WSCA Station Handbook and Training Manual - Prometheus Radio ...

frequency. This transfer is called modulation. US radio signals use two methods of modulation:
Amplitude Modulation (AM) and Frequency Modulation (FM). WSCA is an FM station.
Using FM, the low frequency audio signal is combined with a higher frequency signal called a “carrier”.
The signal of the carrier is the number you turn to on the dial. In other words, the carrier for Portsmouth
Community Radio is 106.1 Mhz. At the higher frequency, the audio is then able to be broadcast.
B. The WSCA Signal Chain – Where does it go and how does it get there?
The signal chain is the path that our audio travels from the CD players, microphones, etc. (also known as
source devices) located in our studio to the broadcast antenna located at the Portsmouth Music Hall.
See the diagram on the following page for further detail.
Sources
The sources in the studio are the devices that produce audio – either from prerecorded
material or microphones.
Mixer
The sources are connected to the mixer in order to combine them. This is easier than having
a switch to select between them (as you would on a home stereo), and lets us talk over music,
fade between songs, etc.
Studio Head‐End Rack
The equipment shown in the rack on the signal chain diagram is not accessible to the DJs.
This equipment is used to condition the signal for transmission over dedicated telephone
cables to the Music Hall.
Transmitter
The transmitter converts the low level audio signal that originates at the studio to a high
power radio signal. This includes modulation (discussed below) and amplification. The
output of the transmitter is applied to the broadcast antenna.
C. Signal Chain Interruptions ‐
If this signal chain is broken at any point, the audio originating at the studio won’t reach the antenna and
thus won’t be broadcast. Fortunately, all of the devices in the signal chain requiring electrical power are
supported by uninterruptible power supplies that will continue to provide power to the equipment
during short power outages. So, even if the lights go off, we can still broadcast for a period of time.
However, if you become aware that no signal is being broadcast, notify the engineering department
immediately. The phone number for Erik Pearce, co‐chair of engineering is on a contact list posted above
the studio mixing board.
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