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

[John Smith I]

That has nothing to do with helping someone understand AM. It appears you
are more interested in dumping your blog on this board, than providing
something to clarify the real answers for an electronic novice.

So, you will decide what he needs to know and what he doesn't?

If he becomes aware of the more esoteric and trivial it is dangerous.

Get real control freak!

JS

 

[Don Bowey]

So, you will decide what he needs to know and what he doesn't?

If he becomes aware of the more esoteric and trivial it is dangerous.

Get real control freak!

JS

You really are thick headed if you can read Radium's posts and can't see how
he can't even deal with the real topic, much less the junk you toss in. The
more esoteric material should come after there is a grasp of the basics.

 

[John Smith I]

You really are thick headed if you can read Radium's posts and can't see how
he can't even deal with the real topic, much less the junk you toss in. The
more esoteric material should come after there is a grasp of the basics.

What, you have already given up on him and consigned him to a special
education class? Damn, I missed him being that dense, of course I tend
to give everyone the benefit of the doubt--even you ...

JS

 

[Jeff Liebermann]

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."

I beg to differ. My favorite mentor/instructor/employer had a
different philosophy regarding questions and answers. His line was
something like "If you don't understand the problem, no solution is
possible". His method was to concentrate on understanding the
problem, refining the corresponding questions, and only then
concentrating on finding the answer. I would spend much more time
thinking about "what problem am I trying to solve" instead of
blundering prematurely toward some potentially irrelevant solution.

My problem with the original question is that it fails to associate
itself with anything recognizable as a real problem to solve or a
theory to expound. In my never humble opinion, if there was a
question under all that rubbish, it was quite well hidden and severely
muddled. He also introduced a substantial number of "facts" that
varied from irrelevant to incoherent to just plain wrong. The problem
for us in not in finding the answer, but in decoding the question.

There may not be any stupid questions, but there seem to be a
substantial number of marginal people asking questions. I answer some
techy questions in alt.internet.wireless. What I see, all too often,
are people that seem to think that no effort on their part is
necessary to obtain an answer. They exert no effort to read the FAQ,
no effort to supply what problem they are trying to solve, and no
effort to supply what they have to work with. In this case, Mr Radium
has either exerted no effort to compose his question in a form that
can be answered, or if there was such an effort, it has failed
miserably. He couldn't even find a suitable collection of newsgroups
for his question.

There may not be any stupid questions, but there certainly are
questions not worth the time attempting to answer. If Mr Radium had
left the question at the subject line:
"AM electromagnetic waves: 20 KHz modulation frequency on
an astronomically-low carrier frequency"
the question would have been easy to answer, as several people have
done. However, those that answered and I all did the same thing. We
extracted from the word salad question what we thought was something
resembling a coherent question, and ignored the rest of the rubbish.
In other words, we did the necessary simplification and problem
reduction, and discarded the bulk of the incoherent residue. There
may not be any stupid questions, but if you bury it under a sufficient
number of words, it may closely resemble a stupid question.

Depends ... I guess.
JS

Well, let's see:
<http://groups.google.com/groups?as_q="guess(tm)"&as_uauthors=Jeff+Liebermann>
533 guesses, out of about 16,000 postings, which I guess(tm) isn't all
that bad.

 

[Don Bowey]

What, you have already given up on him and consigned him to a special
education class? Damn, I missed him being that dense, of course I tend
to give everyone the benefit of the doubt--even you ...

JS

As a matter of fact, as you should be able to see, I am working here in
support of his learning process while you do nothing but rag on in support
of your blog.

 

[John Smith I]

As a matter of fact, as you should be able to see, I am working here in
support of his learning process while you do nothing but rag on in support
of your blog.

idiot

JS

 

[Don Bowey]

idiot

JS

OK, you win.

 

[John Smith I]

[pure crap!]

