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INTRODUCTION
Studio-Transmitter Link
Transmission from Studio to Transmitter
The peak limiters can be switched to operate either "flat" or on a 50s or 75s pre-
emphasis curve to protect a pre-emphasized path like a typical analog microwave
STL.
When operated in pre-emphasized mode, the peak limiters should only
be used for light protection limiting with a low duty cycle. Otherwise,
you may hear pumping on material with a lot of high frequency energy
like sibilance.
Because the look-ahead peak limiting technology used in the 6300 per-
forms optimally with "flat" transmission channels (like almost all digital
channels), the 6300 cannot provide loudness processing for pre-
emphasized radio channels. Use one of Orban's Optimod-FM processors
for this application. For analog television with FM aural carrier(s), use
Optimod-TV 8382.
The following information is mainly relevant to digital radio and TV broadcasters
who have their transmitters and studios at different locations. Most netcasters will
not find the information in this section relevant because if netcasters need to ship
audio beyond their LAN, they ordinarily ship it from one location to another in the
form of encoded audio through low-capacity Telco-supplied digital links like ISDN or
E-1/T-1.
There are five types of studio-transmitter links (STLs) in common use in broadcast
service: uncompressed digital, digital with lossy compression (like MPEG, Dolby
®
APT-x
), microwave, analog landline (telephone/post line), and audio subcarrier on a
video microwave STL.
At this writing, we believe that the Internet is insufficiently reliable to
serve as a carrier for a real-time STL because of the risk that network in-
terruptions might randomly disturb the audio feed.
STLs are used in two fundamentally different ways. Either they can pass unprocessed
audio for application to OPTIMOD 6300's input or they can pass OPTIMOD 6300's
peak-controlled output. The two applications have fundamentally different per-
formance requirements.
A link that passes unprocessed audio should have very low noise and low non-
linear distortion, but its transient response is not important.
A link that passes processed audio does not need as low a noise floor as a link
passing unprocessed audio. However, its transient response is critical. In DAB ap-
plications, such a link must be uncompressed digital and must use digital inputs
and outputs to achieve best results. We will elaborate below.
ORBAN MODEL 6300
®
, or
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Troubleshooting
