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Re: communications rates was Re: Differential voltage probes 3
Original poster: "davep by way of Terry Fritz <teslalist-at-qwest-dot-net>" <davep-at-quik-dot-com>
(We are getting a bit away from Tesla, or HV....)
>>>Terry, I predict that just as we now have audio TC transmission we will
>>>have future video TC transmission with this new found wide
>>>bandwidth. It only takes 6-8 Mhz bandwidth for video.
> > Sorry, but transmitting 6 MHz bandwidth on a carrier of a
>>few hundred KHz is forbidden by communications theory.
Shannon referred to _binary_ (on off) keying,
or two tone tone signalling. If multi level,
either analog, or discrete steps be employed,
more BW can be fit in.
>- Communications theory (if you're referring to the Shannon law) only
>provides a limit on the amount of information you can get through a
>channel, and doesn't constrain the bandwidth required for the
>information, other than setting a minimum Signal to Noise ratio.
>- Transmitted bandwidth doesn't necessarily follow the bandwidth of the
>modulating signal. Take FM broadcast band, modulation bandwidth is on the
>order of 20 kHz, and the signal is >100 kHz wide.
Design choice. FM for eg 'police radio' is 15 KHz wide,
for 10 KHz (roughly) audio. The wider channel
spacing in 'broadcast FM' allows for more fidelity.
> Or, AM broadcast, where the modulation is some 5-8 kHz, and the
>transmitted signal is 15 kHz wide (being DSB).
>- Baseband video (like comes out of the VCR) is 6 MHz wide, at a
>carrier frequency of ZERO.
Basebaand video, by deninition HAS NO carrier.
When broadcast (or otherwise on a carrier) it is
a sort of single side band, with a 6 MHz BW....
>One can certainly transmit very high rate digital signals in a fairly
>narrow bandwidth, IF you have enough power. HDTV is some
>20Mbps in a 6 MHz wide channel. 56k modems are doing 56 kbps
>in a 3 kHz channel.
by using multi level encoding. The Shannon
bit/Hz criteria ASSUMES BINARY keying.