"In the mid-1870s, a form of amplitude modulation—initially called
"undulatory currents"—was the first method to successfully produce
quality audio over telephone lines. Beginning with Reginald Fessenden's
audio demonstrations in the early 1900s, it was also the original method
used for audio radio transmissions, and remains in use by some forms of
radio communication—"AM" is often used to refer to the mediumwave
broadcast band (see AM radio)."

Taken from this URL: http://en.wikipedia.org/wiki/Amplitude_modulation

And, please read the WHOLE PAGE before making a larger idiot of yourself ...

JS

 

[Don Bowey]

[pure crap!]

"In the mid-1870s, a form of amplitude modulation‹initially called
"undulatory currents"‹was the first method to successfully produce
quality audio over telephone lines. Beginning with Reginald Fessenden's
audio demonstrations in the early 1900s, it was also the original method
used for audio radio transmissions, and remains in use by some forms of
radio communication‹"AM" is often used to refer to the mediumwave
broadcast band (see AM radio)."

Taken from this URL: http://en.wikipedia.org/wiki/Amplitude_modulation

And, please read the WHOLE PAGE before making a larger idiot of yourself ...

JS

I didn't read the link, as it has nothing to do with this string.

You posted to Radium's question about Amplitude Modulation, saying that on a
telephone line, the DC voltage is the Carrier and the microphone current (or
voltage if you prefer) is the modulation. Now THAT is un-pure crap and it
is what I responded to and which you deleted in this post hoping to look
better, which you don't.

I already conceded to your ignorance, so you really didn't need to post
more, but thanks for the opportunity to help.

 

[John Smith I]

[more crap!]

Oh, that explains it, your understanding of amplitude modulation is:

AM = Black Magic.

ROFLOL!

JS

 

[Radium]

radium, I applaud you in your interest generating discussion.

if there are no questions there are no answers; dumb or smart!

to me your questions came across wonderfully, and generated both
responses.

as humans we stand on two legs, most of us that is.

men get the honor and privilage to stand on three legs from time to
time.

this is our blessing and our curse!

Thanks for your understanding.

ps. how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
between frequencies of 40,000 to 285,000 Hz.

As I learned recently, 40 KHz is the minimum radio frequency required
to coherently transmit/receive audio signals. The highest sound a
human can hear is 20 KHz. The radio-frequency used must be at least 2x
the intended frequency of the information being transmitted/received.

I chose 285 KHz to be the highest radio frequency for cell-phones
because it is roughly the highest-frequency categorized as "long wave"
radio.

and your
discussion group of course!

You mean the anti-yahoo group?

http://groups.google.com/group/yahoo_stinks?lnk=li&hl=en

 

[Porgy Tirebiter]

On Jul 1, 7:24 am, [email protected] wrote:
Analog cells phones should stop using FM and should start using AM
between frequencies of 40,000 to 285,000 Hz.

I chose 285 KHz to be the highest radio frequency for cell-phones
because it is roughly the highest-frequency categorized as "long wave"
radio.

IDIOT!......complete idiot......

 

[John Fields]

Thanks for your understanding.


Analog cells phones should stop using FM and should start using AM
between frequencies of 40,000 to 285,000 Hz.

---
Good idea. The available spectrum between 40kHz and 285kHz is
245kHz wide, so at a little less than 3kHz per channel the maximum
number of channels available would be 82. That means that no more
than 82 people can be on the air at the same time.

Probably all over the world, to boot, what with those frequencies
being able to propagate over long distances.

That's probably a good thing, because with those 1875 meter long 1/4
wave whips at 40kHz and those 263 meter 1/4 wave whips at 285kHz on
the mobiles, any more people on the air than that would certainly
create a hazardous situation.

 

[Don Bowey]

[more crap!]

Oh, that explains it, your understanding of amplitude modulation is:

AM = Black Magic.

ROFLOL!

JS

OK you stupid shit, I'm almost out of patience with your ignorance. I was
hoping you might learn something, but I see that is unlikely.

AM is a process of frequency multiplication. Now you tell me where you
think such multiplication takes place on a phone line, and I'll follow-uo by
telling why you're full of crap.

