Re: sinusoidal carrier

[Jeff Liebermann]

karthikbalaguru <karthikbalaguru79@gmail.com> hath wroth:

>Is there any specific reason for most of the modulation technique to
>use sinusoidal carrier for modulation in wireless communication ? I
>searched the internet, but, did not get any specific link for this ?

I seem to be doing your homework. This is also the wrong newsgroup
for basic communications questions. Any book on basic communications
theory will have a page on waveform analysis.

You start with a sine wave. It's strictly the fundamental with no
harmonics.

If you add distorition (harmonics), if the harmonics are odd order
(3,5,7,9,11,etc), then the waveform will be symmetrical.

If you add distortion (harmonics), if the harmonics are even order
(2,4,6,8,10, etc), then the waveform will by asymmetrical.

Exmaples:
http://en.wikipedia.org/wiki/Sine_wave
http://en.wikipedia.org/wiki/Triangle_wave
http://en.wikipedia.org/wiki/Sawtooth_wave
http://en.wikipedia.org/wiki/Square_wave

If you spend some time with a function generator and spectrum
analyzer, you can see the effects of odd and even harmonics on
spectra.

If you want to use a computer to see how it works, I suggest you
download Sillanumsoft Visual Analyzer. This is a very handy audio
oscilloscope, spectrum analyzer, and function generator. You can
internally generate a waveform, and see the resulting spectra.
<http://www.sillanumsoft.org>
Don't forget to click the "ON" button in the upper left corner.

There are lots of other reasons to use a sine wave to drive a cell
phone. In order to get sufficient bits per baud, most modulation
methods involve both FM and AM. FM modulation doesn't care about the
harmonic content of the synthesizer. AM modulators care and will
produce distorted and non-linear garbage if overdriven by harmonic.

In addition, the FCC and other regulatory agencies fail to appreciate
harmonics and spurious signals being belched by cell phones. If you
remove the modulation, the remaining RF carrier needs to be about
clean down to about 0.0001% (about -60dB below peak power) in order to
placate the regulatory agency. If you can see the distortion, it will
fail.


--
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

[Larry]

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:13iln31j8t4hptd4d9pfkd7ed04i742bjf@4ax.com:

> There are lots of other reasons to use a sine wave to drive a cell
> phone. In order to get sufficient bits per baud, most modulation
> methods involve both FM and AM. FM modulation doesn't care about the
> harmonic content of the synthesizer. AM modulators care and will
> produce distorted and non-linear garbage if overdriven by harmonic.
>

Isn't it amazing the number of "digital generation" people you meet that
have no concept that you cannot transmit data, directly, over-the-air or
over long distances, without converting it into the analog world as
modulation. I've even had college kids in electronic engineering question
me about why data was "encoded" by some kind of modem for transmission.

They're ALL convinced their digital SELLphones are all data, not converted
into 8K or 11K samples for the phase modulated transmitters...

73 DE W4CSC

Jeff, I noticed your sig on usenet with all your Skype and phone numbers on
it. Doesn't that create a storm of crank/hate calls from the nutcases on
here? If not, I'm amazed. I know the spambots will storm email. I had to
get rid of myhamcall@myisp over it.

Larry
--
One of my neighbors is a very-well-educated person. He thinks TV DATA
comes in over the new DIGITAL TV antenna....(c; How broadband would that
be??....(c;

[Jeff Liebermann]

Larry <noone@home.com> hath wroth:

>Isn't it amazing the number of "digital generation" people you meet that
>have no concept that you cannot transmit data, directly, over-the-air or
>over long distances, without converting it into the analog world as
>modulation. I've even had college kids in electronic engineering question
>me about why data was "encoded" by some kind of modem for transmission.

The author is apparently somewhere in India. I've discussed their
educational methodology with some of the survivors. It's largely
self-study, which is often interpreted as "get the answers any way you
can". If they can trick someone into doing your homework, all the
better. That's excerbated by the lack of availability in their skools
to get anyone to answer their questions. In addition, it's considered
a capital crime to admit that one doesn't know the answer. It's a
rotten situation and we're seeing the desperate few that are looking
to usenet largely in desperation.

The problem is that if you feed the pigeons, you get more pigeons. If
we continue to do their homework and reports, the only result will be
more students asking for us to do their homework and reports.

I try to give them just enough information to get them kick started,
but not enough to submit to an instructor for an assignment or quiz.

Also, the original author is NOT a dummy. See what he's posted in
other newsgroups:
<http://groups.google.com/groups/profile?hl=en&enc_user=uwJALBsAAABrIaFW2rR1mZdU36XjShcYHL6ZsB4DzFwc97yAjR_7iw>
My guess is that he's having trouble with communications fundamentals,
is in a hurry, or is totally lost. Simply because he's clueless in
communications theory doesn't mean he's also clueless in other topics.

