What is the highest radio frequency used for radio astronomy?
Radium
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?record_id=11719&page=11
Is 3438 GHz the highest radio frequency used for radio astronomy?
Thanks,
Radium
gwatts
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.
zanthi...@gmail.com
> infrared astronomy? There's you're answer.
Why don't you just call it all electromagnetic astronomy?
gwatts
It's not my call.
Margo Schulter
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
msch...@calweb.com
Lat. 38.566 Long. -121.430
Peter Webb
"Margo Schulter" <msch...@web1.calweb.com> wrote in message
news:46d6dc3b$0$34291$d36...@news.calweb.com...
So its your contention that the atmosphere is transparent all the way up
from microwaves to IR?
AustinMN
<webbfam...@DIESPAMDIEoptusnet.com.au> wrote:
> "Margo Schulter" <mschul...@web1.calweb.com> wrote in message
> > 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
gwatts
>
...
>
> 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-memos/alma187/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/presentations/ALMA_2007_Handout.pdf
and of course the entire ALMA/MMA Memo Series,
http://www.alma.info/
George Dishman
"Peter Webb" <webbf...@DIESPAMDIEoptusnet.com.au> wrote in message
news:46d6e391$0$6690$afc3...@news.optusnet.com.au...
> "Margo Schulter" <msch...@web1.calweb.com> wrote in message
> news:46d6dc3b$0$34291$d36...@news.calweb.com...
>> In sci.astro.amateur gwatts <gwa...@frontiernet.net> 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?record_id=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/what_is_submillimeter.htm
George
laura halliday
> 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
Chris L Peterson
wrote:
>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).
They are called submillimeter waves, and represent the transition
between what is widely accepted as "radio" and what is widely accepted
as "optical".
IMO the best way to categorize EM bands is by the nature of the
equipment we use to measure energy in those bands. Submillimeter
radiation is detected using special receivers which combine optical-like
sensors (bolometers) and radio-like sensors (heterodyne receivers and
tuned antennas). I think its best to simply consider the range from
about one millimeter to 1/10 millimeter as "submillimeter", neither
radio nor optical (IR).
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
Profumo
She didnt say anything at all about this. Why are you "contending"
contenacity contumaciously?
Paul Schlyter
Chris L Peterson <c...@alumni.caltech.edu> wrote:
> IMO the best way to categorize EM bands is by the nature of the
> equipment we use to measure energy in those bands. Submillimeter
> radiation is detected using special receivers which combine optical-like
> sensors (bolometers) and radio-like sensors (heterodyne receivers and
> tuned antennas). I think its best to simply consider the range from
> about one millimeter to 1/10 millimeter as "submillimeter", neither
> radio nor optical (IR).
Or perhaps we could consider that wavelength band both "optical" and
"radio", since radiation at those wavelengths probably can be detected
both with radio and with optical equipment.
And if one wants to decide on some single wavelength limit between
"radio" and "optical", 0.3 millimeter appears to be a good choice
since it resides near the middle of this "submillimeter" band. This
corresponds to a frequency of one TeraHertz.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
Paul Schlyter
laura halliday <mars...@hotmail.com> wrote:
> 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.
Given today's CCD chips which indeed are electronic devices, does that
mean todays optical telescopes, with CCD chips which detect light
electronically, have become radio telescopes?
Dan Tilque
>
> And if one wants to decide on some single wavelength limit
> between "radio" and "optical", 0.3 millimeter appears to be a
> good choice since it resides near the middle of this
> "submillimeter" band. This corresponds to a frequency of one
> TeraHertz.
And in fact, e-m radiation at and around that frequency is often
called Terahertz radiation, or Terahertz waves, or T-rays, etc.
More specifically, from 300 GHz to 3 THz is the Terahertz band.
This terminology seems to be used more in non-astronomical
fields.
http://en.wikipedia.org/wiki/Terahertz
--
Dan Tilque
Paul Schlyter
That's a little illogical. It's like considering a frequency slightly
above 300 kHz to belong to "the Megahertz band" ....
