View Full Version : Question about analog cell phones
Radium[_4_]
May 25th 07, 12:28 AM
Hi:
Why do analog cell phones use FM? Why not AM?
Microwave-frequencies can be done in AM just as well as FM? Why not
use AM?
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.
Thanks,
Radium
Geoff
May 25th 07, 12:53 AM
Radium wrote:
> Hi:
>
> Why do analog cell phones use FM? Why not AM?
>
> Microwave-frequencies can be done in AM just as well as FM? Why not
> use AM?
Why ? AM is more susceptable to noise and inrterference.
>
> 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.
Yer what ?
geoff
On May 24, 7:28 pm, Radium > wrote:
> Hi:
>
> Why do analog cell phones use FM? Why not AM?
>
Do you even know if they do?
> Microwave-frequencies can be done in AM just as well
> as FM? Why not use AM?
Why not use FM?
Do you know they use FM?
> In order to avoid "clipping" and interference with nearby stations,
> the modulator signal should be attenuated prior to D-A conversion and
> transmission.
Why?
Why would you use D-A conversion at the TRANSMITTER?
> At the receiving end, the carrier signal should be
> amplified prior to demodulation and A-D conversion.
Why would you use A-D conversion at the RECEIVER?
If it's an "analog phone," why is it using A-D and D-A?
Do you know what an "analog cell phone" is?
John R. Copeland
May 25th 07, 01:15 AM
"Radium" > wrote in message oups.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
>
Eeyore
May 25th 07, 01:15 AM
Radium wrote:
> Hi:
Oh right. You're not blocked on this news server !
Bye.
Graham
Radium[_4_]
May 25th 07, 01:24 AM
On May 24, 4:55 pm, wrote:
> On May 24, 7:28 pm, Radium > wrote:
>
> > Hi:
>
> > Why do analog cell phones use FM? Why not AM?
>
> Do you even know if they do?
Yes. I read about it.
>
> > Microwave-frequencies can be done in AM just as well
> > as FM? Why not use AM?
>
> Why not use FM?
FM is limited to line of sight.
> > In order to avoid "clipping" and interference with nearby stations,
> > the modulator signal should be attenuated prior to D-A conversion and
> > transmission.
>
> Why?
>
> Why would you use D-A conversion at the TRANSMITTER?
>
> > At the receiving end, the carrier signal should be
> > amplified prior to demodulation and A-D conversion.
>
> Why would you use A-D conversion at the RECEIVER?
>
> If it's an "analog phone," why is it using A-D and D-A?
>
> Do you know what an "analog cell phone" is?
Sorry. I should've left out the D-A/A-D conversion.
Stupid me.
Radium[_4_]
May 25th 07, 01:26 AM
On May 24, 4:53 pm, "Geoff" > wrote:
> Radium wrote:
> > Hi:
>
> > Why do analog cell phones use FM? Why not AM?
>
> > Microwave-frequencies can be done in AM just as well as FM? Why not
> > use AM?
> Why ? AM is more susceptable to noise and inrterference.
AM interferences are more interesting and entertaining than the boring
hiss you get with bad FM reception.
Radium[_4_]
May 25th 07, 01:28 AM
On May 24, 5:15 pm, "John R. Copeland" >
wrote:
> "Radium" > wrote in ooglegroups.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.
John R. Copeland
May 25th 07, 01:45 AM
"Radium" > wrote in message ups.com...
> On May 24, 5:15 pm, "John R. Copeland" >
> 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. :-(
Eeyore
May 25th 07, 02:05 AM
"John R. Copeland" wrote:
> OK, now I realize I've been trolled. Sorry to waste the bandwidth. :-(
It's all Radium ever does.
Graham
Michael Black
May 25th 07, 02:41 AM
Radium ) writes:
Don't forget that "radium" is a well-known troll, and the fact that
he has cross-posted this to
alt.cellular
alt.cellular-phone-tech
rec.audio.misc
rec.audio.tech
alt.cellular.verizon
should be a giveaway if nothing else is.
He takes some little bit of "knowledge" and then trolls with it.
Note that he knows what kind of mudlation cellphones use, but
claims to not have a clue about why it would be used. You basically
don't get one without some concept of the other.
Michael
Mr.T
May 25th 07, 03:04 AM
"Radium" > wrote in message
ups.com...
> Stupid me.
At last a Radium statement I can agree with :-)
MrT.
On May 24, 8:24 pm, Radium > wrote:
> On May 24, 4:55 pm, wrote:
>
> > On May 24, 7:28 pm, Radium > wrote:
>
> > > Hi:
>
> > > Why do analog cell phones use FM? Why not AM?
>
> > Do you even know if they do?
>
> Yes. I read about it.
Do you even KNOW if they do?
You seem to read about a lot of things and still consistently,
reliably get it wrong.
> > > Microwave-frequencies can be done in AM just as well
> > > as FM? Why not use AM?
>
> > Why not use FM?
>
> FM is limited to line of sight.
Wrong. Utterly, totally, completely wrong.
I sit here listening to WCRB at about 100 MHz,
55 miles away, well beyond line of site distance.
Now, once again, why NOT use FM?
> Stupid me.
Okay, you're now on record for your FIRST correct
statement. How about going for a streak?
On May 24, 8:28 pm, Radium > 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.
Bob's Backfire Burrito
May 25th 07, 02:52 PM
"Radium" > wrote in message
oups.com...
> On May 24, 4:53 pm, "Geoff" > wrote:
>
>> Radium wrote:
Spoken like a true CB'er there Radium....
You are totally CLUELESS!
All you seem to know are buzzwords and have no idea how "radio" works.
Karl Uppiano
May 26th 07, 01:16 AM
"Bob's Backfire Burrito" > wrote in message
t...
>
> "Radium" > wrote in message
> oups.com...
>> On May 24, 4:53 pm, "Geoff" > wrote:
>>
>>> Radium wrote:
>
> Spoken like a true CB'er there Radium....
> You are totally CLUELESS!
> All you seem to know are buzzwords and have no idea how "radio" works.
The similarities between Usenet and CB are staggering.
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