>They're ALL convinced their digital SELLphones are all data, not converted
>into 8K or 11K samples for the phase modulated transmitters...

I've been reading how the various 3G protocols operate and frankly,
I'm lost. Worse, the more I read, the more confused I get.

>Jeff, I noticed your sig on usenet with all your Skype and phone numbers on
>it. Doesn't that create a storm of crank/hate calls from the nutcases on
>here? If not, I'm amazed. I know the spambots will storm email. I had to
>get rid of myhamcall@myisp over it.

Nope. Hardly anyone calls. Probably because I have a reputation for
being mean and nasty.

I have both Skype and GizmoProject set to only accept calls from
people in my address book. They can send me an instant message (chat)
to ask if I'm busy. Most people are considerate. I guess a small
number of Nigerian scammers and people trying to sell me something,
but those usually get a fast disconnect followed by an abuse report.
The only time calls are a problem is when I'm using Skype on my cell
phone (XV6700 running WM5) via Wi-Fi. I have that set for outgoing
calls only.

Incidentally, I've had the same few email addresses for perhaps 15+
years. I've never changed them. I spend my time improving my spam
filtering and mail reading technique. Some spam still gets through,
but nothing intolerable.

As for the nut cases, most will use email instead of a phone call as
they don't want to deal with my mean and nasty bad attitude in real
time. I don't blame them.

What does happen is I get considerable email asking for personalized
help. I try to answer those when possible, but usually I reply that
I'm busy and don't particularly want to deal with their problems. If
they post their question in a newsgroup, various people will answer,
and everyone learns. If they just ask me to solve their problem, I
consider that billable consulting. A few have actually paid for my
advice which helps support my decadent and lavish lifestyle.



--
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

[danny burstein]

In <ncrln3ls9hse9mt4bemu3ie7tn9i4b6hh0@4ax.com> Jeff Liebermann <jeffl@cruzio.com> writes:

>Nope. Hardly anyone calls. Probably because I have a reputation for
>being mean and nasty.

You are Carl J. Lydick and I claim my two-fifty.

--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

[Larry]

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:ncrln3ls9hse9mt4bemu3ie7tn9i4b6hh0@4ax.com:

> As for the nut cases, most will use email instead of a phone call as
> they don't want to deal with my mean and nasty bad attitude in real
> time. I don't blame them.
>
>

Hee hee....You'd make a great 75 meter guy. Mean and nasty is the only way
to get bandwidth!...(c;

I was gonna call on Skype to say hello, but now I'm afraid.

Larry
--
Next time some broker tells you what a great investment he's selling,
ask him about Rhodium, a shiny metal used in Catalytic Converters.
Jan 1st 2004 2005 2006 2007 2008
Rhodium $452 $1341 $3006 $5339 $6775 PER OUNCE!
How much longer can we pay for new cars at this rate?
Feb '97 it was $182/oz

[DTC]

miso@sushi.com wrote:
> It's an analog world!

And an exponential one at that.

For most people, if it sounds TWICE as loud, its TEN times
greater sound pressure level.

[Larry]

DTC <me@nothingtoseehere.zzx> wrote in news:kqPej.33406$lD6.14340
@newssvr27.news.prodigy.net:

> miso@sushi.com wrote:
>> It's an analog world!
>
> And an exponential one at that.
>
> For most people, if it sounds TWICE as loud, its TEN times
> greater sound pressure level.
>

Wouldn't that be logarithmic?....(c;

Larry
--
Next time some broker tells you what a great investment he's selling,
ask him about Rhodium, a shiny metal used in Catalytic Converters.
Jan 1st 2004 2005 2006 2007 2008
Rhodium $452 $1341 $3006 $5339 $6775 PER OUNCE!
How much longer can we pay for new cars at this rate?
Feb '97 it was $182/oz

[Dennis Ferguson]

On 2008-01-02, Larry <noone@home.com> wrote:
> DTC <me@nothingtoseehere.zzx> wrote in news:kqPej.33406$lD6.14340
> @newssvr27.news.prodigy.net:
>
>> miso@sushi.com wrote:
>>> It's an analog world!
>>
>> And an exponential one at that.
>>
>> For most people, if it sounds TWICE as loud, its TEN times
>> greater sound pressure level.
>>
>
> Wouldn't that be logarithmic?....(c;

That would be the same thing. If the perceived loudness is logarithmic
with the sound pressure level, then the sound pressure level is exponential
with perceived loudness.

Dennis Ferguson

[DTC]

Larry wrote:
> DTC <me@nothingtoseehere.zzx> wrote in news:kqPej.33406$lD6.14340
>> For most people, if it sounds TWICE as loud, its TEN times
>> greater sound pressure level.
>>
>
> Wouldn't that be logarithmic?....(c;

Sounds like a (ahem)... *natural* answer to me.