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Old July 16th 07, 12:30 AM posted to sci.electronics.basics,rec.radio.shortwave,rec.radio.amateur.antenna,alt.cellular.cingular,alt.internet.wireless
Jeff Liebermann[_2_] Jeff Liebermann[_2_] is offline
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First recorded activity by RadioBanter: Jun 2007
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Default How I would like to change the cell phone industry [was AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency]

Radium hath wroth:

There will probably need to be 8-10 times more cell sites
built than are currently in use on 800/900 and 1800/1900MHz.


Why?


For a given radio system, higher frequencies don't go as far as lower
frequencies. You can see how it works by just plugging in different
frequencies a "free space loss" calculator such as:
http://www.terabeam.com/support/calculations/free-space-loss.php
For every 6dB of additional path loss, your range is cut in half.
Incidentally, this is not my idea or a conspiracy. Mother nature made
it that way and we have to live with the physics.

I'll make it really simple for you. FM is "hi-fi", while AM is noisy
"no-fi".


FM has too much hiss.


FM has a limiter that eliminates all AM noise components. That's
exactly the way the soon to be obsolete analog cell phones operate. If
you're hearing hiss, then there's something broken in your FM stereo.

FM signals are lost very easily.


I have a lost and found for missing signals. It's called a spectrum
analyzer. If the signal wanders, I can usually find it. Not a
problem.

AM tends to
retain reception of a signals even when this signal is extremely weak.


Not really. If you really want weak signal reception, I suggest you
look into SSB (scientific set back) modulation. Half the bandwidth
gives you twice the sensitivity.

In FM, once you go below a certain wattage, you completely lose the
signal, and the annoying hiss begins. With AM it is much easier to
receive the low-power signal.


Nope. All FM receivers have a squelch to mute the receiver when
there's not enough signal to make it worth listening. The squelch is
much more efficient with FM than an AGC operated squelch for AM.
Anyway, if someone calls with me on my cell phone with a crummy
signal, I don't want to talk to them and I usually ask them to call me
back when in a better area.

The problem with AM audio is that the ultimate signal to noise ratio
isn't very good. AM is noisy at any signal strength. The noise never
really goes away. On the other foot, FM is noisy with very weak
signals, but becomes very quiet once the limiter starts to work.
That's why FM is preferred for music and why analog AM broadcasting
sounds marginal at any signal level.

AM maybe more vulnerable to electronic disturbances but so what? The
magnetic RF interferences that are heard on the AM radio are
entertaining compared to the deafening hiss on the FM radio.


If your FM radio has a deafening hiss, you're probably not tuned to
any station. Try listening to a station instead of between stations.
If it has an AFC, turn it on. There may also be some kind of
malfunction in your hi-fi as you should not be hearing any hiss when
tuned to a station.

For decent quality, you
gotta have FM.


Nope. For decent quality sound you need audio that is uncompressed PCM
[similar to CDs and WAVE files] with a sample rate of at least 44.1
KHz and a bit-resolution of at least 16-bit. Or the analog equivalent.


I thought you didn't like digital? You only gave me a choice of AM or
FM. Now, you want digital. Well, digital is what today's cell phones
use mostly to maximize spectrum efficiency. With compression and
proper coding, you can pickup quite a bit of efficiency, at the
expense of sounding like you're gargling ball bearings. Not too bad a
tradeoff for voice. Really awful for music. Fortunately, none of the
broadcasters or cellular carriers use raw CD data, mostly because it's
not compressed.

So, are you ready to go public with your idea? When's the IPO?

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558