What is the highest radio frequency used for radio astronomy?

In sci.astro.amateur gwatts wrote:
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.

Hi, Peter, and thank you for your correct conclusion that in my post
I really wasn't concerned with transparency or propagation questions,
only with the general question of how to describe what I now have learned
is often called the submillieter portion of the spectrum.


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.

That sounds to me like good summary, which would also fit what I recall
from the 1960's about certain regions of EHF -- maybe around 60GHz or
so -- where attentuation or extinction from water vapor is especially
notable. Maybe this is a bit analogous to the absorption lines of
visual spectroscopy.

Of course, as Laura has pointed out, in space this kind of attenuation
is not really a problem!

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/

Thanks for these links, which I'll study.

Most appreciatively,

Margo Schulter

Lat. 38.566 Long. -121.430

Bob Downonit wrote:

On 2007-09-02 11:37:04 -0400, BradGuth said:

On Aug 31, 6:44 am, Chris L Peterson wrote:
On Fri, 31 Aug 2007 12:13:05 GMT, (Paul Schlyter) wrote:
That's a little illogical. It's like considering a frequency slightly
above 300 kHz to belong to "the Megahertz band" ....

No, it's _more_ logical. It's having arbitrary names for various regions
of the EM spectrum that isn't entirely logical.

_________________________________________________

Chris L Peterson
Cloudbait Observatoryhttp://www.cloudbait.com

Most all ET signals are processed by some kind of technology, so that
we can then see or hear the information contained within that signal.
If the signal information is encrypted or otherwise weird, then seeing
the signal is usually the better alternative.

I believe 0.1 TeraHertz of 3 mm is more than good enough, as being
roughly 10 fold higher in frequency than any X Band radar imaging
efforts sent from Earth would ever manage to contribute all that much
due to our terrestrial atmosphere and magnetosphere that'll convert
and/or divert much of that outgoing and incoming X Band energy.

However, a blue/violet laser cannon would likely become by far the
most energy efficient and focused alternative for outgoing as well as
incoming signals, especially if those efforts were getting off-world
managed, such as within the nearby turf of our moon's L1 could easily
accommodate. At least in that way an amateur terrestrial or ET
astronomer could rather easily detect such without special
instruments.

There's all kinds of nifty ways for us to hear and/or see what our
moon has to say. It's sodium populated atmosphere along with the
surface likes of radon are worth a good deal of science about solar
wind and cosmic interactions, as well as for the graviton/tidal issues
associated with having to orbit Earth as well as the sun that should
be responsible for keeping the low density core of our moon a little
extra toasty, as a renewable geothermal cache of energy that could
essentially accommodate a fairly extensive underground protected human
use of our moon.
- Brad Guth


You're a ****tard.

IAWTP.

http://www.caballista.org/auk/kookle.php?search=guth

--
Official Overseer of Kooks and Saucerheads for alt.astronomy
Wee Davie Tholen is a grade-school lamer
Trainer and leash holder of:
Honest "Clockbrain" John
nightbat "fro0tbat" of alt.astronomy
Tom "TommY Crackpotter" Potter
http://www.caballista.org/auk/kookle.php?search=deco

"You really are one of the litsiest people I know, Mr. Deco."
--Kali, quoted endlessly by David Tholen as evidence of "something"

"Why are you now discussing Art Deco, rec.music.classical,
the coward using a fake name who avoids answering questions
and doesn't try to discuss music with anyone?"
--David Tholen

"Quite a kook-out, Deco. You've been frothing even more
ever since I demonstrated how you believe that ah's family
name is "ah"."
--David Tholen

In article .com,
Radium wrote:

On Sep 2, 2:42 am, (Paul Schlyter) wrote:
................
Another interesting experience is to feed a digital signal directly to
a loudspeaker instead of decoding and converting it to an analog
signal first. That of course requires that the digital signal is
within the audible range of frequencies -- the signal from a
traditional telephone modem would be quite suitable here. The old 300
bps modems produced a signal with a quite clear structure (the signal
jumped between two frequencies 300 times per second), but the more
modern telephone modems which can handle bit rates up to 57600 bps,
they sound pretty much like white noise to the human ear.

Interesting indeed. However, are those old modems really "digital"?

On one side only ..... the signal sent out on the phone line is of
course analog. So what one listens at is a digital signal modulating
one or several analog carriers. And this applies not only to old
modems but to new modems as well. E.g. ADSL modems work pretty much
the same way, except that an ADSL modem has severam MHz of analogue
bandwidth available, compared to the 3 kHz of bandwidth an old
telephone modem has available.


That's why audio software is often used to speed up the infrasound
until it is at least 20 Hz so that humans can hear it.

:-) ....there's no need to speed it up just to convert the frequency
into the audible range.... the frequency can be bumped up even if
the original speed is maintained.

