Specifications

STUDIO

TRANSMITTER

2 km of multi-mode

dual optical fiber

BROADCAST FACILITY UPGRADE

An FM radio station has a studio facility located next to a hill; to gain antenna height, the station takes advantage

of the hilltop’s extra 300 meters in elevation for its transmitter location. But the distance between the studio

and transmitter sites is slightly over a mile, making a studio-transmitter link (STL) necessary.

Currently, the studio’s stereo air signal goes into an Optimod and a peak limiter, then into the stereo generator,

where the composite audio is sent up to the transmitter site over an aging 950 MHz STL. Piggybacked onto

the composite audio is a subcarrier carrying the audio-frequency analog control signals from the

transmitter remote control. The FM carrier’s 67 kHz SCA subcarrier carries encoded

telemetering signals for logging of transmitter operation. The station’s satellite

downlink is located at the studio, but if it were atop the hill at the

transmitter, the reception would improve and addi-

tional satellites carrying new programming

would be “visible” to the dish.

The design goals

The station management and chief engineer wish to accomplish several goals in this upgrade:

1. Replace the 950 MHz STL.

2. Relocate the station’s satellite dish and receiver to the transmitter site to reduce shadowing by the

hill.

3. Free up the station’s 67 kHz SCA subcarrier, currently used for transmitter telemetering, for other

service uses with revenue-generating potential.

4. Improve overall performance and audio quality.

The RAVE solution

The solution they chose uses a RAVE network with a fiber optic link between the studio and the transmitter

building. The network will use a RAVE 188 in each building, providing line-level analog inputs and outputs, eight

of each. At the studio, a QSC FE 3/1 hub, with three 100baseTX (UTP) ports and one 100baseFX (fiber) port, will

convert the network media to fiber for the long hop to the transmitter building. Its extra ports will allow for the

station to expand its internal routing system using additional RAVE units. The communication on the network

will be bi-directional—not only will it carry the left and right audio channels, SCA audio, and the encoded-audio

control signals for the transmitter and satellite receiver from the studio building to the transmitter building, but

it will also carry stereo audio from the satellite receiver and the encoded-audio telemetering signal in the opposite

direction. Additionally, audio channel overcapacity allows the chief engineer to make use of two channels for

monitoring the audio going into the stereo generator for comparison with the off-air audio signal from the FM

modulation monitor.