What is the highest radio frequency used for radio astronomy?

On Aug 30, 4:33 am, 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.

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.

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.

In article .com,
Radium wrote:

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.

Radio astronomers study EM radiation, not "sounds", from the Sun.
Since there's a vacuum between the Sun and us, no sound waves would be
able to propagate from the Sun to us. Otoh careeful studies of
Doppler shifts have enabled solar astronomers to study sound waves
*within* the Sun. But these sound waves never reach us - we can only
study them indirectly because they move matter near the solar surface.
And their frequencies are usually well below what the human ear can
hear, i.e. it's infrasound.

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.

They could certainly try .... but if they did, and succeeded, it would
sound just like noise. This radiation does not originate as audio
signals, and they're certainly not put on an AM modulated carrier.
Therefore it's hardly useful to try to demodulate these waves as if
they were AM modulated signals - there's e.g. no AM carrier (i.e. one
single frequency which is stronger than all the others within the
frequency band).

Also, any audio (= pressure waves within a gas) which are formed
outside the Earth is certainly *not* limited to the 20 to 20,000
Hz frequency range..... that frequency range is merely the limits
of what the human ear can hear.

--
----------------------------------------------------------------
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 1, 1:12 am, (Paul Schlyter) wrote:

In article .com,

Radium wrote:
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.

Radio astronomers study EM radiation, not "sounds", from the Sun.
Since there's a vacuum between the Sun and us, no sound waves would be
able to propagate from the Sun to us.

The radio-frequency EM radiation emitted from the sun does translate
to sound when it is picked up by a radio receiver of the same carrier
frequency.

Otoh careeful studies of
Doppler shifts have enabled solar astronomers to study sound waves
*within* the Sun. But these sound waves never reach us - we can only
study them indirectly because they move matter near the solar surface.
And their frequencies are usually well below what the human ear can
hear, i.e. it's infrasound.

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.

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.

They could certainly try .... but if they did, and succeeded, it would
sound just like noise. This radiation does not originate as audio
signals, and they're certainly not put on an AM modulated carrier.

Well, most natural sources of EMI and RFI are amplitude-modulated. The
audio signals are not put on the carrier wave, however if the
variations in the peak-to-peak amplitude of the 3,438 GHz
electromagnetic waves correspond to frequencies between 20 and 20,000
Hz [and the peak-to-peak variations are sufficient in power], then the
signal can be picked up of 3,438 GHz receiver and demodulated. The
result would be audio signals.

Therefore it's hardly useful to try to demodulate these waves as if
they were AM modulated signals - there's e.g. no AM carrier (i.e. one
single frequency which is stronger than all the others within the
frequency band).



Also, any audio (= pressure waves within a gas) which are formed
outside the Earth is certainly *not* limited to the 20 to 20,000
Hz frequency range..... that frequency range is merely the limits
of what the human ear can hear.

Audio waves from 20 to 20,000 Hz can be derived from demodulating
radio waves. Since most natural radio disruptions are amplitude-
modulated it would be easier to listen to cosmic sounds using an AM
receiver as opposed to an FM receiver. FM is immune to the disruptions
that normally affect AM.

In AM demodulation:

1. The amplitude of the demodulated signal [what we hear] is
determined by the depth-of-change of the peak-to-peak amplitude of the
radio wave. If the peak-to-peak amplitude of the radio wave is above
the central amplitude** then the demodulated signal will have a
positive voltage. If the peak-to-peak amplitude of the radio wave is
below the central amplitude then the demodulated signal will have a
negative voltage. If these changes in voltages are between 20 and
20,000 Hz*, then they will be audible if the over voltage is high-
enough and this signal is fed into a loudspeaker
2. The frequency of the demodulated signal is determined by the rate-
of-change of the peak-to-peak amplitude of the radio wave

*In an electric signal, a cycle is when a voltage changes from zero to
positive to zero to negative and then back to zero. In USA, the power
supply is 60 Hz [cycles per second] while being 50 Hz in Europe. In
order to produce audible sound when fed to a loudspeaker, the peak-to-
peak voltage must be high-enough to reach the threshold of hearing or
above and must be at least 20 Hz but no more than 20,000 Hz.

A loudspeaker produces the mechanical equivalent of the electric
signal it receives.

** Central amplitude = amplitude of the radio wave when there is no
modulation signal.

In article .com,
Radium wrote:

On Sep 1, 1:12 am, (Paul Schlyter) wrote:

In article .com,

Radium wrote:
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.

Radio astronomers study EM radiation, not "sounds", from the Sun.
Since there's a vacuum between the Sun and us, no sound waves would be
able to propagate from the Sun to us.

The radio-frequency EM radiation emitted from the sun does translate
to sound when it is picked up by a radio receiver of the same carrier
frequency.