Is this done using audio software such as Adobe Audition?

Quotes from http://www.adobe.com/products/audition/overview2.html :

"Time and pitch processing: Change tempo without shifting pitch - or
shift pitch without changing tempo - and never introduce audio
artifacts."

Obviously one can use Audio Audition for that. It could even be done
several decades ago, using analogue techniques.

Another possible way would be to let the low frequency signal
amplitude modulate a carrier with an audible freqneucy, and then
filter away the carrier as well as the lower side band. This will
have the effect of adding a fixed frequency (the carrier frequency) to
all frequencies in the low frequency signal. Ham radio operators
using SSB will know exactly what I'm talking about.

using an AM receiver as opposed to an FM receiver. FM is immune to the
disruptions that normally affect AM.

Did you ever try to tune an FM receiver between radio stations on the
FM band? Also turn off any "muting" or "squelch" the receiver may have.
What do you hear? Silence? Or perhaps noise?

White noise. Hissing. Nothing special.

Most signals received by radio telescopes will "sound" pretty much
the same.

Btw, did you know that you can use an FM radio to observe meteor
showers? CHoose a radio station which normally is a little bit too
far away to hear, then direct your antenna towards it. Next, wait for
the meteors - and listen to your radio station briefly as its radio
waves are reflected against the meteor trail....



--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

On Sep 2, 11:42 pm, (Paul Schlyter) wrote:

In article .com,

Radium wrote:

Is this done using audio software such as Adobe Audition?

Quotes fromhttp://www.adobe.com/products/audition/overview2.html:

"Time and pitch processing: Change tempo without shifting pitch - or
shift pitch without changing tempo - and never introduce audio
artifacts."

Obviously one can use Audio Audition for that. It could even be done
several decades ago, using analogue techniques.

What analogue methods were used for this pitch-shifting? Were they as
efficient as audio softwares?

White noise. Hissing. Nothing special.

Most signals received by radio telescopes will "sound" pretty much
the same.

Okay.

Btw, did you know that you can use an FM radio to observe meteor
showers?

I didn't know that.

CHoose a radio station which normally is a little bit too
far away to hear, then direct your antenna towards it. Next, wait for
the meteors - and listen to your radio station briefly as its radio
waves are reflected against the meteor trail....

Does the meteor shower make a buzzing sound on FM radio stations?

On Sep 1, 5:16 am, Radium wrote:
On Aug 30, 4:33 am, gwatts wrote:

Radium wrote:

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?

I suppose it depends what exactly you mean by "radio astronomy". Radio
astronomers have been extending the original radio techique of Earth
Rotation Aperture Sythesis up into the IR and near optical bands
recently. As such the highest frequency at which a fringe baseline
correlator has been operated for astronomy is now in the visible band.
COAST and the NRAO optical interferometer group have both produced
indirect images of the sky using radio correlator methods implemented
by very cunning mechanical optical bench designs at visible
wavelengths.

If you read on a little farther you'll find
'blurring the distinction between radio astronomy and infrared astronomy.'

Many of the early microwave groups spun out of radio astronomy
sections. The catch is that at least for a while the non-thermal
sources get significantly fainter with increasing frequency (fewer
higher energy photons get emitted).

So where do you want to draw the line between radio astronomy and
infrared astronomy? There's you're answer.

Sorry, I meant to ask whether 3,438 GHz is the highest radio frequency
used to receive audio signals from outer space. I should have made my
question more specific. Radio-astronomers study sounds from the sun as
well as visual data.

Although they do study movements of the suns surface by Doppler shift
of known reference spectral wavelengths this is something entirely
different to what radio astronomers do. Very few big radio telescopes
enjoy being pointed at the sun.

I wonder if a space station with a 3,438 GHz AM receiver could pick up
any extremely-distant audio signals between 20 to 20,000 Hz [from
magnetars, gamma-ray-bursts, supernovae and other high-energy but
cosmic objects] after demodulating the 3,438 GHz AM carrier wave.- Hide quoted text -

There is no carrier wave (unless you happen to chose a specific
naturally occurring spectral wavelength like 21cm neutral hydrogen for
instance). The telescope operator choses the frequency and bandwidth
they receive - the source is normally a broadband emitter.

Most objects emit broadband thermal radiation determined by their
characteristic temperature and broadband non-thermal radiation
determined by a combination of shockwaves, magnetic fields and fast
particle interactions. It would sound like the white noise on a
detuned radio reciever if you were to put it on a speaker. Pulsars are
the only obvious exception where there is clear periodic structure in
the signal.

Jupiter sometimes provided faintly interesting amplitude modulation of
its radio emission that should be within the reach of a decent amateur
short wave receiver with a directional antenna to listen into.

