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FM Bandpass Filters
2P, 3P Series

RFS bandpass filters are primarily used as part of multi-channel combiner facilities but can also be used to eliminate spurious emissions and increase isolation between co-sited services.
The filters are designed with all bolted connections and any sliding contacts are at low current density points to ensure maximum reliability and ideal power ratings for a given physical size.
Each filter comprises several 2 or 3 coaxial resonators which are aperture coupled. The fixed aperture coupling design is engineered for a constant passband wherever the pass band is tuned in the 87.5 - 108MHz band. This design ensures standard insertion loss and rejection for each filter model, although custom filter performance (modified aperture coupling) is available on request.


  • Natural convection cooling for all power levels
  • Fixed aperture coupling for high reliability and easy re-tuning
  • Vertical entry and exit
  • Invar temperature compensation
  • 2 and 3 pole versions standard

Typical FM bandpass filters

Technical features

General Specifications

Product LineFilters
Product TypeBand II (VHF) FM Bandpass Filter
Filter type3 Pole

Electrical Specifications

Frequency Range (tuneable) MHz87.5 - 108
Input Power (maximum), kW AveragekW2
Insertion Loss at Channel Centre Frequency dB0.5
Input Return Loss dB> 26 to ± 200kHz
Input Group Delay Variation Over Channel Bandwidthnsec< 25 to ± 100kHz
Amplitude Variation dB< 0.2 to ± 200kHz
Filter Rejection dB20 at 0.8MHz
38 at 1.6MHz
Impedance Ω50

Mechanical Specifications

Weight, Kg (lb)kg (lb)45 (99)
Dimensions (Height or Length), cmcm (in)140.0 (55-1/8)
Dimensions (Width) cm (in)30.0 (11-3/4)
Dimensions (Depth) cm (in)80.0 (31-1/2)

External Document Links


  • Note 1 Alternative connectors available on request.