Drake SCT4860 8PSK Sat-1024QAM Cable Transcoder - Manual (Page 12)

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OUTPUT LEVEL
the SCt4860 provides a +40 dBmV qAm output level that is desirable when transcoders are combined with
analog modulators that have +45 dBmV output level. the SCt4860 output level can be turned down as much as
15 dB if a lower level is desired. each SCt4860’s Rf output level can be read out on the PS151 power supply
LCD when that unit is selected, or via the RS232 remote connection.
Because some operators may not have test equipment designed to measure qAm power levels, and analog
meters may be grossly inaccurate if a qAm signal is read, the SCt4860 has a CW output mode that can be
useful for measuring/adjusting the output level of the transcoder with any meter that measures CW carrier power.
A special qAm instrument is not required. No input signal is required for this measurement. the CW carrier power
is equal to the qAm power level that will result when the unit is returned to a normal qAm modulation mode.
IMPORTANT NOTE: When the SCt4860 is placed in the continuous wave (CW) mode, the output carrier
frequency will be at the center of the output channel. it will not be located at the NtSC video carrier frequency.
Adjust test equipment accordingly to obtain an accurate result.
the PC control software allows all transcoders to be easily switched to the CW mode at one time for set up
purposes. After any level tweaks are made, they can all be switched back to normal mode at one time. it is also
possible to individually select a single transcoder to be switched to the CW mode, if desired. in a typical leveling
process, the output of the headend is monitored after the final combiner and all analog channel levels are set
to the desired level. then, with the SCt4860s all set for CW output, the SCt4860 CW carrier levels can be all
tweaked to a desired level (usually 6 to 10 dB) below the analog video carrier levels. When switched back to
normal mode, the SCt4860s will all be outputting qAm channel powers equal to the CW powers set up.
RAIN FADE LOGIC
When the rain fade feature is enabled, the transcoder will mute its Rf output whenever the input S/N drops below
a usual level. this logic is always enabled in the DiSHScan mode.
STANDBY MODE
the SCt4860 has a standby output mode which turns off the Rf output. this can be used when it is desirable
to keep a backup unit on line. the standby mode can be selected via the outPut menu.
POWER SUPPLY
the SCt4860 requires multiple power supply voltages that are all obtained from the Drake model PS151 power
supply module. the PS151 mounts in the Rmt150 rack tray along with one to ten SCt4860 (or other similar
Drake models) transcoders. the PS151 buffers and distributes the RS232 remote control data from its DB9,
RS232 iNPut connector to up to ten transcoders and to the DB9, RS232 outPut connector. multiple PS151s
can be ‘daisy chained’ via the DB9 iNPut and outPut connectors to allow control of up to 70 transcoder
modules with a single connection to a PC.
the PS151 operates over a wide range of AC input voltages from 90 VAC to 264 VAC. the uSA version has
an attached 3 wire line cord. Power consumption from the AC line will be around 150 W maximum with ten
transcoders installed. in many cases, the power will below this level.
Additional Features