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Sci.Electronics.Basics -> AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
There are 269 messages in this thread.
You are currently looking at messages 20 to 40.
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Author: JasenDate: 08:14 30-06-07
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["Followup-To:" header set to sci.electronics.basics.]
On 2007-06-30, John Smith I <assemblywizard@gmail.com> wrote:
> Radium wrote:
>
> WTF are you thinking when you describe the 20 Khz signal as, "a
> pure-sine-wave-tone] with a frequency of 20 KHz and an
> amplitude of 1-watt-per-meter-squared"
Candela
Admittedly an odd unit to use for radiation at that frequency.
Bye.
Jasen
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Author: JasenDate: 09:50 30-06-07
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Author: Porgy TirebiterDate: 13:14 30-06-07
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"Radium" is a well known "Troll".
When he runs low/out of meds and tin foil he will post this techo-babble
crap all over usenet.
Just add him to your killfile list.
"Radium" is a "Throw-away"....a complete waste of time......
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Author: RadiumDate: 15:46 30-06-07
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On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net> wrote:
> It is not possible to modulate a carrier frequency at a frequency higher
> than the carrier frequency.
Why not?
I am getting conflicting answers. Some say it's possible to modulate a
carrier frequency at a frequency higher than the carrier frequency,
others say it isn't.
Who is right?
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Author: John Smith IDate: 15:55 30-06-07
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Radium wrote:
> ...
> I am getting conflicting answers. Some say it's possible to modulate a
> carrier frequency at a frequency higher than the carrier frequency,
> others say it isn't.
>
> Who is right?
Radium:
Use simple logic, you can modulate a dc (0 Hz) with higher freq (voice),
(hint, your telephone line is an example) right?
However, when you get into RF--possible, usable, desirable are seperate
and distinct things.
Again, with simple logic, modulating a 30 CPS signal with limited voice
freq (say 5K wide) is going to create a LOT of harmonics and mixed
signals, ain't it? Suggesting a very wide band receiver would be needed
to begin with ... in my humble opinion, and for various reasons, NO, it
is NOT possible ...
Regards,
JS
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Author: RHFDate: 16:02 30-06-07
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On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net> wrote:
> "Radium" <gluceg...@gmail.com> wrote in message
>
> news:1183177831.152287.69850@j4g2000prf.googlegroups.com...
>
>
>
> > On Jun 29, 9:15 pm, John Smith I <assemblywiz...@gmail.com> wrote:
>
> > > Radium wrote:
>
> > > WTF are you thinking when you describe the 20 Khz signal as, "a
> > > pure-sine-wave-tone] with a frequency of 20 KHz and an
> > > amplitude of 1-watt-per-meter-squared"
>
> > > One square meter of copper wire squared, a squared meter of modulation
> > > xfrmr ... ?
>
> > Sorry that should be 1 X [10^-6] Watts-per-m^2
>
> >http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/sound/u11l2b.html
>
> > 1 X [10^-6] Watts-per-m^2 is about the loudness of a "normal
> > conversation" according to the above link.
>
> > F-------------------king typos!!!!!!!!!!
>
> > > Your question sounds like one of a high school physics student
> > > attempting to ask a seemingly logical--yet complex question, and of no
> > > real world value.
>
> > > Your ability at obfuscation is only mundane ...
>
> > > If what you say is true, you have an interest, what is the purpose of
> > > your question?
>
> > My basic question is if I have an AM receiver which receives signals
> > on a carrier frequency of Fc, is it mathematically-possible for me to
> > receive a modulator signal -- on that station -- of a frequency higher
> > than Fc? If not, then why? If not, then how are the submarines which
> > use ELFs [Extremely Low carrier Frequencies around 3 to 30 Hz] able to
> > perform voice communications?
>
> > I just stretched the question out to astronomical extremes. I have a
> > habit of doing that.
>
> Radium
>
> It is not possible to modulate a carrier frequency at a frequency higher
> than the carrier frequency. It wouldn't be a carrier frequency then, the
> higher frequency would become the carrier frequency by default.
>
> ELF communications are carried out at very slow data rates, only a few
> characters per hour at best. Normal demodulation techniques are useless at
> these frequencies and messages are received by what amounts to comparing the
> noise levels on a given very narrow frequency band over long periods.