>--
>Dan Tilque
Richard Tobin
Paul Schlyter <pau...@saaf.se> wrote:
>That's a little illogical. It's like considering a frequency slightly
>above 300 kHz to belong to "the Megahertz band" ....
Seems logical to me. Anything above 316kHz is nearer to 1MHz than to
100kHz.
-- Richard
--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.
Paul Schlyter
Richard Tobin <ric...@cogsci.ed.ac.uk> wrote:
>In article <fb8v7n$13it$1...@merope.saaf.se>,
>Paul Schlyter <pau...@saaf.se> wrote:
>
>>That's a little illogical. It's like considering a frequency slightly
>>above 300 kHz to belong to "the Megahertz band" ....
>
>Seems logical to me. Anything above 316kHz is nearer to 1MHz than to
>100kHz.
There's a difference between "the Megahertz band" and "the One Megahertz
band". The former can be interpreted as the band from 1 MHz to 1 GHz
for instance, instead of your interpretation from 0.316 to 3.16 MHz....
>-- Richard
>
>--
>"Consideration shall be given to the need for as many as 32 characters
>in some alphabets" - X3.4, 1963.
Chris L Peterson
>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.
BradGuth
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
laura halliday
> In article <1188490924.299814.37...@e9g2000prf.googlegroups.com>,
> laura halliday <marsga...@hotmail.com> wrote:
>
> > 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.
>
> Given today's CCD chips which indeed are electronic devices, does that
> mean todays optical telescopes, with CCD chips which detect light
> electronically, have become radio telescopes?
Can't say I agree with that; CCDs count photons, which makes
them a lot closer to bolometers than diodes.
The other issue, of course, is just what difference it makes.
Astronomers examine the universe to see how it works.
They use various wavelengths to do it.
Chris L Peterson
and it is unlikely that neighbors suspected anything out of the ordinary.
But the inside was anything but ordinary. There were scores of rooms crammed
with administrative functions, equipment, wires, jury-rigged gizmos, a
currency bank, and computers.
Every electronic intercept capability NSA denied having was right there.
In a small black box, not much bigger than a briefcase, was "Oratory."
This portable key-word selection computer could be taken almost anywhere
and set to pick out pre-selected words and automatically monitor and
record fax, voice, or teletype messages that contained them.
Developed by NSA, "Oratory" was "tempest-proof" (i.e. shielded to
prevent emmisions that could lead to detection), small, virtually
indestructible, and easy to repair: all you had to do was open the
lid and replace the self-diagnosed defective component.
[snip]
In pursuit of plausible deniability, CSE, GCHQ, and NSA have used each
others' personnel and resources to evade laws against domestic spying.
[ an example given in whi
Radium
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.
Paul Schlyter
Radium <gluc...@gmail.com> 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.
Radium
> In article <1188620214.390706.118...@r29g2000hsg.googlegroups.com>,
> Radium <gluceg...@gmail.com> 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.
Paul Schlyter
Radium <gluc...@gmail.com> wrote:
> On Sep 1, 1:12 am, pau...@saaf.se (Paul Schlyter) wrote:
>
>> In article <1188620214.390706.118...@r29g2000hsg.googlegroups.com>,
>
>> Radium <gluceg...@gmail.com> 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>
BradGuth
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
Radium
> In article <1188683416.066878.250...@d55g2000hsg.googlegroups.com>,
> Radium <gluceg...@gmail.com> wrote:
> > 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.
I've done this before. Plugged the video signal into the audio
receiver. There is some buzzing sound. As you said, that sound changes
as video signal changes.
> 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"?
> > 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."
> > 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.
Art Deco
>I believe
No one cares, Brad.
--
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
Margo Schulter
>
> 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.
Hi, Laura, and thanks to you and others very helpful responses
on this point. A bit of browsing the Web has shown me that
definitions can vary, for example with the portion of the
submillimeter spectrum around 300 GHz - 1 THz (or 1mm - 300um)
being considered as more "radio-like" by some.
> 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?
Exactly; and it's interesting some of the special environments
which are above most of the atmosphere's water vapor, or
dessicated, that are used for terrestrial observations at
certain points in the EHF and submilliter spectrum.
