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Sci.Electronics.Basics -> radio transmissions at the frequency of light
There are 21 messages in this thread.
You are currently looking at messages 1 to 20.
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Author: jjoensuuDate: 21:39 16-01-07
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Hi all,
just wanted to ask, what would be the problems that make it
difficult/impossible to build a radio that transmits at the frequency
of visible light (between 430 and 750 Tera Hz)?
I guess one of them is that it is not possible for a regular coil
(copperwire around an air core) could not vibrate at that rate?
And here's another question: is it possible to build a radio
transmitter without a coil?
thanks in advance,
JJ
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Author: John LarkinDate: 22:12 16-01-07
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On 16 Jan 2007 18:39:27 -0800, "jjoensuu" <j_joensuu@yahoo.com> wrote:
>Hi all,
>
>just wanted to ask, what would be the problems that make it
>difficult/impossible to build a radio that transmits at the frequency
>of visible light (between 430 and 750 Tera Hz)?
>
Radio waves at the frequency of light *is* light.
>I guess one of them is that it is not possible for a regular coil
>(copperwire around an air core) could not vibrate at that rate?
Nope. The antenna size is about the diameter of an atom. The best
antenna *is* an atom.
>
>And here's another question: is it possible to build a radio
>transmitter without a coil?
Yup. Laser.
John
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Author: Sjouke BurryDate: 22:14 16-01-07
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jjoensuu wrote:
> Hi all,
>
> just wanted to ask, what would be the problems that make it
> difficult/impossible to build a radio that transmits at the frequency
> of visible light (between 430 and 750 Tera Hz)?
>
Its very easy to do, just modulate a led or laser,
and you have an AM transmitter, and if you whish
it, also a very narrow transmission beam.
Also, a choice of transmission frequencies is available,
from infrared to UV lasers.
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Author: Stephen J. RushDate: 23:26 16-01-07
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On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>>And here's another question: is it possible to build a radio
>>transmitter without a coil?
>
> Yup. Laser.
There are also designs that use cavity or transmission-line resonators.
These work at frequencies too low for lasers and masers, although they
get a bit bulky below UHF.
The lowest imaginable frequency is the one for which the universe
(assuming that spacetime is closed; the jury is still out) is a
resonant cavity.
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Author: Michael BlackDate: 23:50 16-01-07
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"Stephen J. Rush" (sjrush@comcast.net) writes:
> On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>
>>>And here's another question: is it possible to build a radio
>>>transmitter without a coil?
>>
>> Yup. Laser.
>
> There are also designs that use cavity or transmission-line resonators.
> These work at frequencies too low for lasers and masers, although they
> get a bit bulky below UHF.
>
I couldn't figure out whether he was asking that in reference to radio
light frequencies, or if it was just a general question.
Obviously one can live without coils in a transmitter, even where they'd
otherwise be the norm. But, you'd either end up with a lousy transmitter,
or one that is pretty low powered.
For instance, one could use crystals or ceramic resonators (or even
ceramic filters) as frequency selective elements, but they sure aren't
useable at high power levels. And if you put them before the output
stage, then you risk issuing spurious signals generated in that later
or those later stages.
A power crystal oscillator isn't completely uncommon, but again they
tended to put a coil in the output. If you can live with instability,
or a low enough frequency, and lots of harmonics, the power oscillator
could be controlled by a resistor and capacitor, basically a multivibrator,
and thus live without coils. But I'd not want to try to listen near that
transmitter, and it wouldn't be long before some regulator official came
knocking to complain.
Michael
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Author: John LarkinDate: 00:11 17-01-07
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On Tue, 16 Jan 2007 23:26:18 -0500, "Stephen J. Rush"
<sjrush@comcast.net> wrote:
>On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>
>>>And here's another question: is it possible to build a radio
>>>transmitter without a coil?
>>
>> Yup. Laser.
>
>There are also designs that use cavity or transmission-line resonators.
>These work at frequencies too low for lasers and masers, although they
> get a bit bulky below UHF.
>
>The lowest imaginable frequency is the one for which the universe
>(assuming that spacetime is closed; the jury is still out) is a
>resonant cavity.
A spinning magnet is a radio transmitter.
John
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Author: EeyoreDate: 01:44 17-01-07
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jjoensuu wrote:
> Hi all,
>
> just wanted to ask, what would be the problems that make it
> difficult/impossible to build a radio that transmits at the frequency
> of visible light (between 430 and 750 Tera Hz)?
There no problems.
Signalling using light is a well established technology.