> Computers are easily capable of performing this task. Messages are generally
> sent as 3 character codes which are then looked up in a code book to read
> the full text of the message. Each message can take half an hour or more to
> send. Only a very limited set of pre arranged messages can be passed but
> this is enough to tell a sub to approach the surface and establish line of
> sight comms direct to a satellite, when more detailed messages can be passed
> securely and at high speeds on higher frequencies (i.e voice and data
> communications). Voice comms cannot be passed at VLF or ELF frequencies.
>
> Nuclear subs are extremely autonomous. There is no quick way to establish
> communications once they have left port and submerged.
>
> It is possible to communicate at a base band frequency of 0Hz. This is what
> happens when you talk down a hard wired telephone or intercom. At a
> telephone exchange (switching centre), the signals from each line are
> modulated onto a higher frequency for onward transmission down a trunk wire
> cable or fibre optic cable. The multiplexed high frequency modulated signals
> are down converted back to audio frequencies once they reach the intended
> destination.
>
> It is also possible to transmit this signal through the air (at incredibly
> low efficiencies and powers). The miles of cables snaking through the
> trenches in World War One were so long that messages could be intercepted by
> the enemy listening in without any direct connection to the system. A good
> ground connection and half a mile of wire rolled out across no mans land was
> sufficient to pick up the signals from the other side. Systems were also
> discovered which employed two widely separated ground connections and
> avoided the need to send men out on a suicide mission to carry wires towards
> the enemy trenches.
>
> Mike G0ULI- Hide quoted text -
>
> - Show quoted text -
.
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Author: RHFDate: 16:02 30-06-07
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On Jun 30, 12:46 pm, Radium <gluceg...@gmail.com> wrote:
> On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net>
wrote:
>
> > It is not possible to modulate a carrier frequency at a frequency higher
> > than the carrier frequency.
>
> Why not?
>
> I am getting conflicting answers. Some say it's possible to modulate a
> carrier frequency at a frequency higher than the carrier frequency,
> others say it isn't.
>
> Who is right?
.
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Author: RHFDate: 16:03 30-06-07
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On Jun 30, 12:55 pm, John Smith I <assemblywiz...@gmail.com> wrote:
> Radium wrote:
>
> > ...
>
> > I am getting conflicting answers. Some say it's possible to modulate a
> > carrier frequency at a frequency higher than the carrier frequency,
> > others say it isn't.
>
> > Who is right?
>
> Radium:
>
> Use simple logic, you can modulate a dc (0 Hz) with higher freq (voice),
> (hint, your telephone line is an example) right?
>
> However, when you get into RF--possible, usable, desirable are seperate
> and distinct things.
>
> Again, with simple logic, modulating a 30 CPS signal with limited voice
> freq (say 5K wide) is going to create a LOT of harmonics and mixed
> signals, ain't it? Suggesting a very wide band receiver would be needed
> to begin with ... in my humble opinion, and for various reasons, NO, it
> is NOT possible ...
>
> Regards,
> JS
.
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Author: RHFDate: 16:03 30-06-07
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On Jun 30, 5:14 am, Jasen <j...@free.net.nz> wrote:
> ["Followup-To:" header set to sci.electronics.basics.]
> On 2007-06-30, John Smith I <assemblywiz...@gmail.com> wrote:
>
> > Radium wrote:
>
> > WTF are you thinking when you describe the 20 Khz signal as, "a
> > pure-sine-wave-tone] with a frequency of 20 KHz and an
> > amplitude of 1-watt-per-meter-squared"
>
> Candela
>
> Admittedly an odd unit to use for radiation at that frequency.
>
> Bye.
> Jasen
.
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Author: RHFDate: 16:16 30-06-07
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On Jun 30, 10:14 am, "Porgy Tirebiter" <bit...@gmail.com> wrote:
- "Radium" is a well known "Troll".
- When he runs low/out of meds and tin foil he will
- post this techo-babble crap all over usenet.
- Just add him to your killfile list.
- "Radium" is a "Throw-away"....a complete waste of time......
PT - Then why waste your time replying to his posts ?
IMHO - In another life "Radium" would have made
a great High School Science Teacher :
Who's Students when on to do great things with
their lives :
Because "Radium" Touched Them With A Thirst
For Knowledge And A Quest For Answers.