Margo Schulter
>>
> ...
>>
>> 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-memos/alma187/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/presentations/ALMA_2007_Handout.pdf
>
> and of course the entire ALMA/MMA Memo Series,
> http://www.alma.info/
Thanks for these links, which I'll study.
Bob Downonit
You're a fucktard.
Art Deco
Paul Schlyter
Radium <gluc...@gmail.com> wrote:
> On Sep 2, 2:42 am, pau...@saaf.se (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....
Radium
> In article <1188764496.354935.257...@r29g2000hsg.googlegroups.com>,
> Radium <gluceg...@gmail.com> 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?
Martin Brown
> On Aug 30, 4:33 am, gwatts <gwa...@frontiernet.net> 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?record_id=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
Radium
wrote:
> On Sep 1, 5:16 am, Radium <gluceg...@gmail.com> wrote:
> > On Aug 30, 4:33 am, gwatts <gwa...@frontiernet.net> 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?record_id=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.
Bob Downonit
> IAWTP.
>
> <http://www.caballista.org/auk/kookle.php?search=guth>
LOL!
Martin Brown
> On Sep 3, 1:08 am, Martin Brown <|||newspam...@nezumi.demon.co.uk>
> wrote:
>
> > On Sep 1, 5:16 am, Radium <gluceg...@gmail.com> wrote:
> > > On Aug 30, 4:33 am, gwatts <gwa...@frontiernet.net> 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/Education/Sounds/sounds.html
Regards,
Martin Brown
Paul Schlyter
Martin Brown <|||newspam|||@nezumi.demon.co.uk> 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.
laura halliday
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.
Sjouke Burry
>> 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/Education/Sounds/sounds.html
>
> Regards,
> Martin Brown
>
Impressive sounds!! Thanks.
Paul Schlyter
laura halliday <mars...@hotmail.com> wrote:
> 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.
...except that VHF television is vanishing. In Sweden, the very last
VHF TV transmitters will close down this fall - most of them already
have closed down. After that, we only have digital UHF television.
Other European countries are expected to do the same within a few
years.
And UHF signals don't reflect as well off sporadic E layes.
Per Erik Jorde
> ...except that VHF television is vanishing. In Sweden, the very last
> VHF TV transmitters will close down this fall - most of them already
> have closed down. After that, we only have digital UHF television.
> Other European countries are expected to do the same within a few
> years.
More problematically: digital transmissions (TV or radio) have delays in
them that makes the time signal unreliable. Where to get reliable
time signals for time-critical observations (astrometry, occultation
timings, etc.) from now on?
pej
--
Per Erik Jorde
Paul Schlyter
That was a change of subject, but OK.....
We still have shortwave radio time signals. Here in Europe, Moscow
transmits more or less continuously at 4996, 9996 and 14996 kHz - at
least one of these frequencies can be heard any time of the day or
night. This requires a shortwave receiver capable of reveicing CW
or SSB though.
And then you can get a radio controlled clock, which here in Europe
is controlled by the transmitter in Mainflingeln, Germany, which
transmits at (I believe) 77.5 kHz, i.e. in the LF band. I've
checked a few radio controlled clocks against time signals, and
they agree "exactly" as far as my eye and ear could determine
(which means any discrepancy is less than approx. 0.1 seconds).
Finally, if you want to be really "hi-tech", there are always the
GPS satellites, which transmit time information to a very high
accuracy. The typical GPS receiver units are pretty bad at displaying
this time info at the right time though - there's a typical delay of
some 1 to 2 seconds in the displayed time. There are probably other
GPS receivers which makes the GPS time available to a much higher
accuracy, but these units probably cost much more. The CW/SSB
shortwave radio receiver or the radio conrolle clock will be much
cheaper.
Personally I've never used TV transmissions as a time source with
high accuracy - I've always used radio controlled clocks, or shortwave
time signals.
