it is 3438 GHz: http://books.nap.edu/openbook.php?re...=11719&page=11 Is 3438 GHz the highest radio frequency used for radio astronomy? If you read on a little farther you'll find 'blurring the distinction between radio astronomy and infrared astronomy.' So where do you want to draw the line between radio astronomy and infrared astronomy? There's you're answer. Hi, Radium, gwatts, and all. I'd agree that the real question here may be where to draw the line between radio and infrared, and thus between radio astronomy and infrared astronomy. What I learned about 40 years ago was that while the line wasn't a clear one, the shortest or highest-frequency range of radio waves traditionally placed in that classification were "millimeter waves" with a wavelength of 1-10mm. Given that the speed of light, c, is very close to 3 x 10^10 centimeters per second, so that a 1 cm or 10mm wave would have a frequency of around 30 Gz, this category (also known as Extremely High Frequency or EHF) has a 30-300GHz range. A frequency of 3438 GHz, with a wavelength a bit shorter than 100 microns, would thus be about an order of magnitude higher in frequency than the top of the EHF range. While I'm not sure if there's a specific technical name for this range (analogous to the various categories of radio waves like EHF), my first layperson's guess would be that it could be considered very far infrared (that is, far from the visual spectrum and close to radio). It's interesting question how radio and infrared astronomy are distinguished: mainly by the nature of the waves, or also by the apparatus used. I'd like to to learn more of this myself. Again, I'd emphasize that in giving the range for EHF, I'm not saying that anything above 300 GHz wouldn't be considered radio, only mentioning this category as an example of what was traditionally considered near the top of the radio spectrum. Maybe Laura or others could comment more expertly on this. Most appreciatively, Margo Schulter Lat. 38.566 Long. -121.430 |
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What is the highest radio frequency used for radio astronomy?
"Margo Schulter" wrote in message ... In sci.astro.amateur gwatts wrote: Radium wrote: Hi: What is the highest radio frequency used for radio astronomy? According to the link below, it is 3438 GHz: http://books.nap.edu/openbook.php?re...=11719&page=11 Is 3438 GHz the highest radio frequency used for radio astronomy? If you read on a little farther you'll find 'blurring the distinction between radio astronomy and infrared astronomy.' So where do you want to draw the line between radio astronomy and infrared astronomy? There's you're answer. Hi, Radium, gwatts, and all. I'd agree that the real question here may be where to draw the line between radio and infrared, and thus between radio astronomy and infrared astronomy. What I learned about 40 years ago was that while the line wasn't a clear one, the shortest or highest-frequency range of radio waves traditionally placed in that classification were "millimeter waves" with a wavelength of 1-10mm. Given that the speed of light, c, is very close to 3 x 10^10 centimeters per second, so that a 1 cm or 10mm wave would have a frequency of around 30 Gz, this category (also known as Extremely High Frequency or EHF) has a 30-300GHz range. A frequency of 3438 GHz, with a wavelength a bit shorter than 100 microns, would thus be about an order of magnitude higher in frequency than the top of the EHF range. While I'm not sure if there's a specific technical name for this range (analogous to the various categories of radio waves like EHF), my first layperson's guess would be that it could be considered very far infrared (that is, far from the visual spectrum and close to radio). It's interesting question how radio and infrared astronomy are distinguished: mainly by the nature of the waves, or also by the apparatus used. I'd like to to learn more of this myself. Again, I'd emphasize that in giving the range for EHF, I'm not saying that anything above 300 GHz wouldn't be considered radio, only mentioning this category as an example of what was traditionally considered near the top of the radio spectrum. Maybe Laura or others could comment more expertly on this. Most appreciatively, Margo Schulter Lat. 38.566 Long. -121.430 So its your contention that the atmosphere is transparent all the way up from microwaves to IR? |
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What is the highest radio frequency used for radio astronomy?