Regards,
Martin Brown

On Sep 3, 1:08 am, Martin Brown
wrote:

On Sep 1, 5:16 am, Radium wrote:

On Aug 30, 4:33 am, gwatts wrote:

Radium wrote:

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?

I suppose it depends what exactly you mean by "radio astronomy". Radio
astronomers have been extending the original radio techique of Earth
Rotation Aperture Sythesis up into the IR and near optical bands
recently. As such the highest frequency at which a fringe baseline
correlator has been operated for astronomy is now in the visible band.
COAST and the NRAO optical interferometer group have both produced
indirect images of the sky using radio correlator methods implemented
by very cunning mechanical optical bench designs at visible
wavelengths.

A radio-wave can travel a larger distance with less attenuation than
an infrared or light wave. Objects in the path that allow radio-waves
to pass undisturbed can have a serious impact on optical
telecommunications.

If you read on a little farther you'll find
'blurring the distinction between radio astronomy and infrared astronomy.'

Many of the early microwave groups spun out of radio astronomy
sections. The catch is that at least for a while the non-thermal
sources get significantly fainter with increasing frequency (fewer
higher energy photons get emitted).

Microwaves have characteristics that more closely resembles radio-
waves than light/infrared waves.

So where do you want to draw the line between radio astronomy and
infrared astronomy? There's you're answer.

Sorry, I meant to ask whether 3,438 GHz is the highest radio frequency
used to receive audio signals from outer space. I should have made my
question more specific. Radio-astronomers study sounds from the sun as
well as visual data.

Although they do study movements of the suns surface by Doppler shift
of known reference spectral wavelengths this is something entirely
different to what radio astronomers do. Very few big radio telescopes
enjoy being pointed at the sun.

What happens to a radio telescope when directed toward the sun?

I wonder if a space station with a 3,438 GHz AM receiver could pick up
any extremely-distant audio signals between 20 to 20,000 Hz [from
magnetars, gamma-ray-bursts, supernovae and other high-energy but
cosmic objects] after demodulating the 3,438 GHz AM carrier wave

There is no carrier wave (unless you happen to chose a specific
naturally occurring spectral wavelength like 21cm neutral hydrogen for
instance). The telescope operator choses the frequency and bandwidth
they receive - the source is normally a broadband emitter.

I would guess the higher the frequency of the radio-wave reception,
the better it is for this application. This is because higher-
frequency radio waves can more easily pass through ionospheric
elements [such as the heliosphere around our solar system] than lower-
frequency radio waves.

The above assumes the reception occurs in space itself [e.g. on a
space station]. On Earth, the higher end of the radio spectrum tends
to be opaque to the atmosphere while the lower end is blocked by the
ionosphere. Hence, if the experiment is done on Earth, you can't go
too high or too low [even within the "radio spectrum"]. The limits are
stricter on Earth than in outer-space. In space, you don't have these
limits as long as you stay in the radio band.

Most objects emit broadband thermal radiation determined by their
characteristic temperature and broadband non-thermal radiation
determined by a combination of shockwaves, magnetic fields and fast
particle interactions. It would sound like the white noise on a
detuned radio reciever if you were to put it on a speaker. Pulsars are
the only obvious exception where there is clear periodic structure in
the signal.

What would the pulsars sound like in this experiment? Square-waves?

Jupiter sometimes provided faintly interesting amplitude modulation of
its radio emission that should be within the reach of a decent amateur
short wave receiver with a directional antenna to listen into.

I've been to certain websites containing recordings of these
emissions. They sound like strong winds.

On Sep 3, 9:14 pm, Radium wrote:
On Sep 3, 1:08 am, Martin Brown
wrote:

On Sep 1, 5:16 am, Radium wrote:
On Aug 30, 4:33 am, gwatts wrote:
Radium wrote:
What is thehighestradiofrequency used forradioastronomy?

I suppose it depends what exactly you mean by "radioastronomy".Radio
astronomers have been extending the originalradiotechique of Earth
Rotation Aperture Sythesis up into the IR and near optical bands
recently. As such thehighestfrequency at which a fringe baseline
correlator has been operated forastronomyis now in the visible band.
COAST and the NRAO optical interferometer group have both produced
indirect images of the sky usingradiocorrelator methods implemented
by very cunning mechanical optical bench designs at visible
wavelengths.

Aradio-wave can travel a larger distance with less attenuation than
an infrared or light wave. Objects in the path that allowradio-waves
to pass undisturbed can have a serious impact on optical
telecommunications.

Make your mind up. You asked about the highest frequency used by radio
astronomers.

If you read on a little farther you'll find
'blurring the distinction betweenradioastronomyand infraredastronomy.'
Many of the early microwave groups spun out ofradioastronomy
sections. The catch is that at least for a while the non-thermal
sources get significantly fainter with increasing frequency (fewer
higher energy photons get emitted).

