mobile phones

Tony Verhulst wrote in
:

Tuno wrote:
snip Is this a technical fact or just a wishfull speculation? /
snip

It is a technical fact.

Both user equipment (your handheld mobile) and radio base stations
(what they talk to) have signal thresholds for "quality of service"
that must be met for normal calls (what you're paying for) to go
through. These thresholds are MUCH lower for text and emergency calls
for obvious reasons: text messages have no real-time requirements (and
much lower bandwidth requirements), and emergency calls are, well,
emergency calls; who cares about quality of service if it's an
emergency.

This is quite similar to the ham radio operator voice vs morse code
situation. While the signal strengths of both types of signals from a
single transmitter will be identical, the *usable* signal strength for
code is much less. This is because if a signal is weak or if there is a
lot of background noise, it is is much easier to detect dots and dashes
than voice.

In addition,
- all other things being equal, at low SNR AM gives a
better quality than FM
- morse code can operate with a narrower RF bandwidth,
thus reducing noise and increasing SNR