On Aug 30, 10:34 am, "Peter Webb"
wrote: "Margo Schulter" wrote in message ... In sci.astro.amateur gwatts wrote: Radium wrote: Hi: What is the highest radio frequency used for radio astronomy? According to the link below, it is 3438 GHz: http://books.nap.edu/openbook.php?re...=11719&page=11 Is 3438 GHz the highest radio frequency used for radio astronomy? If you read on a little farther you'll find 'blurring the distinction between radio astronomy and infrared astronomy.' So where do you want to draw the line between radio astronomy and infrared astronomy? There's you're answer. Hi, Radium, gwatts, and all. I'd agree that the real question here may be where to draw the line between radio and infrared, and thus between radio astronomy and infrared astronomy. What I learned about 40 years ago was that while the line wasn't a clear one, the shortest or highest-frequency range of radio waves traditionally placed in that classification were "millimeter waves" with a wavelength of 1-10mm. Given that the speed of light, c, is very close to 3 x 10^10 centimeters per second, so that a 1 cm or 10mm wave would have a frequency of around 30 Gz, this category (also known as Extremely High Frequency or EHF) has a 30-300GHz range. A frequency of 3438 GHz, with a wavelength a bit shorter than 100 microns, would thus be about an order of magnitude higher in frequency than the top of the EHF range. While I'm not sure if there's a specific technical name for this range (analogous to the various categories of radio waves like EHF), my first layperson's guess would be that it could be considered very far infrared (that is, far from the visual spectrum and close to radio). It's interesting question how radio and infrared astronomy are distinguished: mainly by the nature of the waves, or also by the apparatus used. I'd like to to learn more of this myself. Again, I'd emphasize that in giving the range for EHF, I'm not saying that anything above 300 GHz wouldn't be considered radio, only mentioning this category as an example of what was traditionally considered near the top of the radio spectrum. Maybe Laura or others could comment more expertly on this. Most appreciatively, Margo Schulter Lat. 38.566 Long. -121.430 So its your contention that the atmosphere is transparent all the way up from microwaves to IR? Nobody limited the discussion to *terrestrial* astronomy. If one is working from space, the transparency of the atmosphere is irrelevant. Austin |
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What is the highest radio frequency used for radio astronomy?
Peter Webb wrote:
.... So its your contention that the atmosphere is transparent all the way up from microwaves to IR? I didn't see anything referring to atmospheric transparency in Ms. Schulter's response but I'll point you to http://www.alma.nrao.edu/memos/html-...7/memo187.html or 'MMA Memo 187: Modeling of the Submillimeter Opacity on Chajnantor' specifically figures 1-6 which show opacities through air paths and modeled opacities over Mauna Kea, HI. Farther on the authors discuss predicting opacities over the ALMA site in Chile. What it comes down to is: No, the atmosphere is not 'transparent all the way up from microwaves to IR,' but there are windows of transparency where valuable observations can be made. Something else possibly worth perusing is http://www.cv.nrao.edu/naasc/present...07_Handout.pdf and of course the entire ALMA/MMA Memo Series, http://www.alma.info/ |
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What is the highest radio frequency used for radio astronomy?
"Peter Webb" wrote in message ... "Margo Schulter" wrote in message ... In sci.astro.amateur gwatts wrote: Radium wrote: Hi: What is the highest radio frequency used for radio astronomy? According to the link below, it is 3438 GHz: http://books.nap.edu/openbook.php?re...=11719&page=11 Is 3438 GHz the highest radio frequency used for radio astronomy? .... in frequency than the top of the EHF range. While I'm not sure if there's a specific technical name for this range (analogous to the various categories of radio waves like EHF), my first layperson's guess would be that it could be considered very far infrared (that is, far from the visual spectrum and close to radio). http://en.wikipedia.org/wiki/Electromagnetic_spectrum 3.4THz would be well into the far infra-red. It's interesting question how radio and infrared astronomy are distinguished: mainly by the nature of the waves, or also by the apparatus used. I'd like to to learn more of this myself. Again, I'd emphasize that in giving the range for EHF, I'm not saying that anything above 300 GHz wouldn't be considered radio, only mentioning this category as an example of what was traditionally considered near the top of the radio spectrum. .... So its your contention that the atmosphere is transparent all the way up from microwaves to IR? I don't believe Margo suggested that at all. This page lists some of the sources of line features in that region: http://kp12m.as.arizona.edu/docs/wha...millimeter.htm George |
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What is the highest radio frequency used for radio astronomy?
On Aug 30, 8:03 am, Margo Schulter wrote:
It's interesting question how radio and infrared astronomy are distinguished: mainly by the nature of the waves, or also by the apparatus used. I'd like to to learn more of this myself. Again, I'd emphasize that in giving the range for EHF, I'm not saying that anything above 300 GHz wouldn't be considered radio, only mentioning this category as an example of what was traditionally considered near the top of the radio spectrum. Maybe Laura or others could comment more expertly on this. The ITU definition of "radio" ends at the top of EHF, at 300 GHz. However, this is more a reflection of the technical state of the art at the time the definition was made. Earlier definitions ended at 30 GHz, or even lower. I've read papers in journals for radio equipment that operates above 400 GHz. You need a microscope to inspect the components. :-) Above 300 GHz is no man's land, in that no radio license is required to send signals. Laser communication links are not licensed as radios; they are not generally licensed at all, unless health & safety officials take an interest in the lasers themselves. The spectrum between EHF and infrared is viewed as not useful for communication, because the atmosphere is more-or-less opaque at these wavelengths. But that's what they said about frequencies about 30 MHz in the 1920s, too. And in space, who cares? The usual agreement is that it's radio astronomy when the incoming signals are electronically detected (e.g. diodes) and processed. It's optical/infrared astronomy when the incoming signals are measured by a bolometer or other non-electronic means. There is, naturally, some crossover. Laura Halliday VE7LDH "Non sequitur. Your ACKS are Grid: CN89mg uncoordinated." ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer |
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