5-Pole Bessel Low Pass Filter 15 MHz 50 Ohm In/Out RF Card Handmade PCB

5-Pole Bessel Low Pass Filter 15 MHz 50 Ohm In/Out RF Card Handmade PCB

This is a hand-built 5-pole Bessel low pass filter constructed on a perforated copper-clad PCB, designed to pass signals below 15 MHz while attenuating higher frequencies. The filter uses a Bessel topology, which is chosen for its maximally flat group delay characteristic — meaning it preserves the shape of waveforms passing through it better than Butterworth or Chebyshev designs at the cost of a less steep rolloff. Input and output impedance are 50 ohms, matching standard RF and coaxial systems. The card is hand-labeled "5-pole Bessel 15MHz" with IN and OUT marked directly on the board.

Specifications & What's Included

• Filter type: Bessel low pass
• Number of poles: 5
• Cutoff frequency: 15 MHz
• Input impedance: 50 ohms
• Output impedance: 50 ohms
• Construction: hand-built on perforated copper-clad PCB
• Connectors: two SMA-style connectors (IN and OUT), mounted on the top side of the board
• Passive components: visible ceramic capacitors and axial leaded inductors/resistors hand-soldered to the board
• Form factor: bare PCB card, no enclosure
• Hand-inked labeling on top side: "5-pole Bessel 15MHz", "IN", "OUT"

Applications

Bessel low pass filters are used in RF and analog signal processing wherever preserving the time-domain shape of a waveform matters more than achieving a sharp frequency cutoff. At 15 MHz with 50-ohm termination, a filter of this type is suited for lab bench use, RF signal conditioning, baseband signal cleanup, pulse shaping, and test fixture work. A 5-pole Bessel design provides a smooth, linear phase response through the passband, making it a common choice in oscilloscope front-end circuits, data acquisition signal chains, video bandwidth limiting, and RF instrumentation setups. Hand-built filters like this one are common in RF lab and research environments where a specific response shape is needed quickly without sourcing a commercial unit, and they find use by engineers, students, and hobbyists working on custom RF test setups, amateur radio projects, and signal integrity work.