Here you make the silent assumption that the electric signal from the
radio receiver is fed to a loudspekarer. But that's just *one*
possible way of converting the EM radiation. You could use other ways
too. For instance displaying it on some video screen - those who do
so could claim that "The radio-frequency EM radiation emitted from the
sun does translate to light when it is picked up by a radio receiver
of the same carrier frequency" (with the silent assupmtion that the
output from the receiver is displayed on a video screen). It's the
translator who decides what the EM radiation translates to....

Btw did you ever try to *listen* to a TV transmission? I mean, to feed
the *video* signal (not the audio signal) to a loudspeaker instead
of a video screen? Yep, the sound changes with the contents of the
picture - but of course one hears only the lowermost part of the 5 MHz
of bandwidth a normal video signal has.

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.

Otoh careeful studies of
Doppler shifts have enabled solar astronomers to study sound waves
*within* the Sun. But these sound waves never reach us - we can only
study them indirectly because they move matter near the solar surface.
And their frequencies are usually well below what the human ear can
hear, i.e. it's infrasound.

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.

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.

They could certainly try .... but if they did, and succeeded, it would
sound just like noise. This radiation does not originate as audio
signals, and they're certainly not put on an AM modulated carrier.

Well, most natural sources of EMI and RFI are amplitude-modulated.

They're probably frequency modulated and phase modulated as well,
since their contents are pretty random. I strongly doubt they consist
of one single frequency whose amplitude varies while its frequency and
phase remains unchanged (that's the way a properly modulated AM signal
would be). In particular it won't have symmetrical sidebands with the
same content, the way a real AM signal should have.

The audio signals are not put on the carrier wave, however if the
variations in the peak-to-peak amplitude of the 3,438 GHz
electromagnetic waves correspond to frequencies between 20 and 20,000
Hz [and the peak-to-peak variations are sufficient in power], then the
signal can be picked up of 3,438 GHz receiver and demodulated. The
result would be audio signals.

Trivially true -- but these audio signals would be created by us
humans. They're not inherent in the original signal.

Therefore it's hardly useful to try to demodulate these waves as if
they were AM modulated signals - there's e.g. no AM carrier (i.e. one
single frequency which is stronger than all the others within the
frequency band).

Also, any audio (= pressure waves within a gas) which are formed
outside the Earth is certainly *not* limited to the 20 to 20,000
Hz frequency range..... that frequency range is merely the limits
of what the human ear can hear.

Audio waves from 20 to 20,000 Hz can be derived from demodulating
radio waves.

You can create audio waves also below 20 Hz and above 20,000 Hz as
well. Humans won't hear them, true, but dogs and bats might enjoy them... :-)

Since most natural radio disruptions are amplitude-
modulated it would be easier to listen to cosmic sounds

These sounds aren't "cosmic" - they're created here on Earth by us humans.

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?

You say "FM is immune to the disruptions that normally affect AM". If
this is to work, you must have an FM carrier which is strong enough
for the receivers amplitude limitation circuits to work well. Cosmic
radio noise is far too weak for that.


description of AM and definition of frequency snipped
--
----------------------------------------------------------------
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 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

On Aug 30, 12:33 am, 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?

Thanks,

Radium
For obtaining eye candy that's entirely outside of our physical reach,
and for the most part having been getting further away as we speak,
the 3.438 THz might be fine and dandy for accomplishing that spendy
look-see which can't possibly benefit humanity or that of our badly
failing environment.

Much above 0.1 THz is where such photons if transmitted from Earth
simply do not reflect unless the target offers a nifty array of
parabolic dishes, or of some other artificial reflective surface.
Outside of our magnetosphere, such as within our moon's L1, is where X
band of 8 ~ 12.5 GHz or possibly as great as Ka Band of 26.5 ~ 40 GHz
might become interesting and/or essential if future space travel is to
avoid those nasty bits and pieces of debris that'll otherwise clean
your clock upon encountering such, with C Band of 4 ~ 8 GHz being a
little better off for those slightly larger targets and perhaps best
of all S Band of 2 ~ 4 GHz offering a compromise that'll still yield
more than sufficient image resolution of a given planet or moon, along
with offering a darn good reflective signal to noise ratio.

However, if the potential target is the least bit intelligent worthy,
as many should be, as such why not use a blue~violet laser cannon, UV-
a, or possibly good old X-rays or even gamma ?

Though gravity can be directly measured, of what we can't manage thus
far is the two-way frequency applications of utilizing said
gravitons. Perhaps there again, the mutual gravity nullification zone
of our moon's L1 could allow for the limited use of gravitons, and
this alternative might become better yet once we've relocated that
moon to Earth's L1.
- Brad Guth