KCBS Transmitter Site

Inside the KCBS Transmitter Building

KCBS AM Harris DX50 and phasor

Here is a shot of the of Main transmitter and the phasor. The transmitter is in the background. It is a 50,000 watt Harris DX50. It was made in 1990 and has been in use for 17+ years. The DX50 has been extremely reliable. This is due to the fact that it is entirely solid state. There are 128 individual power amplifier modules that are turned on and off digitally to make up the carrier wave. The highest voltage in the transmitter is the input AC voltage at 480 volts AC. The transmitter operates at about 230 volts DC with 230 to over 300 amps of current, depending on how loud the audio signal is at that moment (level of 'modulation'). Compare that to our Harris MW50 transmitter that is being removed in this re-build. It had a 25,000 volt power supply with 9200 volts at 6.9 amps on the plate of the tube. That would wake you up if you put your hand in the wrong place.

The four closest cabinets make up our phasor. This box switches between our two transmitters, main and aux, and takes the power from the selected transmitter and divides it up between our four towers. It also changes the phase of the four signals, meaning it alters the amount of time it takes for the power to reach a tower, and the combination of the power level and phase of the signal arriving at each tower allows us to direct the signal where we need it to go and lower the signal level in directions where we need to protect other radio stations.

The copper pipes on the top of the phasor and transmitter are the feedlines that carry the RF power from the transmitters and out to the towers. Behind the phasor you can see part of the transmitter emergency studio. Click here to see what the transmitter emergency studio and newsroom look like.

Previous Page Button gif _2.2 K homepage.gif - 2755 Bytes next Page Button gif _2.8 K

Questions or comments about the tour?
Contact Dave Wigfield at

Updated 01-14-08

©Copyright DRW 2008