Microwaves have characteristics that more closely resemblesradio-
waves than light/infrared waves.

They are all electromagnetic radiation. The transparency or otherwise
varies somewhat with wavelength.

So where do you want to draw the line betweenradioastronomyand
infraredastronomy? There's you're answer.
Sorry, I meant to ask whether 3,438 GHz is thehighestradiofrequency
used to receive audio signals from outer space. I should have made my
question more specific.Radio-astronomers study sounds from the sun as
well as visual data.
Although they do study movements of the suns surface by Doppler shift
of known reference spectral wavelengths this is something entirely
different to whatradioastronomers do. Very few bigradiotelescopes
enjoy being pointed at the sun.

What happens to aradiotelescope when directed toward the sun?

The receiving electronics get warmed up by the partially focussed
image of the sun. Or in the case of a catadiotric design the secondary
reflector gets warmed up and potentially distorted by thermal
expansion.

Scopes intended to be pointed at the sun are designed with that
purpose in mind.

There is no carrier wave (unless you happen to chose a specific
naturally occurring spectral wavelength like 21cm neutral hydrogen for
instance). The telescope operator choses the frequency and bandwidth
they receive - the source is normally a broadband emitter.

I would guess the higher the frequency of theradio-wave reception,
the better it is for this application. This is because higher-

Not really radio astronomy is now operating between around 35MHz and
upwards. There are difficulties with gettign coherent signals, but
once 3 or more scopes are linked together there are good observables.

The biggest problem for radio astronomy is that radio objects mostly
get dimmer with increasing frequency. And there are some bands like
the terahertz where there are very few natural processes capable of
emitting them.

Most objects emit broadband thermal radiation determined by their
characteristic temperature and broadband non-thermal radiation
determined by a combination of shockwaves, magnetic fields and fast
particle interactions. It would sound like the white noise on a
detunedradioreciever if you were to put it on a speaker. Pulsars are
the only obvious exception where there is clear periodic structure in
the signal.

What would the pulsars sound like in this experiment? Square-waves?

No. They are sharp narrow pulses roughly 1:100 to 1:1000 mark space
ratio with a broad spectrum of harmonics (a square wave would be 1:1).
You can listen to some pulsar waveforms online at Jodrell Bank:

http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html

Regards,
Martin Brown

In article . com,
Martin Brown wrote:

Microwaves have characteristics that more closely resemblesradio-
waves than light/infrared waves.

They are all electromagnetic radiation. The transparency or otherwise
varies somewhat with wavelength.

What distinguishes them are really our technology:

Radio waves have wavelengths which are much larger than the components
we use to receive them.

Microwaves have wavelengths which are comparable in size to the
components we use to receive them. In practice, this wavelength band
has shifted towards shorter wavelengths as the miniaturization of our
electronics has progressed - wavelengths which earlier (50+ years ago)
had to be amplified using specially designed microwave valves can
nowadays be amplified with more conventional (and much smaller)
electronic components.

Optical (IR/light/UV) waves have wavelengths which are much shorter
than the components we use to receive them.

Finally, we have X-rays and gamma rays, where normal optics no longer
can be used since it's hard or impossible to construct optical
elements which refract or reflect them. There we often use photon
counters instead. Special optics can sometimes be used for some of
these wavelength bands though, such as Wolter telescopes for X-rays
which use grazing incidence to its optical surfaces to be able to
reflect X-rays.



A common satellite receiver's dish is a mixture of the three first
kinds of components: the parabolic reflector is a typical optical
component, the LNB uses microwave techniques to convert the 10-12 GHz
frequency to something between 1 and 2 GHz instead, and the satellite
receiver uses conventional electronics.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

On Sep 3, 12:11 am, Radium wrote:
On Sep 2, 11:42 pm, (Paul Schlyter) wrote:

Btw, did you know that you can use an FM radio to observe meteor
showers?

I didn't know that.

CHoose a radio station which normally is a little bit too
far away to hear, then direct your antenna towards it. Next, wait for
the meteors - and listen to your radio station briefly as its radio
waves are reflected against the meteor trail....

Does the meteor shower make a buzzing sound on FM radio stations?

No. You hear brief bursts of the station, reflected off the
ionization trail.

This happens with television too. VHF signals can reflect
off other things too, like auroras and patches of intense
ionization in the E layer ("E Layer Skip"). Sporadic E
signals can be extremely strong.

Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer

Martin Brown wrote:

What would the pulsars sound like in this experiment? Square-waves?

No. They are sharp narrow pulses roughly 1:100 to 1:1000 mark space
ratio with a broad spectrum of harmonics (a square wave would be 1:1).
You can listen to some pulsar waveforms online at Jodrell Bank:

http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html

Regards,
Martin Brown

Impressive sounds!! Thanks.