People in North America can use shortwave time signals from WWV
in the US, or CHU in Canada. These transmitters use AM, not CW, for
their transmissions. The advantage for the user is that any shortwave
receiver can be used for these transmissions -- CW/SSB capability of
the receiver os not needed. The disadvantage for the user is that
AM transmissions don't reach quite as far as CW transmissions - if
the received signal is weak, a CW signal will "go through" more
clearly.
Per Erik Jorde
> That was a change of subject, but OK.....
[snip]
Paul, many thanks for your detailed information.
Chris L Peterson
wrote:
>More problematically: digital transmissions (TV or radio) have delays in
>them that makes the time signal unreliable. Where to get reliable
>time signals for time-critical observations (astrometry, occultation
>timings, etc.) from now on?
If you need to make time critical observations, you should be using GPS.
It's much more accurate than any of the radio time standards, and has a
much more widely accessible signal. GPS time receivers have become
fairly common and inexpensive (still a little more than a cheap radio
receiver, but not much).
Martin Brown
> In article <m3ps0xh86c....@pulsar.imr.no>,
> Per Erik Jorde <pe...@pulsar.imr.no> wrote:
>
> >pau...@saaf.se (Paul Schlyter) writes:
>
> >> ...except that VHF television is vanishing. In Sweden, the very last
> >> VHF TV transmitters will close down this fall - most of them already
> >> have closed down. After that, we only have digital UHF television.
> >> Other European countries are expected to do the same within a few
> >> years.
UK still has TV on analogue UHF and digital UHF co-existing. The
delays are significant and annoying on the digital TV and the new
audio quality is dubious. Live Proms classical concerts that were very
dynamic and involving on FM radio were lifeless and dead sounding on
digital TV broadcast (although the noise floor was lower).
> >time signals for time-critical observations (astrometry, occultation
> >timings, etc.) from now on?
>
> That was a change of subject, but OK.....
>
> We still have shortwave radio time signals. Here in Europe, Moscow
> transmits more or less continuously at 4996, 9996 and 14996 kHz - at
> least one of these frequencies can be heard any time of the day or
> night. This requires a shortwave receiver capable of reveicing CW
> or SSB though.
>
> And then you can get a radio controlled clock, which here in Europe
> is controlled by the transmitter in Mainflingeln, Germany, which
> transmits at (I believe) 77.5 kHz, i.e. in the LF band. I've
And Rugby MSF on 60 kHz in the UK. Although the German signal is
usable too.
> checked a few radio controlled clocks against time signals, and
> they agree "exactly" as far as my eye and ear could determine
> (which means any discrepancy is less than approx. 0.1 seconds).
We used Rugby MSF together with a local phase locked Rubidium clock
for low frequency VLBI a long time ago. There was a slight systematic
delay error in their CW seconds pulse rise time in the early morning
if the ground was wet with dew. It showed as a few hundred microsecond
drift when the sun burnt it off (from memory). When asked about it
they were surprised. They were also astonished that it could be
measured at all.
Consumer grade kit may have a small systematic delay in decoding the
signal and presenting it on the display. Likely to be at most 50ms or
so.
>
> Finally, if you want to be really "hi-tech", there are always the
> GPS satellites, which transmit time information to a very high
> accuracy. The typical GPS receiver units are pretty bad at displaying
> this time info at the right time though - there's a typical delay of
> some 1 to 2 seconds in the displayed time.
Most people using GPS want to know where they are...
Regards,
Martin Brown
laura halliday
wrote:
> > Finally, if you want to be really "hi-tech", there are always the
> > GPS satellites, which transmit time information to a very high
> > accuracy. The typical GPS receiver units are pretty bad at displaying
> > this time info at the right time though - there's a typical delay of
> > some 1 to 2 seconds in the displayed time.
>
> Most people using GPS want to know where they are...
It's not difficult to pick up surplus timing GPS receivers, like
the ones cell towers use. They provide an accurate
1 PPS signal, plus other data. Depending on the model and
the circumstances, the 1 PPS accuracy will be microseconds
to nanoseconds. If that's not accurate enough for you, I'm
not sure what will be. :-)
My timing sources include a WWVB clock, shortwave
receivers, GPS, my cellphone, and, if needed, a phone
call to the WWV and WWVH audio feeds (+1 303 499 7111
and +1 808 335 4363, respectively).
