By Gerald Bahr, Jeff Blowers, Ed Dice, and Dan Doorn, Cox Cable Communications, Inc.
Orland Park, Illinois was the first 400 MHz system to be designed, built and operated with a full compliment of 51 phase-locked, harmonically related coherent carrier television channels. When completed, the system will have a total of 100 miles of CATV plant, with a maximum cascade of 18 main line amplifiers, one bridger amplifier and two line extenders.
The main line was designed for a spacing of 22 dB at 400 MHz using 3/4" cable for trunk and 1/2" cable for feeder. This design resulted in a feeder-to- trunk ratio of 3:1 with 5.5 actives per mile. The plant design was maximized to withstand the temperature extremes the system will experience and because of the then many unanswered questions concerning the performance of a 400 MHz system, every Main line amplifier position was designed for AGC and ASC operation.
After completing the design, we found the cost for electronics increased approximately 34%, due primarily to the higher usage rate per mile. The cable increased approximately 20% because of the feeder-to-trunk ratio change from 4:1 at 300 MHz to 3:1 for 400 MHz design. All other costs have remained virtually the same, when inflation is accounted for, resulting in a net increase of 13%.