Re: Question about analog cell phones

"Radium" <glucegen1@gmail.com> wrote in message news:1180049314.005680.205030@x18g2000prd.googlegroups.com...
> Hi:
>
> Why do analog cell phones use FM? Why not AM?

Because hard-limiting just prior to the discriminator in an FM receiver
provides a signal-capture effect, in which the strongest of several
competing signals will be received almost free of interference.
Unless the undesired signals are nearly the same strength as the
desired one, the undesired signals are greatly suppressed.

>
> Microwave-frequencies can be done in AM just as well as FM? Why not
> use AM?

Yes, the frequency is irrelevant. FM was chosen for other reasons.

>
> In order to avoid "clipping" and interference with nearby stations,
> the modulator signal should be attenuated prior to D-A conversion and
> transmission. At the receiving end, the carrier signal should be
> amplified prior to demodulation and A-D conversion.

A/D and D/A conversions are techniques used in digital systems, not analog.
However, I did not follow the logic of your statement.
It somewhat resembled the argument for audio-spectrum pre-emphasis
commonly used in recording and broadcasting, but not quite.
That part about amplifying the carrier signal prior to demodulation
made me blink, to say the least.

>
> Radium
>

On May 24, 5:15 pm, "John R. Copeland" <jcope...@columbus.rr.aol.com>
wrote:
> "Radium" <gluceg...@gmail.com> wrote in messagenews:1180049314.005680.205030@x18g2000prd.googlegroups.com...
> > Hi:
>
> > Why do analog cell phones use FM? Why not AM?

> Because hard-limiting just prior to the discriminator in an FM receiver
> provides a signal-capture effect, in which the strongest of several
> competing signals will be received almost free of interference.
> Unless the undesired signals are nearly the same strength as the
> desired one, the undesired signals are greatly suppressed.

Okay.

> > Microwave-frequencies can be done in AM just as well as FM? Why not
> > use AM?
>
> Yes, the frequency is irrelevant. FM was chosen for other reasons.

All right.

>
> > In order to avoid "clipping" and interference with nearby stations,
> > the modulator signal should be attenuated prior to D-A conversion and
> > transmission. At the receiving end, the carrier signal should be
> > amplified prior to demodulation and A-D conversion.

> A/D and D/A conversions are techniques used in digital systems, not analog.
> However, I did not follow the logic of your statement.

Sorry. Please ignore the A/D-D/A part. I accidentaly included it.

> It somewhat resembled the argument for audio-spectrum pre-emphasis
> commonly used in recording and broadcasting, but not quite.

Meaning?

> That part about amplifying the carrier signal prior to demodulation
> made me blink, to say the least.

Why? The idea of amplifying the carrier signal prior to demodulation
is to increase the loudness of the psychedelic heterodynes.

"Radium" <glucegen1@gmail.com> wrote in message news:1180052930.035517.86580@a26g2000pre.googlegroups.com...
> On May 24, 5:15 pm, "John R. Copeland" <jcope...@columbus.rr.aol.com>
> wrote:
>
>> That part about amplifying the carrier signal prior to demodulation
>> made me blink, to say the least.
>
> Why? The idea of amplifying the carrier signal prior to demodulation
> is to increase the loudness of the psychedelic heterodynes.
>

OK, now I realize I've been trolled. Sorry to waste the bandwidth. :-(

"John R. Copeland" wrote:

> OK, now I realize I've been trolled. Sorry to waste the bandwidth. :-(

It's all Radium ever does.

Graham

On May 24, 8:28 pm, Radium <gluceg...@gmail.com> wrote:

> Why? The idea of amplifying the carrier signal prior to demodulation
> is to increase the loudness of the psychedelic heterodynes.

You're an idiot.