>From the west coast of Canada CHU is a tough signal,
but WWV and WWVH are fine most of the time. I used
to pick up VNG from Australia a lot, particularly in the
morning. One morning VNG was the strongest signal on
5 MHz, with WWVH in the background. I got two QSLs
for that one! VNG's other strong frequency was 8638 kHz,
right next to Korean station HLW on 8636 kHz.
Paul Schlyter
>> In article <m3ps0xh86c....@pulsar.imr.no>,
>> Per Erik Jorde <pe...@pulsar.imr.no> wrote:
>>
>> >pau...@saaf.se (Paul Schlyter) writes:
>>
>> >> ...except that VHF television is vanishing. In Sweden, the very last
>> >> VHF TV transmitters will close down this fall - most of them already
>> >> have closed down. After that, we only have digital UHF television.
>> >> Other European countries are expected to do the same within a few
>> >> years.
>
>UK still has TV on analogue UHF and digital UHF co-existing. The
>delays are significant and annoying on the digital TV and the new
>audio quality is dubious. Live Proms classical concerts that were very
>dynamic and involving on FM radio were lifeless and dead sounding on
>digital TV broadcast (although the noise floor was lower).
Is UHF TV (either analog or digital) useable for detecting meteor
showers?
True - however, accurate time is available through GPS - worldwide,
even if most users haven't discovered that yet.
>Regards,
>Martin Brown
Paul Schlyter
>wrote:
>
>>More problematically: digital transmissions (TV or radio) have delays in
>>them that makes the time signal unreliable. Where to get reliable
>>time signals for time-critical observations (astrometry, occultation
>>timings, etc.) from now on?
>
>If you need to make time critical observations, you should be using GPS.
>It's much more accurate than any of the radio time standards, and has a
>much more widely accessible signal. GPS time receivers have become
>fairly common and inexpensive (still a little more than a cheap radio
>receiver, but not much).
Can you give some examples of available and not that expensive
GPS time receivers?
>_________________________________________________
>
>Chris L Peterson
>Cloudbait Observatory
>http://www.cloudbait.com
Chris L Peterson
>Can you give some examples of available and not that expensive
>GPS time receivers?
I regularly see used GPS time bases (crystal oscillators with GPS
training) on sites that sell surplus equipment. Common prices are on the
order of US$200.
For my work, I use Garmin GPS18 modules, which run about $US80. But
there are a number of modular GPS units with 1pps outputs in that price
range.
To make use of the output, you can use a number of free or cheap
computer programs, use the 1pps signal directly on an audio track, or
use an OSD generator for video. A Kiwi OSD, for example, is just US$165.
David Knisely
> If you need to make time critical observations, you should be using GPS.
> It's much more accurate than any of the radio time standards, and has a
> much more widely accessible signal. GPS time receivers have become
> fairly common and inexpensive (still a little more than a cheap radio
> receiver, but not much).
I don't know about being much more accurate than *any* of the radio
time standards. WWV comes directly without any time delay, so it should
be quite accurate. Clear skies to you.
--
David W. Knisely KA0...@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/
**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************
Chris L Peterson
wrote:
>I don't know about being much more accurate than *any* of the radio
>time standards. WWV comes directly without any time delay, so it should
>be quite accurate. Clear skies to you.
WWV is generally accurate to the tens of millisecond range. To use it
well, you need to compensate for your distance from the transmitter as
well as for various atmospheric conditions.
GPS can be accurate to the nanosecond range, with inexpensive GPS
receivers normally guaranteeing their time output to better than one
microsecond.
GPS is definitely the way to go for critical timing applications (such
as timestamping individual video frames).
Paul Schlyter
>wrote:
>
>>I don't know about being much more accurate than *any* of the radio
>>time standards. WWV comes directly without any time delay, so it should
>>be quite accurate. Clear skies to you.
>
>WWV is generally accurate to the tens of millisecond range. To use it
>well, you need to compensate for your distance from the transmitter as
>well as for various atmospheric conditions.
