# AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency

Discussion in 'Electronic Basics' started by Radium, Jun 30, 2007.

Hi:

Please don't be annoyed/offended by my question as I decreased the
modulation frequency to where it would actually be realistic.

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,

2. ### John Smith IGuest

The 20 Khz is obviously NOT an audio tone, but exists as VLF, what you
are terming "modulation" is actually a mixing of carriers then ... and
the problem with your question ONLY BEGINS there!

JS

3. ### craigmGuest

If you look at the math pertaining to modulation, there are no terms that
limit the frequencies used. So mathematically, you should be able to figure
it out yourself if it is possible.

You don't ask if it is physically possible, or if the results may be of any
use.

You don't want ridicule, but give no indication why this may be important to
you. (If you did, the responses may be more appropriate.)

You seem to be more interested as a troll.

Yes it is. 20 KHz is the highest audible frequency. Humans hear from
20 to 20,000 Hz. No offense but WTF are you thinking??
A carrier wave is modulated by the modulator wave. On most AM
stations, the modulator wave consists of the voice of someone
speaking.

Most AM stations have carrier frequencies in the medium wave band - in
the range of 520,000 to 1,160,000 cycles every 1 second.

In the case I am describing, the modulator wave is a 20 KHz pure sine-
wave tone on a carrier frequency of 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. Is this scenario mathematically-
possible? If not, then why??

5. ### John Smith IGuest

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 ... ?

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

JS

6. ### Don BoweyGuest

No, it's not possible. No planetary system will exist for that span of
time.

Now will you go away?

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!!!!!!!!!!
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.

8. ### Guest

The fact that you specified the modulation in W/M^2 immediately
says you don't know WTF you are talking about and the question
is meaningless.

You can AM modulate any frequency 0 < Fc < infinity with any other
frequency 0 < Fm < infinity.

Whether it's physically possible or results in massive distortion
is a separate issue.

<snip inane crap>

9. ### Don BoweyGuest

What is the design bandwidth of the "fixed frequency" receiver?

When you say "modulator signal" do you mean a sideband of the transmitted
signal, or do you mean at least one sideband and the Carrier, or do you mean
the Carrier and both of it's sidebands?

It would be good if you would attempt to understand AM modulation, and
generally some of the factors of receiver design.
Why do you believe they use voice communications on the ELF system?
You have a habit of appearing to be an idiot each time you do it.

10. ### Bob MyersGuest

Why not simply ask the question you mean to ask, then, rather
than the absurd numbers you put in the original version of this
(and which you then expect everyone to work through, just to
see what the hell you might be talking about)?

The answer to the question you seem to be asking is obvious
if you simply work through the mathematics of what is going on
in amplitude modulation. So why not simply do that, and not

One hint: the ELF submarine communications to which you refer
are NOT carrying voice communications, but very low-rate
CW ("Morse code," if you want to think of it that way) signalling.

Bob M.

13. ### Mike KaliskiGuest

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

Candela

Bye.
Jasen

oops, wrong.

Bye.
Jasen

16. ### Porgy TirebiterGuest

"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.
"Radium" is a "Throw-away"....a complete waste of time......

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?

18. ### John Smith IGuest

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