Analog VS Digital Question

I understand that analog uses more power than digital. Is this because
the transmitter is always on, where as with digital the transmitter is
only on part of the time? Like on for 1, off for 0? Something like
that? TDMA phones seem to have a problem with making speakers buzz as
the transmitter goes on and off. But why doesn't any phone that's
digital do this? Like CDMA, the transmitter is turning on and off
rapidly as it's sending out it's info, why doesnt that make the
speakers make a funny buzzing noise?

Thanks!

Mike


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ChaosThyre81

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› See More: Analog VS Digital Question

On Wed, 16 Mar 2005 05:36:35 +0000, ChaosThyre81
<[email protected]> wrote:

>I understand that analog uses more power than digital. Is this because
>the transmitter is always on, where as with digital the transmitter is
>only on part of the time?

Output power spec is higher. Digital designers thought they could cut
corners and get moredata into less bandwidth and power. Listen to one of
each, then you'll see that compromises were made.

<snip>
> TDMA phones seem to have a problem with making speakers buzz as
>the transmitter goes on and off. But why doesn't any phone that's
>digital do this? Like CDMA, the transmitter is turning on and off
>rapidly as it's sending out it's info, why doesnt that make the
>speakers make a funny buzzing noise?

CDMA uses an entirely different modulation system than GSM & TDMA (which
are very similar) and its emissions just aren't as strong, so it interferes
much less.


--
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John Bartley, K7AAY, PDX OR USA, Opinions mine.

>>I understand that analog uses more power than digital. Is this because
>>the transmitter is always on, where as with digital the transmitter is
>>only on part of the time?
>
> Output power spec is higher. Digital designers thought they could cut
> corners and get moredata into less bandwidth and power. Listen to one of
> each, then you'll see that compromises were made.
>
> <snip>
>
>>TDMA phones seem to have a problem with making speakers buzz as
>>the transmitter goes on and off. But why doesn't any phone that's
>>digital do this? Like CDMA, the transmitter is turning on and off
>>rapidly as it's sending out it's info, why doesnt that make the
>>speakers make a funny buzzing noise?
>
> CDMA uses an entirely different modulation system than GSM & TDMA (which
> are very similar) and its emissions just aren't as strong, so it interferes
> much less.

I'm not technical enough to know, but I have heard that CDMA does have
interference, but it is more random and not patterned as much as TDMA
based devices (TDMA/GSM/iDEN). It sounds like it could be possible, but
I truly have no idea.

Joseph wrote:
> On Wed, 16 Mar 2005 05:36:35 +0000, ChaosThyre81
> <[email protected]> wrote:
>
>>TDMA phones seem to have a problem with making speakers buzz as
>>the transmitter goes on and off. But why doesn't any phone that's
>>digital do this?
>
> GSM also causes RF interference when transmitting especially when a
> GSM handset is ringing.

GSM, U.S. "TDMA" (IS-136), and iDEN (Nextel) use Time Division Multiple
Access air protocols. This means that they they get a time slice during
which they transmit and receive. All of the power has to go into this
narrow pulse. This pulsing several hundred times per second is what
causes the interference with speakers and other equipment.

When a CDMA (Code Division Multiple Access) phone is in a call or doing
other occasional chit-chat with the system, it is transmitting
continuously at a very low power level with the signal spread across a
wide band (1.25MHz for the current CDMA systems). They are very unlikely
to cause interference; in fact, without knowing the specific coding
parameters for that particular call, it is very difficult to distinguish
the signal of a CDMA phone from background noise even with sophisticated
receivers, let alone for it cause interference with random equipment.