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What is the highest radio frequency used for radio astronomy?



 
 
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  #1  
Old August 30th 07, 08:33 AM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Radium[_2_]
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Posts: 109
Default 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

  #2  
Old August 30th 07, 12:33 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
gwatts
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Posts: 9
Default 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.
  #3  
Old August 30th 07, 01:51 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
[email protected]
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Default 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?

  #4  
Old August 30th 07, 01:56 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
gwatts
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Posts: 9
Default What is the highest radio frequency used for radio astronomy?

wrote:
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?


It's not my call.
  #5  
Old August 30th 07, 04:03 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Margo Schulter
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Posts: 304
Default 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

  #6  
Old August 30th 07, 04:34 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Peter Webb[_2_]
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Posts: 927
Default 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?


  #7  
Old August 30th 07, 04:50 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
AustinMN
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Posts: 234
Default 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

  #8  
Old August 30th 07, 04:55 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
gwatts
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Posts: 9
Default 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/
  #9  
Old August 30th 07, 05:03 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
George Dishman[_1_]
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Posts: 2,509
Default 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


  #10  
Old August 30th 07, 05:22 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
laura halliday
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Posts: 168
Default 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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