Graham
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Author: jasenDate: 03:22 17-01-07
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On 2007-01-17, jjoensuu <j_joensuu@yahoo.com> wrote:
> Hi all,
>
> just wanted to ask, what would be the problems that make it
> difficult/impossible to build a radio that transmits at the frequency
> of visible light (between 430 and 750 Tera Hz)?
>
> I guess one of them is that it is not possible for a regular coil
> (copperwire around an air core) could not vibrate at that rate?
>
> And here's another question: is it possible to build a radio
> transmitter without a coil?
like a laser?
Bye.
Jasen
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Such as in a laser listening device. How about fiber optics.
On Jan 16, 10:14 pm, Sjouke Burry <burrynulnulf...@ppllaanneett.nnlll>
wrote:
> jjoensuu wrote:
> > Hi all,
>
> > just wanted to ask, what would be the problems that make it
> > difficult/impossible to build a radio that transmits at the frequency
> > of visible light (between 430 and 750 Tera Hz)?Its very easy to do, just
modulate a led or laser,
> and you have an AM transmitter, and if you whish
> it, also a very narrow transmission beam.
> Also, a choice of transmission frequencies is available,
> from infrared to UV lasers.
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Author: Bob MyersDate: 13:10 17-01-07
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Author: John FieldsDate: 17:31 17-01-07
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On Tue, 16 Jan 2007 23:26:18 -0500, "Stephen J. Rush"
<sjrush@comcast.net> wrote:
>On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>
>>>And here's another question: is it possible to build a radio
>>>transmitter without a coil?
>>
>> Yup. Laser.
>
>There are also designs that use cavity or transmission-line resonators.
>These work at frequencies too low for lasers and masers, although they
> get a bit bulky below UHF.
>
>The lowest imaginable frequency is the one for which the universe
>(assuming that spacetime is closed; the jury is still out) is a
>resonant cavity.
---
Not true. I can imagine one for a universe twice as large as ours.
--
JF
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Author: Bob MyersDate: 19:27 17-01-07
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"John Fields" <jfields@austininstruments.com> wrote in message
news:tr8tq2djerhuomhn58ustc9s8nng60onn3@4ax.com...
>>The lowest imaginable frequency is the one for which the universe
>>(assuming that spacetime is closed; the jury is still out) is a
>>resonant cavity.
>
> ---
> Not true. I can imagine one for a universe twice as large as ours.
Boy, I sure can't. Try as I might, I just can't
imagine one much bigger than about 1.75 times
ours...:)
Bob M.
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Author: Rich GriseDate: 20:18 17-01-07
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On Wed, 17 Jan 2007 18:10:19 +0000, Bob Myers wrote:
> "John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
>>
>> A spinning magnet is a radio transmitter.
>
> Really? Where does the electric field component come
> from?
>
The movement of the magnetic field, of course. You just haven't heard them
because nobody yet knows how to spin a magnet at 33,000,000 RPM. ;-)
Without coils, that is. ;-)
Cheers!
Rich
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Author: Rich GriseDate: 20:19 17-01-07
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On Wed, 17 Jan 2007 14:31:44 -0800, John Fields wrote:
> On Tue, 16 Jan 2007 23:26:18 -0500, "Stephen J. Rush"
>>On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>>
>>>>And here's another question: is it possible to build a radio
>>>>transmitter without a coil?
>>>
>>> Yup. Laser.
>>
>>There are also designs that use cavity or transmission-line resonators.
>>These work at frequencies too low for lasers and masers, although they
>> get a bit bulky below UHF.
>>
>>The lowest imaginable frequency is the one for which the universe
>>(assuming that spacetime is closed; the jury is still out) is a
>>resonant cavity.
>
> Not true. I can imagine one for a universe twice as large as ours.
What's kewl is to imagine a universe that's actually infinite, so the
lowest freq. is DC.
Of course, then we're left with the polarity question. ;-)
Cheers!
Rich
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Author: terryDate: 04:15 18-01-07
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jjoensuu wrote:
> Hi all,
>
> (1) just wanted to ask, what would be the problems that make it
> difficult/impossible to build a radio that transmits at the frequency
> of visible light (between 430 and 750 Tera Hz)?
>
> (2) I guess one of them is that it is not possible for a regular coil
> (copper wire around an air core) could not vibrate at that rate?
>
> (3) And here's another question: is it possible to build a radio
> transmitter without a coil?
>
> thanks in advance,
>
> JJ
.
1) Use a bulb or an LED or laser.