>
>GPS can be accurate to the nanosecond range, with inexpensive GPS
>receivers normally guaranteeing their time output to better than one
>microsecond.
>
>GPS is definitely the way to go for critical timing applications (such
>as timestamping individual video frames).
Unless you have an extremely high video frame rate, the 10 ms accuracy
of WWV ought to be sufficient. At 30 frames/s there is some 33 ms
between each frame, and at 25 frames/s there is 40 ms between each
frame. No need for nanosecond accuracy here!
>_________________________________________________
>
>Chris L Peterson
>Cloudbait Observatory
>http://www.cloudbait.com
Paul Schlyter
David Knisely <KA0...@navix.net> wrote:
> Chris L. Peterson wrote:
>
>> If you need to make time critical observations, you should be using GPS.
>> It's much more accurate than any of the radio time standards, and has a
>> much more widely accessible signal. GPS time receivers have become
>> fairly common and inexpensive (still a little more than a cheap radio
>> receiver, but not much).
>
> I don't know about being much more accurate than *any* of the radio
> time standards. WWV comes directly without any time delay, so it should
> be quite accurate. Clear skies to you.
> --
> David W. Knisely KA0...@navix.net
> Prairie Astronomy Club: http://www.prairieastronomyclub.org
> Hyde Memorial Observatory: http://www.hydeobservatory.info/
A radio wave travels some 300 meters (1000 feet) in one microsecond.
So if you're closer than 300 meter to the nearest WWV transmitter, you
might be able to talk about "no delay". Most people have hundreds of
kilometers (or more) to the nearest WWV transmitter - which means the
radio wave propagation will cause a delay of hundreds of microseconds.
The radio waves from the GPS satellites will of course also need time
to propagate. But the GPS receiver will know the precise distance to
each satellite (otherwise it would be unable to figure out its precise
position), and is therefore able to compensate for this delay, giving
you a more precise time to an accuracy of one microsecond or so.
That's why GPS time is more accurate than any of the radio time signals.
Of course if you only need a modest time accuracy of some 100
milliseconds, then you can accept the delay from radio wave
propagation over 10,000 or 20,000 km without any problem. And 20,000
km, that's halfway around the globe.
Steve
laura halliday wrote:
> 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.
As Laura and others point out, all such definitions are somewhat
arbitrary, though I suppose the above is as good as any.
> 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.
If you define "radio" as employing _coherent_ detection, which I think
is what Laura is getting at here, then the limit 30 years ago was
about 3E13 Hz, i.e., 10 microns in the infrared. The limit today may
be higher; laboratory physics experiments have been done with higher
frequencies, but I'm not aware of any astronomical observations. The
technique is entirely radio-like: mix the incoming signal with a local
oscillator (laser in this case), then amplify and detect the beat
frequencies.
As others have written in response to the OP's additional query, none
of this has anything to do with amplitude modulation or sound.
Chris L Peterson
>Unless you have an extremely high video frame rate, the 10 ms accuracy
>of WWV ought to be sufficient. At 30 frames/s there is some 33 ms
>between each frame, and at 25 frames/s there is 40 ms between each
>frame. No need for nanosecond accuracy here!
With the ordinary video cameras used in my allsky network, a subframe
exposure (derived from a deinterlaced frame) is 16 ms. By interpolating
brightness, I can usually estimate the event start time to about 4 ms.
To eliminate any timing error, I therefore require my timestamp accuracy
to be about 2 ms, and I need that accuracy to be fixed (and my times
synchronized) across multiple stations separated by hundreds of
kilometers. What is actually recorded is the individual frame start and
stop times to an accuracy of 1 ms. I don't need the full microsecond
accuracy of my GPS clocks, but I need much better than I can easily get
with a radio standard.
Androcles
"Steve" <wil...@cfa.harvard.edu> wrote in message
news:1189027218.9...@d55g2000hsg.googlegroups.com...
:
I did a living room experiment with my TV's remote control,
it seems to be adequately modulated, changing channels,
raising and lowering sound, muting and so on quite reliably.
