I have examined the signals of two cable companies in West Virginia who employ scrambling techniques and find that no actual scrambling is being done. That is, the signals are not "mixed up" in any way. All that has been done is the horizontal sync and blanking pulses have been suppressed about 6 db below the peak video level. Except for that modification all the signal components are intact and in proper sequence. The scrambling occurs inside the TV receiver because of its inability to locate and lock on to the horizontal sync pulses.
If you are interested in this kind of experimenting, an excellent series of articles began in the June 1986 issue of "Radio Electronics" and is continuing as of this date (August 1986). It may also be of value to know where the signals you want to work on are located in terms of frequency. If you have ever wondered where those mid band and super band cable channels are located, the following table will be enlightening.
Table of CATV Channels VS. Frequency in MHz --------------------------------------------- ! Channel ! ! Video ! Audio ! ! Number ! Bandwidth ! Carrier ! Carrier ! !---------------------------------------------! ! T7 ! 5.75- 11.75! 7.0 ! 11.5 ! ! T8 ! 11.75- 17.75! 13.0 ! 17.5 ! ! T9 ! 17.75- 23.75! 19.0 ! 23.5 ! ! T10 ! 23.75- 29.75! 25.0 ! 29.5 ! !---------------------------------------------! ! TV-IF ! 40.0 - 46.0 ! 41.25 ! 45.75 ! !---------------------------------------------! ! 2 ! 54.0 - 60.0 ! 55.25 ! 59.75 ! ! 3 ! 60.0 - 66.0 ! 61.25 ! 65.75 ! ! 4 ! 66.0 - 72.0 ! 67.25 ! 71.75 ! ! 5 ! 76.0 - 82.0 ! 77.25 ! 81.75 ! ! 6 ! 82.0 - 88.0 ! 83.25 ! 87.75 ! !---------------------------------------------! ! FM Radio! 88.0 - 108.0 ! ! ! !---------------------------------------------! ! A-2 ! 108.0 - 114.0 ! 109.25 ! 113.75 ! ! A-1 ! 114.0 - 120.0 ! 115.25 ! 119.75 ! ! A (14) ! 120.0 - 126.0 ! 121.25 ! 125.75 ! ! B (15) ! 126.0 - 132.0 ! 127.25 ! 131.75 ! ! C (16) ! 132.0 - 138.0 ! 133.25 ! 137.75 ! ! D (17) ! 138.0 - 144.0 ! 139.25 ! 143.75 ! ! E ! 144.0 - 150.0 ! 145.25 ! 149.75 ! ! F (19) ! 150.0 - 156.0 ! 151.25 ! 155.75 ! ! G (20) ! 156.0 - 162.0 ! 157.25 ! 161.75 ! ! H (21) ! 162.0 - 168.0 ! 163.25 ! 167.75 ! ! I (22) ! 168.0 - 174.0 ! 169.25 ! 173.75 ! !---------------------------------------------! ! 7 ! 174.0 - 180.0 ! 175.25 ! 179.75 ! ! 8 ! 180.0 - 186.0 ! 181.25 ! 185.75 ! ! 9 ! 186.0 - 192.0 ! 187.25 ! 191.75 ! ! 10 ! 192.0 - 198.0 ! 193.25 ! 197.75 ! ! 11 ! 198.0 - 204.0 ! 199.25 ! 203.75 ! ! 12 ! 204.0 - 210.0 ! 205.25 ! 209.75 ! ! 13 ! 210.0 - 216.0 ! 211.25 ! 215.75 ! !---------------------------------------------! ! J (23) ! 216.0 - 222.0 ! 217.25 ! 221.75 ! ! K ! 222.0 - 228.0 ! 223.25 ! 227.75 ! ! L ! 228.0 - 234.0 ! 229.25 ! 233.75 ! ! M ! 234.0 - 240.0 ! 235.25 ! 239.75 ! ! N ! 240.0 - 246.0 ! 241.25 ! 245.75 ! ! O ! 246.0 - 252.0 ! 247.25 ! 251.75 ! ! P ! 252.0 - 258.0 ! 253.25 ! 257.75 ! ! Q ! 258.0 - 264.0 ! 259.25 ! 263.75 ! ! R ! 264.0 - 270.0 ! 265.25 ! 269.75 ! ! S ! 270.0 - 276.0 ! 271.25 ! 275.75 ! ! T ! 276.0 - 282.0 ! 277.25 ! 281.75 ! ! U ! 282.0 - 288.0 ! 283.25 ! 287.75 ! ! V ! 288.0 - 294.0 ! 289.25 ! 293.75 ! ! W ! 294.0 - 300.0 ! 295.25 ! 299.75 ! !---------------------------------------------! ! AA ! 300.0 - 306.0 ! 301.25 ! 305.75 ! ! BB ! 306.0 - 312.0 ! 307.25 ! 311.75 ! ! CC ! 312.0 - 318.0 ! 313.25 ! 317.75 ! ! DD ! 318.0 - 324.0 ! 319.25 ! 323.75 ! ! EE ! 324.0 - 330.0 ! 325.25 ! 329.75 ! ! FF ! 330.0 - 336.0 ! 331.25 ! 335.75 ! ! GG ! 336.0 - 342.0 ! 337.25 ! 341.75 ! ! HH ! 342.0 - 348.0 ! 343.25 ! 347.75 ! ! II ! 348.0 - 354.0 ! 349.25 ! 353.75 ! ! JJ ! 354.0 - 360.0 ! 355.25 ! 359.75 ! ! KK ! 360.0 - 366.0 ! 361.25 ! 365.75 ! ! LL ! 366.0 - 372.0 ! 367.25 ! 371.75 ! ! MM ! 372.0 - 378.0 ! 373.25 ! 377.75 ! ! NN ! 378.0 - 384.0 ! 379.25 ! 383.75 ! ! OO ! 384.0 - 390.0 ! 385.25 ! 389.75 ! ! PP ! 390.0 - 396.0 ! 391.25 ! 395.75 ! ! QQ ! 396.0 - 402.0 ! 397.25 ! 401.75 ! ! RR ! 402.0 - 408.0 ! 403.25 ! 407.75 ! ! SS ! 408.0 - 414.0 ! 409.25 ! 413.75 ! ! TT ! 414.0 - 420.0 ! 415.25 ! 419.75 ! ! UU ! 420.0 - 426.0 ! 421.25 ! 425.75 ! ! VV ! 426.0 - 432.0 ! 427.25 ! 431.75 ! ! WW ! 432.0 - 438.0 ! 433.25 ! 437.75 ! ! XX ! 438.0 - 444.0 ! 439.25 ! 443.75 ! ! YY ! 444.0 - 450.0 ! 445.25 ! 449.75 ! ! ZZ ! 450.0 - 456.0 ! 451.25 ! 455.75 ! ---------------------------------------------