Why 2 Mbit/s?

 

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because a data rate of 2 Mbit/s is much higher than the 1200 bit/s and the 9600 bit/s we use in packet systems, and even the 56 kbit/s, ceiling of the V90 telephone modems. This makes it possible to consider interesting applications: transmissions of animated compressed images in MPEG, transmission of vocal signals and data files. With 2 Mbit/s it is possible to transmit animated images with a very good quality.

- because to handle of 2 Mbit/s is not very complicated. The current integrated circuits are appropriate, technology is banal.

- because a channel of television presents a bandwidth of 6 or 7 MHz and that such a bandwidth easily makes it possible to transmit several Mbit/s. With simple personal achievements and while taking some precautions we will be able to transport 2 Mbit/s in an ATV channel.

- because one can regenerate the digital signal in the repeaters, and thus significantly to limit the cumulative effect of the noise.

- because in the world of European telecommunications*, the 2 Mbit/s trunks are very widespread, and this since several dozens of years. It constitutes the basis building block of the networks. So there exists for a long time for 2 Mbit/s normalization and a whole environment: interfaces, specific integrated circuits, measuring equipments (which one will end to discover one day or the other in a trash or at low prices in a scrap merchant).

 

* NB: The standardized data rate is of 2.048 Mbit/s. On the North-American continent telcos use for the same purpose a data rate of 1.544 Mbit/s

 

Long live for the ham construction and experimentation !

 

B5+ et 73 de Jean-François Fourcadier, F4DAY

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© 2000-2004  J.F. Fourcadier F4DAY