-but- These NewsGroups are NOT a High School
Science Class -and- "Radium" is just being 'radium'.
http://en.wikipedia.org/wiki/Radium
-alas- Our "Radium's" Half-Life of Readable Interest
http://en.wikipedia.org/wiki/Half-life
is at best about 16.04 Seconds ~ RHF
.
.
. .
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Author: Jim PenninoDate: 16:25 30-06-07
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In rec.radio.amateur.antenna Radium <glucegen1@gmail.com> wrote:
> On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net>
wrote:
> > It is not possible to modulate a carrier frequency at a frequency higher
> > than the carrier frequency.
> Why not?
> I am getting conflicting answers. Some say it's possible to modulate a
> carrier frequency at a frequency higher than the carrier frequency,
> others say it isn't.
> Who is right?
The defining equations, you blithering idtiot.
Here they are for the last time:
http://ccrma.stanford.edu/~jos/mdft/Sinusoidal_Amplitude_Modulation_AM.html
--
Jim Pennino
Remove .spam.sux to reply.
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Author: RHFDate: 16:25 30-06-07
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RADIUM,
IMHO - In another life "Radium" you would have
made a great High School Science Teacher :
Who's Students when on to do great things with
their lives :
Because You "Radium" Touched Them With A
Thirst For Knowledge And A Quest For Answers.
-but- These NewsGroups are NOT a High School
Science Class -and- "Radium" you are just being
'radium'. => http://en.wikipedia.org/wiki/Radium
decaying into a gas and dispersing into nothingness.
http://en.wikipedia.org/wiki/Radon
-alas- "Radium" Your Half-Life of Readable Interest
http://en.wikipedia.org/wiki/Half-life
is at best about 16.04 Seconds ~ RHF
.
.
. .
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Author: John Smith IDate: 16:34 30-06-07
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RHF wrote:
> ...
> Because "Radium" Touched Them With A Thirst
> For Knowledge And A Quest For Answers.
> ...
I don't know, according to any instructor I have ever had respect for:
"There are NO stupid questions, only stupid people who are afraid to ask
questions."
Depends ... I guess.
JS
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Author: Don BoweyDate: 16:38 30-06-07
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On 6/30/07 12:46 PM, in article
1183232774.691111.287830@o11g2000prd.googlegroups.com, "Radium"
<glucegen1@gmail.com> wrote:
> On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net>
wrote:
>
>> It is not possible to modulate a carrier frequency at a frequency higher
>> than the carrier frequency.
>
> Why not?
>
> I am getting conflicting answers. Some say it's possible to modulate a
> carrier frequency at a frequency higher than the carrier frequency,
> others say it isn't.
Partly it's because you formulate piss poor questions.
>
> Who is right?
>
Neither if stated as an "absolute rule," a.k.a. a Universal Generalization.
It depends on what you want as a result. However, IMHO opinion, I believe
it is best to have the Carrier at a higher frequency than the modulating
frequency.
If you are amplitude modulating a Carrier with a voice band signal, then it
is mandatory, for a reasonable result, that the Carrier have a much higher
frequency than the modulating frequency.
If you are AM modulating (a.k.a. RF mixing or converting) two signals for
the purpose of creating sum and difference "Carriers" in, for example, a
synthesizer, you could use the low frequency to "modulate" the high
frequency frequency, but I donšt recommend it unless some special effect is
desired.
Start with the question of what is it you wish to accomplish then ask real
questions, not some far-out hypothetical drivel.
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Author: RHFDate: 16:44 30-06-07
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On Jun 30, 1:38 pm, Don Bowey <dbo...@comcast.net> wrote:
> On 6/30/07 12:46 PM, in article
> 1183232774.691111.287...@o11g2000prd.googlegroups.com, "Radium"
>
> <gluceg...@gmail.com> wrote:
> > On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net>
wrote:
>
> >> It is not possible to modulate a carrier frequency at a frequency high=
er
> >> than the carrier frequency.
>
> > Why not?
>
> > I am getting conflicting answers. Some say it's possible to modulate a
> > carrier frequency at a frequency higher than the carrier frequency,
> > others say it isn't.
>
> Partly it's because you formulate piss poor questions.
>
>
>
> > Who is right?
