Sega Channel

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Fast Facts on the Sega Channel

Made By: Sega, Scientific Atlanta, General Instrument
Made For: Mega Drive
Size of Program ROM: 256KB

The Sega Channel was a service offered by Sega between December 1994 to mid 1998. It the user to download various games, which changed on a monthly basis.

Technical information

The Sega Channel signal originated in Denver, CO. It was carried over the Galaxy 7 satellite, located 91.0 degrees W longitude using transponder 1 with horizontal polarisation. The uplink signal was at a carrier frequency of 1.435 GHz and occupied 8 MHz bandwidth using QPSK modulation. The downlink signal was at a frequency of 1.1 GHz and occupied 6 MHz bandwidth using QPSK.

Subscriber Loop

  • occupied two 3 MHz non-contiguous channels
  • data rate was 6 Mbit/s
  • tunable to 68 different operating frequencies between 51 and 118 MHz
  • Bit error ratio was <10E-06
  • used Quadrature Partial Response (QPR) modulation

QPR is a modulation scheme that uses a controlled inter-symbol interference. The receiver is capable of logically decoding the signal. QPR provides 20% better bandwidth performance than QPSK with only a minor increase in signal power.

This Sega Channel adapter allowed the customer to download the game selected in less than 1 minute. The adapter contained 4 Megabytes of DRAM, which held games of up to 32 megabits (or 4 megabytes) in size. Once the game was downloaded, it worked exactly as if it were a cartridge, but all saved data and the game itself was lost when the unit was turned off. Sega also had ratings for each game and supplied the parents with a password (4 digit pin number) if so desired.