SIMECS!

 

[Don Bowey]

Thanks for your understanding.


Analog cells phones should stop using FM and should start using AM
between frequencies of 40,000 to 285,000 Hz.

As I learned recently, 40 KHz is the minimum radio frequency required
to coherently transmit/receive audio signals. The highest sound a
human can hear is 20 KHz. The radio-frequency used must be at least 2x
the intended frequency of the information being transmitted/received.

I chose 285 KHz to be the highest radio frequency for cell-phones
because it is roughly the highest-frequency categorized as "long wave"
radio.


You mean the anti-yahoo group?

http://groups.google.com/group/yahoo_stinks?lnk=li&hl=en

Darn it Radium, you just hit a new low.

See that teeney antenna on cell phones? Just how well do you think it will
radiate 285 kHz?

 

[RHF]

- IDIOT!......complete idiot......

PT - Once again why waste your time replying
to his posts ? ? ? {Oops Like I Am Doing Too !}

Actually "Radium" would appear to be an
In-Complete-Want-To-Be driven by the 'urge'
to Post these Forever Ponding Questions
for others to charge at like Don Quijote's
quest to slay Windmills {a fool's errand}
http://en.wikipedia.org/wiki/Don_Quixote
http://en.wikipedia.org/wiki/Fool's_errand

FWIW - While many of his Post might fit into
the "sci.electronics.basics" NewsGroup; often
they would be consider OFF-TOPIC in other
NewsGroups like : rec.radio.shortwave,
rec.radio.amateur.antenna, alt.cellular.cingular,
alt.internet.wireless, etc

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

 

[Jeff Liebermann]

Analog cells phones should stop using FM and should start using AM
between frequencies of 40,000 to 285,000 Hz.

Analog cell phones are going to be history in the US on Feb 18, 2008.
Japan killed off analog around June 1999, Korea in Jan 2000, most of
Europe in 1997, etc.

40KHz thru 285Khz? Great idea. Just one minor problem. A 1/4 wave
antenna at about 100Khz frequency is 750 meters long. That's going to
be a rather large antenna for literally dragging behind you. Maybe a
balloon? Maybe a loop like this one?
<http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=10850>
Of course propagation might be a problem, as it will only work at
night and you'll have to connect to a cell site on the opposite coast
for those frequencies to work. The customers can be ignored when they
complain about atmospheric static and noise.

Of course, 240KHz of usable bandwidth is much less than the hundreds
of MHz currently in use by cellular providers, so there will
substantially fewer users. Let's see.... there are 240 million
subscribers in the US. Your AM system can handle about 40 users (6KHz
channels), so your cell phone bill will only be 6 million times larger
than it is currently. Now do you see why the microwave bands are so
in demand for cellular.

As I learned recently, 40 KHz is the minimum radio frequency required
to coherently transmit/receive audio signals.

Coherently? I would be worried if you planned to incoherently
transmit/receive audio signals. Perhaps if you added 40KHz to your
word salad, it would make your blather more coherent. (Hint: Look
up the definition of coherent and then use it where appropriate).

Actually, you're close. 40KHz is the common frequency used by
ultrasonic TV remote controls. I've seen PWM modulation system using
a pair of these to act as a crude cordless phone (that doesn't require
FCC type certification). You could probably go down to 20KHz, but
then intermodulation products (mixes) between the audio and the
carrier will begin to be a problem. Congratulations, you got one
thing mostly correct.

The highest sound a
human can hear is 20 KHz.

Voice is from 300 to 3000Hz. You could probably get away with 300 to
2400Hz. If you're planning to transmitting AM hi-fi or data, then you
might need the 20KHz.

The radio-frequency used must be at least 2x
the intended frequency of the information being transmitted/received.

Ummm... no. You're apparently thinking of the Shannon rule for
information bandwidth:
<http://en.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem>
If your input audio is perhaps bandwidth limited to 3KHz, a 6KHz
carrier will not work. You'll get considerable mixing (aliasing) and
audio intermodulation crud. The carrier would need to be somewhat
higher in frequency as limited by whatever output RF filtering is
used.

