DRAKE 1002365 Manuals

INSTALLATION IN THE SCT860 Looking at the SCT860 from the front panel, observe the right side of the unit. Remove the three top screws as shown, three side screws, and three bottom screws holding the right side of the case. Remove the right side and then lay the transcoder on a flat surface laying on its left side. Locate the 36 pin interface connector and remove the 11 jumpers that are in place. Keep these jumpers for future use in case the 100-2365 board is ever removed. Remove the original screw at location A. Screw the standoff spacer, that is included with the option board, into the hole at location A. Carefully remove the 100-2369 board from its static protection package. Position the board as indicated and plug it into the 36 pin connector. Reinstall the screw to fasten the Option Board to the spacer. Replace the right side cover and screws. FIRMWARE UPDATE REQUIRED Install the "Fixed" version of the SCT860 operating firmware. This is provided on the included floppy disk. Download via the RS-232 interface on the PS100. This firmware is also available on the CD- ROM included with the PS100. OPERATION Follow the instructions in the SCT860 instruction manual. Now that the 100-2365 board is installed, the FIXED clock option may be selected and the output BD RATE (baud rate which is the symbol rate) may be set. The original AUTO clock mode is still selectable, if desired. Installation / Operation 2 INTRODUCTION The 100-2365 board is used to add a fixed, programmable, clock option to the SCT860 transcoder. Why is this needed? When the standard SCT860 demodulates the satellite signal and recovers the MPEG2 transport stream, the data rate of this stream has been determined at the satellite uplink. This data rate, the FEC mode, required guard bands, etc. have all been carefully selected to optimize the use of a 27 MHz wide satellite transponder and a 6 MHz wide 64 QAM CATV channel. The resulting design provides a transport stream bit rate of around 27 Mb/s. This bit rate results in a 64 QAM symbol or baud rate of 5.057 MS/s. This rate completely fills the 6 MHz channel. The standard SCT860 does not modify the transport stream and thus performs the desired translation from the satellite channel to the terrestrial QAM channel producing the output rate as described above. Drake labels this mode the ‘Auto Clock’ mode as the output rate is automatically determined by the received input signal data rate. Sometimes there are reasons for the satellite uplink to use a different data rate than that which produces the 5.057 MS/sec, 64 QAM data rate. For example, if 36 MHz wide transponders are used, not all of the satellite bandwidth is being utilized with only a 27 Mbps bit rate - a higher satellite rate is possible to make maximum use of the satellite bandwidth. If the satellite rate is increased to make optimum use of the wider satellite transponder, after transcoding, the resulting output signal would exceed the maximum 6 MHz CATV channel bandwidth. If priority is given to utilizing all of the satellite bandwidth then a higher order of CATV modulation, such as 256 QAM, must be used to accommodate the additional data rate on the QAM output side OR some of the excess data must either be deleted or split so as to deliver it in two CATV channels. 3 TOP SCREWS 1 TM Model 100-2365 Fixed Clock/Null Packet Stuffing Option Board (SCT860) When it is not desirable to go to 256 QAM modulation, one possibility, if some of the information is not needed at any one receiver, is to encode the uplinked signal such that all bits from any one program source are coded to only bits of the Q channel or the I channel. Then it is possible to demodulate the satellite signal at the transcoder and use only the I or Q side (SCT860 Split-I or Split-Q mode). The resulting data rate is then below the available maximum capacity with 64 QAM modulation. The standard SCT860, in auto clock mode, would output the resulting reduced symbol rate signal at a symbol rate below the 5.057 MS/s maximum rate but, unfortunately, many set top boxes will only sync to the 5.057 maximum rate. This is where the 100-2365 board is used. This option allows the user to select a ‘Fixed Clock’ mode. The desired output symbol rate (such as 5.057 MS/s) can be programmed. The 100-2365 option will then add MPEG2 null packets to the transport stream (sometimes called ‘null packet stuffing’) as needed to increase the symbol rate to the one programmed. The set top box will just ignore the extra null packets. By using two SCT860 transcoders with the 100-2365 option to receive the same satellite transcoder (using split mode) and setting one for the ‘Split-I’ mode and one for the ‘Split-Q’ mode, the entire satellite payload can be split between two different CATV 64 QAM channels thus transcoding all of the satellite program services. It is necessary for the signal to be uplinked in the split mode in order for this process to work. REMOVE 11 JUMPERS FROM THE 36 PIN CONNECTOR LOCATION A PLUG INTERFACE HEADER INTO 36 PIN CONNECTOR TIGHTEN SCREW INTO SPACER