Coax Filter Designer

Design notch and bandpass filters using coaxial transmission lines.

0.1 to 1000 MHz
Auto from cable (modify for custom cable)

Stub length is the physical coax length needed. Use quality connectors and low-loss cable. VF varies by cable type—check your datasheet.

Stub Configuration Quick Reference

Practical Build with T Connector (SO-239):

• Connect Radio → T connector → Antenna (two axial ports)
• Connect stub to the perpendicular T port (shunt configuration)
• Use short-circuit (both ends connected) or open-ended (one end floating) as needed

Notch Filter (Reject): Short-circuited stub in shunt → blocks center frequency, passes all others

Bandpass Filter (Pass): Short-circuited stub in shunt → passes center frequency ± BW, rejects outside

⚠️ Short-circuited: Both ends connected (more robust, weatherproof)
⚠️ Open-ended: One end floating (resonant at specific frequency, can collect moisture)