CY321 UHF Switchless Combiner
The CY321 is a coaxial UHF switchless power combiner that combiner two (2) UHF transmitters into a single output. The system includes a motorized three-position phase shifter. This is a compact floor mounted unit that can combine two power amplifiers of up to 7.5 kW each for combined output power of 15 kW.
The desire for higher transmitter output power and reduced OFF-air time during transmitter switching, has led to the development of the UHF switchless combining system. This unit is normally used to combine the output of two parallel transmitters, which doubles the output power over a single transmitter. Should either of the individual transmitters fail or require maintenance, that transmitter can be routed to the station load without disrupting the signal to the antenna.
NOTE: The performance of maintenance on a down transmitter while the other transmitter is on power is not recommended from a personnel safety standpoint.
The UHF switchless combining system consists of two 3 dB hybrids and a common case 0-180 degree phase shifter that provides a continuous RF path while varying the electrical lengths of the transmission lines. Since the electrical paths are not interrupted, the transmitters are not required to be turned OFF during switching operations.
A metal frame is utilized to house and support the various components used to make up the switchless combiner system. The RF inputs and outputs to the unit are located on the top of the unit for easy access. The Control Circuits for the switchless combiner system are housed in an electrical enclosure to prevent exposure to the operating voltages used in the system.
A self-contained control circuit is provided to control the switchless combiner system. The control circuits are directed by signals from the transmitter control system. When a change of mode command is received, the switchless combiner control circuits will cause the phase shifter to initiate a change in position. When the phase shifter has reached the intended position, the switchless combiner control circuits will de-energize the linear actuator that drives the phase shifter and provide status signals back to the transmitter control system indicating that the switchless combiner system is now in the commanded position.
The system provides the following operating modes:
Cabinets A and B to air
Cabinet A to air and Cabinet B to reject/test load
Cabinet B to air and Cabinet A to reject/test load
The switching between modes is driven by the phase shifter and can be done under power without interrupting transmission.
