An important part of setting up a new plant is finding ways to get the program audio (read that music, sports, whatever) from the studio to the transmitter. Years ago, it was impossible to send high quality audio from one place to another, which is why many stations had the studios annd the transmitter in the same place.
At first, it was the phone company and high quality phone lines that carried the programming; later, as the cost of doing that increased while the reliability of the circuits went down, we needed to find another method.
Dedicated microwave links turned out to be the answer. A radio station could buy the equipment (as opposed to renting a phone line) and then avoid the rental charges. Also, the microwave paths were usually more reliable.

But, there are only a limited number of microwave channels available. In a city like Los Angeles, they're all used. Many times, by many different stations. By carefully aiming dishes, and uing mountains to block signals on the same channel, we can use the same frequencies many times.

The microwave system for the new transmitter system is called a 'double hop'. We go from Burbank to Verdugo Peak on 951.1, and then from Verdugo Peak to the City of Industry on 946.0

946.0 is the same channel we use to get from Burbank to Mount Wilson, but because the paths cross each other, they don't interfere.

Similarly, all the stations on 951.5 are going different directions than we are, so we were able to squeeze in the new channels.

For KXTA, the normal path to the transmitter is the microwave. For KIIS-FM, we use a dedicated T-1 digital path to the FM transmitter on Mt. Wilson. This is a two way path - it carries the stereo signal up to Mt. Wilson, along with the remote control information. Coming back down, we have two high-fidelity audio channels for the stereo out of the Megacruiser, a regular audio channel for the traffic reports from the helicopter, and the return metering from the remote control. Even though the T-1 costs about $ 800 a month, it still makes economic sense compared to the cost of the separate lines we'd need without it.

The two main STL (Studio to Transmitter Link) dishes; one goes directly to the FM at Mount Wilson, and the other to Verdugo Peak for relay to the AM transmitter in the City of Industry


The Verdugo Peak Repeater Site; this is where the 951.5 Mhz. signal is received, converted to 946.0 Mhz., and boosted for the trip to the City of Industry


In order to test the new channels and insure they didn't interfere with other stations using the same channels, we built this test rack. It has a 360 Systems 'Instant-Replay' unit, (with a message about who we are and the number to call if we interfere with anyone), and a Moseley PCL-606 transmitter tuned to the frequency for this particular hop. We mailed letters to all the stations on 'our' channels two weeks ahead of time, followed up with a FAX the day before the test began. Luckily, no one called to report problems!



Copyright 2005 by Vital Sounds - ALL RIGHTS RESERVED