2) A 'coil' can be anything tha has inductance including, for example,
a short strip of copper on a circuit board a few millimetres or even a
few microns long. That is why leads are kept so short and components
small, in very high frequency equipment.
3) Yes: A magnetron does not have 'coils' in the conventional sense. It
generates microwave energy in an oscillatory chamber within an intense
magnetic field.
BTW are these answers for a test or exam?
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Author: Don BoweyDate: 12:16 18-01-07
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On 1/17/07 2:31 PM, in article tr8tq2djerhuomhn58ustc9s8nng60onn3@4ax.com,
"John Fields" <jfields@austininstruments.com> wrote:
> On Tue, 16 Jan 2007 23:26:18 -0500, "Stephen J. Rush"
> <sjrush@comcast.net> wrote:
>
>> On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>>
>>>> And here's another question: is it possible to build a radio
>>>> transmitter without a coil?
>>>
>>> Yup. Laser.
>>
>> There are also designs that use cavity or transmission-line resonators.
>> These work at frequencies too low for lasers and masers, although they
>> get a bit bulky below UHF.
>>
>> The lowest imaginable frequency is the one for which the universe
>> (assuming that spacetime is closed; the jury is still out) is a
>> resonant cavity.
Isn't that around 1.2 GHz.?
>
> ---
> Not true. I can imagine one for a universe twice as large as ours.
>
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Author: Grostle NewsDate: 07:28 19-01-07
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Author: Rich GriseDate: 17:43 31-01-07
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On Thu, 18 Jan 2007 09:16:05 -0800, Don Bowey wrote:
> "John Fields" <jfields@austininstruments.com> wrote:
>> On Tue, 16 Jan 2007 23:26:18 -0500, "Stephen J. Rush"
>>> On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>>>
>>>>> And here's another question: is it possible to build a radio
>>>>> transmitter without a coil?
>>>>
>>>> Yup. Laser.
>>>
>>> There are also designs that use cavity or transmission-line resonators.
>>> These work at frequencies too low for lasers and masers, although they
>>> get a bit bulky below UHF.
>>>
>>> The lowest imaginable frequency is the one for which the universe
>>> (assuming that spacetime is closed; the jury is still out) is a
>>> resonant cavity.
>
> Isn't that around 1.2 GHz.?
>
Huh? Got a universe in your pocket? ;-)
Given the size of the "known" universe, about 12,000,000,000 light-
years, the frequency at which it's a resonant cavity would be,
lessee, say a full-wave cavity, just for the sake of discussion,
12,000,000,000 lightyears = 1.13526341 × 10e26 meters
so at 300,000,000 m/sec, that'd give you, um...
2.642558523047968224e-18 Hz.
Cheers!
Rich
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Author: Don BoweyDate: 21:22 31-01-07
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On 1/31/07 2:43 PM, in article pan.2007.01.31.22.43.59.809609@example.net,
"Rich Grise" <rich@example.net> wrote:
> On Thu, 18 Jan 2007 09:16:05 -0800, Don Bowey wrote:
>> "John Fields" <jfields@austininstruments.com> wrote:
>>> On Tue, 16 Jan 2007 23:26:18 -0500, "Stephen J. Rush"
>>>> On Tue, 16 Jan 2007 19:12:45 -0800, John Larkin wrote:
>>>>
>>>>>> And here's another question: is it possible to build a radio
>>>>>> transmitter without a coil?
>>>>>
>>>>> Yup. Laser.
>>>>
>>>> There are also designs that use cavity or transmission-line resonators.
>>>> These work at frequencies too low for lasers and masers, although they
>>>> get a bit bulky below UHF.
>>>>
>>>> The lowest imaginable frequency is the one for which the universe
>>>> (assuming that spacetime is closed; the jury is still out) is a
>>>> resonant cavity.
>>
>> Isn't that around 1.2 GHz.?
>>
>
> Huh? Got a universe in your pocket? ;-)
Sure, doesn't everyone? I was probably thinking of the big-bang noise. Or
maybe I wasn't uhhhhhhhh.......
Don
>
> Given the size of the "known" universe, about 12,000,000,000 light-
> years, the frequency at which it's a resonant cavity would be,
> lessee, say a full-wave cavity, just for the sake of discussion,
>
> 12,000,000,000 lightyears = 1.13526341 × 10e26 meters
> so at 300,000,000 m/sec, that'd give you, um...
> 2.642558523047968224e-18 Hz.
>
> Cheers!
> Rich
>
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Author: Bob MyersDate: 18:10 01-02-07
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