• Low VSWR
• Low Insertion Loss
• High Isolation

Dielectric's FM Combiner is used when it is necessary to combine two FM channels into a single master antenna. Dielectric's combining systems are designed in modular fashion. The diplexing module is the fundamental building block. By cascading additional modules, new stations may be added.

Depending on frequency, spacing, and on desired isolation, either branch or constant impedance design will be used.

Electrical Data

*55 dB possible, contact factory.

Branch Diplexer

Constant Impedance Module

Mechanical Data

General Description

Dielectric's FM multistation combiners are designed to provide maximum isolation between input ports with minimum insertion loss and input VSWR. Most combiner systems are configured as a balanced (constant impedance) multiplexer to maintain optimum system performance and accommodate channel spacings of 0.8 MHz. Band reject style and/or band pass style cavities are employed to allow similarity of modules and the 0.8 MHz spacing.

By leaving the first broadband input port open, an emergency port is available to bypass a module or add a new frequency (station) with additional external filtering. Forward and reverse power monitoring can be provided for systems measurements and transmitter protection.

The Dielectric multiplexer is normally quoted complete with optional switching packages to provide individual transmitter testing and/or combining module bypass capability. Switching systems utilize Dielectric's motor driven or manual patch panels and can be pre-assembled (rack mounted) or rail-mounted in the ceiling.

Typical Specifications

Typical Electrical Schematic

Switcher/Combiner

The Dielectric combiner/switcher is designed to combine two same channel FM transmitters, phased 90 degrees apart, to a common output port. In the event of a transmitter failure, bypass capability is provided with motor driven switching which places one transmitter to air and the failed transmitter to the station load. The station combiner reject loads are supplied in the standard rack assembly. Two 4 port and one 3 port motor driven switches (sized per power requirement) are utilized. Supplementary filtering to reduce spurious emissions can also be provided.

Forward, reverse and reject load power monitoring points are included in the standard unit. Primary voltage and control voltage inputs plus monitoring outputs use single or multipin connectors for ease of installation and maintenance. The FM combiner/switcher is shipped as a fully assembled unit.

Switchless Combiner

• Switch Transmitters Under Full Power
• High Efficiency
• Increased Reliability

The Dielectric Switchless combining system provides a reliable and convenient alternative to conventional coaxial switches for the combining of two transmitters. All mode changes are accomplished simply by moving a dielectric block from its parked position inside the phase shifter. The signal is delayed through the phase shifter and this phase difference is responsible for the switching function within the combiner. With all moving contacts removed from the RF path, reliability is increased and the combiner can be switched under full power.