I expect laboratory physics experiments could do it at optical
frequencies if they really tried hard (defining radio as employing
_coherent_ detection, that is).
Andrew Smallshaw
There are a number of methods. The speaking clock is usually pretty
good. You appear to be in Norway, and while I'm not about it there,
it's good to within 5 ms from a landline here in the UK. That's
basically as accurate you're going to get unless you're timing things
automatically in some manner.
GPS will give you a precision time signal the world over.
Finally, in Norway you should be able to get decent ground-wave
reception of the MSF time/frequency signal broadcast from here in
the UK. Probably the German equivalent to, whose name I forget
right now. They can be obtained from fairly cheap radio-controlled
clocks. If you need better time accuracy than simply observing
the correct time yourself, it's relatively easy to decode these
signals automatically and connect that to whatever is recording
events.
--
Andrew Smallshaw
and...@sdf.lonestar.org
Greg
holds alot more text than in the old days, and people reply to specific
topics so the people already know what it's all about, and if I reply
to a specific question I'll quote that one ,so kill me :)
Actually (not complaining - just noting for those who don't know) you
can also receive single meteors entering the atmosphere,
not only meteor shower.
Tuning the SSB radio to a tv carrier far far away will give you a 'ping'
every time a meteor hits between you and the station, the farther away
the more pings you get.
http://www.gravitywell.org/misc/misc.htm
to show you what it sounds like (no I'm not a webdesigner either :)
To the best of my knowledge the station I'm tuned in on is in the baltic,
and I live in Sweden, so across the entire baltic sea I get to hear alot of
pings... I also have a feeling they'll continue using analogue tv for a while.
>> 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.
>
> ...except that VHF television is vanishing. In Sweden, the very last
> VHF TV transmitters will close down this fall - most of them already
> have closed down. After that, we only have digital UHF television.
> Other European countries are expected to do the same within a few
> years.
>
> And UHF signals don't reflect as well off sporadic E layes.
>
> --
> ----------------------------------------------------------------
> Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
> e-mail: pausch at stockholm dot bostream dot se
> WWW: http://stjarnhimlen.se/
//Greger
Project Argus station JO89sn
Bålsta - SWEDEN
Androcles
need to read what you said.
--
'we establish by definition that the "time" required by
light to travel from A to B equals the "time" it requires
to travel from B to A' because I SAY SO and you have to
agree because I'm the great genius, STOOOPID, don't you
dare question it. -- Rabbi Albert Einstein
http://www.androcles01.pwp.blueyonder.co.uk/Smart/tAB=tBA.gif
'we establish by definition that the "time" required by
light to travel from A to B doesn't equal the "time" it requires
to travel from B to A in the stationary system, obviously.' --
Heretic Jan Bielawski, assistant light-bulb changer.
Ref: news:1188363019....@k79g2000hse.googlegroups.com
"SR is GR with G=0." -- Uncle Stooopid.
The Uncle Stooopid doctrine:
http://sound.westhost.com/counterfeit.jpg
"What can be asserted without evidence can also be dismissed without
evidence." -- Uncle Stooopid.
"Counterfactual assumptions yield nonsense.
If such a thing were actually observed, reliably and reproducibly, then
relativity would immediately need a major overhaul if not a complete
replacement." -- Humpty Roberts.
Rabbi Albert Einstein in 1895 failed an examination that would
have allowed him to study for a diploma as an electrical engineer
at the Eidgenössische Technische Hochschule in Zurich
(couldn't even pass the SATs).
According to Phuckwit Duck it was geography and history that Einstein
failed on, as if Eidgenössische Technische Hochschule would give a
damn. That tells you the lengths these lying bastards will go to to
protect their tin god, but its always a laugh when they slip up.
Trolls, the lot of them.
"This is PHYSICS, not math or logic, and "proof" is completely
irrelevant." -- Humpty Roberts.
"Greg" <as...@gravitywell.org> wrote in message
news:2z9Ei.8119$ZA....@newsb.telia.net...
: Yes I think top-posting is the way to go these days, a normal PC screen
:
: