Astudio transmitter link (STL) sends aradio station's ortelevision station'saudio andvideo from thebroadcaststudio or origination facility to aradio transmitter,television transmitter oruplink facility in another location.[1] This is accomplished through the use of terrestrialmicrowave links or by using fiber optic or other telecommunication connections to the transmitter site.
This is often necessary because the best locations for anantenna are on top of a mountain, where a much shorterradio tower is required, but where locating a studio may be impractical. Even in flat regions, the center of the station's allowed coverage area may not be near the studio location or may lie within a populated area where a transmitter would befrowned upon by the community, so the antenna must be placed at a distance from the studio.
Depending on the locations that must be connected, a station may choose either apoint to point (PTP) link on another specialradio frequency, or a newer all-digital wired link via a dedicateddata transmission circuit. Radio links can also be digital, or the olderanalog type, or ahybrid of the two. Even on older all-analog systems, multiple audio and data channels can be sent usingsubcarriers.
Stations that employ an STL usually also have atransmitter/studio link (TSL) to returntelemetry information. Both the STL and TSL are consideredbroadcast auxiliary services (BAS).
Thetransmitter/studio link (orTSL) of aradio station ortelevision station is areturn link which sendstelemetry data from the remotely locatedradio transmitter ortelevision transmitter back to the studio for monitoring purposes. The TSL may return the same way as the STL, or it can be embedded in the station's regularbroadcast signal as a subcarrier (for analog stations) or a separatedata channel (for digital stations).
Analog or digital data such as transmitterpower, temperature,VSWR, voltage, modulation level, and other status information are returned so thatbroadcast engineering staff can correct any problems as soon as possible. These data may be attended to by anautomated transmission system.