Bandpass Filter Utility

Try out our bandpass filter utility. Unique to our site this utility can generate simulated graph responses in a wide variety of selections. DCI can manufacture many of the possible configurations.

Center Frequency

Center frequency can be between 2 and 18000 MHz. DCI typically makes filters between 30 and 6000 MHz.


Increasing bandwidth reduces insertion loss. Bandwidth can be up to 50% of the center frequency. Typical DCI filters have bandwidths up to 14% of center for VHF and 20% of center for UHF.


Q is the quality factor of the filter; increasing Q reduces insertion loss and improves overall performance. Q can be between 100 and 25000. The higher Q is, the larger the filter will be. DCI filters typically have the following set values:
  • 3500 for VHF
  • 7000 for UHF
  • 5000 for Milled Cavity Filters
  • 10000 for 4.25" Extruded UHF Filters
Note: Some custom filters can be as high as 25000.


SWR can be selected in a range from about 1:1 (butterworth) to about 2:1. DCI typically manufactures filters with about 1.2:1 SWR which is equal to 20.8dB return loss.

Graphing Span

Graphing span (the horizontal range being graphed) can be between 1 and 16 times the filter bandwidth. This helps you see more detail in the generated filter graphs.


Poles are also known as cavities, or the filter's "order". Increasing the number of poles increases the filter's isolation, but also increases loss.

Filters with between 2 and 12 poles can be manufactered, but DCI tends to build the majority of our filters with 4, 6, 8, 10 or 12 poles.
Marker Frequency
There are four entry fields for markers. Insert any value in MHz to obtain a loss value in dB.

These will help determine what kind of filter is needed to pass or reject certain frequencies.
Marker 1: MHz dB
Marker 2: MHz dB
Marker 3: MHz dB
Marker 4: MHz dB

DCI Digital Communications Ltd.

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