I chose 285 KHz to be the highest radio frequency for cell-phones
because it is roughly the highest-frequency categorized as "long wave"
radio.

Nope. See details at:
<http://en.wikipedia.org/wiki/Longwave>

 

[Don Bowey]

- IDIOT!......complete idiot......

PT - Once again why waste your time replying
to his posts ? ? ? {Oops Like I Am Doing Too !}

Actually "Radium" would appear to be an
In-Complete-Want-To-Be driven by the 'urge'
to Post these Forever Ponding Questions
for others to charge at like Don Quijote's
quest to slay Windmills {a fool's errand}
http://en.wikipedia.org/wiki/Don_Quixote
http://en.wikipedia.org/wiki/Fool's_errand

FWIW - While many of his Post might fit into
the "sci.electronics.basics" NewsGroup; often
they would be consider OFF-TOPIC in other
NewsGroups like : rec.radio.shortwave,
rec.radio.amateur.antenna, alt.cellular.cingular,
alt.internet.wireless, etc

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 a teacher MUST be rational. You rate Radium with more potential than I
can. This most recent post is really off the wall.

 

[Ron Baker, Pluralitas!]

In message <[email protected]>, cledus

I'm afraid that this is not correct. The 'laws of physics' don't suddenly
stop working if the carrier is lower than the modulating frequency.
However, there's no need to get into complicated mathematics to illustrate
this. Here is a simple example:

(a) If you modulate a 10MHz carrier with a 1MHz signal, you will produce
two new signals (the sidebands) at the difference frequency of 10 minus 1
= 9MHz, and the sum frequency of 10 plus 1 = 11MHz. So you have the
original carrier at 10MHz, and sideband signals at 9 and 11MHz (with a
balanced modulator - no carrier - only 9 and 11MHz).

(b) If you modulate a 1MHz carrier with a 10MHz signal, you will produce
two new signals (the sidebands) at the difference frequency of 1 minus 10
= minus 9MHz, and the sum frequency of 1 plus 10 = 11MHz. The implication
of the negative 'minus 9' MHz signal is that the phase of the 9MHz signal
is inverted, ie 180 degrees out-of-phase from 9MHz

Actually there would be no phase flip.
cos(-a) = cos(a)

produced in (a). So you have the original carrier at 1MHz, and sidebands
at 9 and 11MHz (again, with a balanced modulator - no carrier - only 9 and
11MHz).

The waveforms of the full composite AM signals of (a) and (b) will look
quite different. The carriers are at different frequencies, and the phase
of the 9MHz signal is inverted. However, with a double-balanced modulator,
you will only have the 9 and 11MHz signal so, surprisingly, the resulting
signals of (a) and (b) will look the same.

A double-balanced mixer is a multiplier. A * B = B * A

[Note that, in practice, many double-balanced modulators/mixers put loads
of unwanted signals - mainly due the effects of harmonic mixing. However,
the basic 'laws of physics' still apply.]

Finally, although I have spoken with great authority, when I get a chance
I WILL be doing at test with a tobacco-tin double-balanced mixer,

What's a tobacco-tin double-balanced mixer?

a couple of signal generators and a spectrum analyser - just to make sure
that I'm not talking rubbish. In the meantime, I'm sure that some will
correct me if I'm wrong.

You did pretty good.

 

[Tommy Tootles]

40KHz thru 285Khz? Great idea. Just one minor problem. A 1/4 wave
antenna at about 100Khz frequency is 750 meters long. That's going to
be a rather large antenna for literally dragging behind you.

Well, your math is correct. However, the so-called "atomic" wrist
watches receive their time signal from WWVB which transmits at 60kHz.

How do they get that 1250 meter long antenna ( 1/4 wave at 60 kHz)
inside that itty bitty wrist watch case? ;-)