Issue link: https://digital.copcomm.com/i/1543070
C I N E M A A U D I O S O C I E T Y. O R G 55 the property, would become our Control Center (CC). Our main goal was to capture all the actors' dialogues no matter where the action took them. Fiber optics would help us straddle those distances and avoid multiple runs of heavy coaxial cable. Our solution was setting up three nodes in a straight line. The middle node being my sound cart in the CC, connected to the other two ("North" and "South") at each end of the property, via fiber optic cable. The Nitty-Gritty The specific term for these systems is RFoF (RF over Fiber). The basic RFoF configuration has three elements: a transmitter module, a receiver module, and a length of fiber optic cable. The TX (transmitter) takes the RF signals coming from the antennas, converts them to fiber optic data (light pulses), which travels through the fiber cable toward the RX (receiver), and turns it back into RF signals to be decoded by the receivers at the sound cart. The wireless systems we use in production sound (made by companies such as Lectrosonics, Wisycom, and Sound Devices) are designed to use antennas in pairs. Most manufacturers have an "Antenna Diversity" function which constantly compares the signals coming through both antennas and switches from one to the other depending on which has the stronger signal. The antennas are usually installed three to four feet apart, equidistant from the scene being filmed. Because of this, at every zone, we had to deploy two RFoF systems, one for each paired antenna. Building the System Our main cart, in the CC, would accommodate two pairs of RX modules labeled "North" and "South." Two 500' rolls of fiber cable were spooled out from the CC, one toward the North node and the other going South. The two remote nodes were housed in Pelican-type cases. Each case contained two RFoF TX's, a Dante media converter (Dante is a powerful audio-over-Ethernet protocol that allows various devices to be patched together via Ethernet cables), and an AC power supply. We included the Dante link because our fiber cables had two available strands. We thought a Dante connection at the remote nodes could be useful, and we were right. Dan Kelly CAS (my fellow mixer on this project) built a compact sound cart with a redundant multi-track recorder, which we could deploy whenever we filmed in an area with poor reception. Patching Dan's recorder into our main Dante network took a minute or so but allowed us to have a redundant, clean recording of all the tracks in play. This also provided a reliable wireless feed for the camera operators stationed at the south end of the property. Each remote case also housed an antenna combiner. These allowed the nodes to connect up to four antenna pairs to the fiber cable which would carry all the signals together to the sound cart. This is a common practice as it eliminates the need to run multiple antenna cables back to the sound cart. An overview of our antenna zones. Fiber recievers on our support cart.