User manual

Appendix F: Redundant Backup F-11
Moseley SL9003Q 602-12016 Revision G
F.5.3 Digital STL with Analog STL Backup using a TPT-2
System Considerations
Incompatible Modulation Formats
The PCL series analog STL’s (or any analog STL) may be used as a backup for the Starlink
with awareness of the how operational differences between the two systems effect backup
operation. Specifically the two systems have incompatible rf modulation formats. The analog
STL links (i.e., PCL series) use Frequency Modulation (FM) vs. Quadrature Amplitude
Modulation (QAM) for the Starlink digital STL links. An FM transmitter will not work with a QAM
receiver and visa versa.
What this means is the backup does not operate in the traditional redundant sense. Only one
link can be active at a time, the QAM STL receiver is valid when QAM STL transmitter is
selected, and analog STL receiver when the analog STL transmitter is selected.
For instance the transfer panel will switch to a back-up transmitter when a failure mode is
detected in the main transmitter. If the Starlink transmitter is selected as main and fails then the
Starlink receiver will automatically switch over to the analog backup receiver when it fails to
decode the analog transmission from the PCL6000 or 606.
But if a receiver fails (at the receiver end), the back-up receiver will not be able to take over until
the transmitters are forced to switch to the compatible unit. In this case the transmitter
switchover can be accomplished through the use of a return telemetry signal via remote control,
which detects the failed receiver and sends back a control line to transfer at the studio site.
Composite vs. Discrete Audio
The other issue is most typical PCL6000/606 links are set for composite FM transmission. The
Starlink SL9003Q is a discrete audio link and does not support this type of composite baseband.
The Starlink Digital Composite STL must be used if intended to operate as a backup with a
composite analog system.
Alternatively a PCL6000/606 composite STL system may be made compatible with a Starlink
SL9003Q Discrete Audio STL if it is first converted to a discrete digital system through the use
of a DSP6000. This will provide the discrete audio (left/right or digital AES) necessary for
switchover.
Using a TPT-2 Transfer Panel
The TPT-2 has the appropriate logic to work properly with the PCL series STL transmitters. We
therefore recommend using a TPT-2 transfer panel when using the PCL series analog STLs
rather than the TP64 transfer panel for the hybrid analog/digital backups that will be discussed.