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What is the highest radio frequency used for radio astronomy?



 
 
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  #41  
Old September 4th 07, 09:12 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Paul Schlyter[_2_]
external usenet poster
 
Posts: 893
Default What is the highest radio frequency used for radio astronomy?

In article . com,
laura halliday 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.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
  #42  
Old September 5th 07, 10:20 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Steve
external usenet poster
 
Posts: 6
Default What is the highest radio frequency used for radio astronomy?


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.

  #43  
Old September 5th 07, 10:45 PM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Androcles[_2_]
external usenet poster
 
Posts: 1,040
Default What is the highest radio frequency used for radio astronomy?


"Steve" wrote in message
oups.com...
:
: 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.

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).





  #44  
Old September 7th 07, 11:17 AM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Greg[_3_]
external usenet poster
 
Posts: 3
Default What is the highest radio frequency used for radio astronomy?

Yes I think top-posting is the way to go these days, a normal PC screen
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


  #45  
Old September 7th 07, 11:20 AM posted to sci.astro.amateur,sci.astro,alt.astronomy,rec.radio.amateur.space,uk.sci.astronomy
Androcles[_2_]
external usenet poster
 
Posts: 1,040
Default What is the highest radio frequency used for radio astronomy?

The problem with top posting is the respondent doesn't actually
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.blueyonde...rt/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: ups.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 *******s 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" wrote in message
...
: Yes I think top-posting is the way to go these days, a normal PC screen
: 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
:
:


 




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