>
> Neither if stated as an "absolute rule," a.k.a. a Universal
Generalizatio=
n=2E
> It depends on what you want as a result. However, IMHO opinion, I believe
> it is best to have the Carrier at a higher frequency than the modulating
> frequency. =20
>
> If you are amplitude modulating a Carrier with a voice band signal, then =
it
> is mandatory, for a reasonable result, that the Carrier have a much higher
> frequency than the modulating frequency.
>
> If you are AM modulating (a.k.a. RF mixing or converting) two signals for
> the purpose of creating sum and difference "Carriers" in, for example, a
> synthesizer, you could use the low frequency to "modulate" the high
> frequency frequency, but I don=B9t recommend it unless some special effec=
t is
> desired.
>
> Start with the question of what is it you wish to accomplish then ask real
> questions, not some far-out hypothetical drivel.
=2E
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Author: Mike KaliskiDate: 16:54 30-06-07
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"Radium" <glucegen1@gmail.com> wrote in message
news:1183232774.691111.287830@o11g2000prd.googlegroups.com...
> On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net>
wrote:
>
> > It is not possible to modulate a carrier frequency at a frequency higher
> > than the carrier frequency.
>
> Why not?
>
> I am getting conflicting answers. Some say it's possible to modulate a
> carrier frequency at a frequency higher than the carrier frequency,
> others say it isn't.
>
> Who is right?
>
Radium
Me
Read my entire earlier reply. Then go to the library and spend several years
reading through the electronics section with particular emphasis on the
origins of electrical technology and early wireless. Then take a technical
biased university course incorporating logic and critical analysis and all
will become clear.
Without a basic knowledge of the subject, you are unable to make any form of
critical judgement as to the accuracy or correctness of what people are
telling you and all your questions become valueless because you do not have
the nous to evaluate the answers you receive.
Start with the basics and then try working up from there. Many inadvisable
things are technically possible, putting a dead short across the mains will
generate a pretty good example of electromagnetic pulse, but it is far
better to use a capacitive discharge circuit to do the same job. You could
try modulating carriers at all different sorts of frequencies to generate
harmonics, far better to use a square wave generator. You get the idea.
Regards
Mike G0ULI
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Author: Jeff LiebermannDate: 18:46 30-06-07
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Radium <glucegen1@gmail.com> hath wroth:
>On Jun 30, 3:32 am, "Mike Kaliski" <michael.kali...@tesco.net>
wrote:
>
>> It is not possible to modulate a carrier frequency at a frequency higher
>> than the carrier frequency.
>
>Why not?
Unfortunately, this is a good question and literally the first and
probably only good question you've asked so far. Yes, it's possible,
but you won't get the results you're expecting. See below.
>I am getting conflicting answers. Some say it's possible to modulate a
>carrier frequency at a frequency higher than the carrier frequency,
>others say it isn't.
>
>Who is right?
What does my politics have to do with anything? For what it's worth,
I'm politically somewhat left of center on most of my views.
An AM modulator is just a simple multiplier (mixer). The modulator
takes two signals, multiplies (or mixes) them together, and produces
an amplitude modulated output. For one of about 10 assorted JAVA
applets Google found that illustrate the waveforms see:
<http://cnyack.homestead.com/files/modulation/modam.htm>;
Lots more at:
<http://www.educypedia.be/electronics/javamodulation.htm>;
Note that a simple multiplier (mixer) doesn't care which frequency is
the carrier and which is the modulation. The two input ports are
essentially identical. The carrier is always higher in fequency than
the modulation input. If your derranged experiment somehow causes the
modulation input frequency to exceed the carrier frequency, the
multiplier produces exactly the same output as if the frequencies were
reversed. The modulation frequency becomes the carrier, and the
carrier frequency becomes the modulation input. In other words, with
AM it doesn't matter which input is the higher frequency, the output
is exactly the same.
If you happen to own some audio test equipment, you can easily
demonstrate this with two audio oscillators, a mixer of some sorts,
and an oscilloscope. Setup the equipment with two different input
frequencies and look at the output waveform. Now, swap inputs and
look again. It's the same. There's no question of which input is
modulating which other input. With AM, it's ALWAYS the high frequency
that acts as the carrier and the lower that acts as the modulation.
Now, please go back to your cave and read something on the basics of
modulation. If words confuse you, see the above JAVA applets which
will do it with pictures.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Author: cledusDate: 20:53 30-06-07
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Radium wrote:
> Hi:
>
> Please don't be annoyed/offended by my question as I decreased the
> modulation frequency to where it would actually be realistic.
>
> I have a very weird question about electromagnetic radiation,
> carriers, and modulators.
>
> Is it mathematically-possible to carry a modulator signal [in this
> case, a pure-sine-wave-tone] with a frequency of 20 KHz and an
> amplitude of 1-watt-per-meter-squared on a AM carrier signal whose
> frequency is 10^-(1,000,000,000-to-the-power-10^1,000,000,000)
> nanocycle* every 10^1,000,000,000-to-the-power-10^1,000,000,000 giga-
> eons and whose amplitude is a minimum of 10^1,000,000,000-to-the-
> power-10^1,000,000,000 gigaphotons per 10^-(1,000,000,000-to-the-
> power-10^1,000,000,000) nanosecond?
>
> If it is not mathematically-possible, then please explain why.
>
> 10^-(1,000,000,000-to-the-power-10^1,000,000,000) second is an
> extremely short amount of time. 10^-(1,000,000,000-to-the-
> power-10^1,000,000,000) nanosecond is even shorter because a
> nanosecond is shorter than a second.
>
> Giga-eon = a billion eons
>
> Eon = a billion years
>
> *nanocycle = billionth of a cycle
>
> Gigaphoton = a billion photons
>
> 10^1,000,000,000-to-the-power-10^1,000,000,000 -- now that is one
> large large number.
>
> 10^1,000,000,000 = 10-to-the-power-1,000,000,000
>
> So you get:
>
> (10-to-the-power-1,000,000,000) to the power (10-to-the-
> power-1,000,000,000)
>
> 10^-(1,000,000,000-to-the-power-10^1,000,000,000) = 10^-(10-to-the-
> power-1,000,000,000)-to-the-power-(10-to-the-power-1,000,000,000)
>
> 10^-(10-to-the-power-1,000,000,000) to the power (10-to-the-
> power-1,000,000,000) is an extremely small number at it equals 10-to-
> the-power-NEGATIVE-[(10-to-the-power-1,000,000,000) to the power (10-
> to-the-power-1,000,000,000)]
>
> No offense but please respond with reasonable answers & keep out the
> jokes, off-topic nonsense, taunts, insults, and trivializations. I am
> really interested in this.
>
>
> Thanks,
>
> Radium
>
The fundamental answer is no, it is not possible to generate AM where
the baseband signal is a pure 20 kHz sinewave and Fc<20kHz. The reason
is that the modulated waveform consists of the sum of a sinewave at Fc,
a sinewave at Fc+20kHz, and a sinewave at Fc-20kHz. If Fc<20kHz then
one of the components becomes a "negative" frequency. So the carrier
must be greater than the baseband signal to prevent this.
It is conceivable that you could make Fc a miniscule number higher than
20kHz. However, if you want to radiate the signal efficiently, you will
need an antenna that is miles long. That is why most radios operate
with carrier frequencies much higher than the audio range. Antennas
become much more practical at frequencies in the MHz range.
You might enjoy a good book that provides fundamentals of electronics
and radio. Pick up a copy of the ARRL Handbook (www.arrl.org), for
example. That should help you pick up some of these concepts.
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Author: RadiumDate: 22:01 30-06-07
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On Jun 30, 3:46 pm, Jeff Liebermann <j...@cruzio.com> wrote:
>With AM, it's ALWAYS the high frequency
>that acts as the carrier
>and the lower that acts as the modulation.
In AM, isn't the carrier the signal which always maintains a constant
frequency and only varies by amplitude?
If a carrier signal varies by anything other than just amplitude, then
it isn't AM. Right?
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Author: John Smith IDate: 22:31 30-06-07
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Radium wrote:
> ...
> If a carrier signal varies by anything other than just amplitude, then
> it isn't AM. Right?
>
Let logic be your guide, again. As was pointed out earlier, the voice
freqs which modulate the carrier will cause a variance in freq (a small
fm component.)
In fm, it is not unusual for a small "amplitude modulation" to be
generated, as the varying/spanning of freq(s) is caused by the
modulation, some changes in fm carrier can be generated.
In an imperfect world, nothing is "perfect."
Regards,
JS
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