Crystal Filter Design

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SSB6-smaller.png

Design

  • Butterworth, Chebyshev filters
  • Narrow bandwidth bandpass filters for CW or SSB
  • 9 MHz nominal frequency
  • Several crystal filer designs
  • Bin crystals using Colpitts Crystal Oscillator
    • Hand select close values from a pile of crystals

W7ZOI Filters

CW3 Crystal Filter on Kits and Parts Board

  • 9 MHz
  • 330 Hz bandwidth
  • Built onto Kits and Parts board

CW3 P794-720PX.jpg

  • Schematic from W7ZOI paper

XTAL-CW3 Crystals.PNG

  • W7ZOI Measurements

W7ZOI CW3 Measured.PNG

  • Modified K&P schematic

XF2 CW3 SCH.PNG

  • K&P Board

XF2.PCB.png

  • NanoVNA Capture / Analysis

PartsAndKits 9MHz CW3 NanoVNA.PNG

  • Bandwidth
    • 400 Hz -3dB measured
    • 600 Hz -6dB measured

PartsAndKits 9MHz CW3 NanoVNA-BP-Measurements.PNG

CW 5 Crystal Filter on Kits and Parts Board

  • 9 MHz
  • 500 Hz bandwidth
  • Built onto Kits and Parts board

CW5 P792-720PX.jpg

  • Schematic from W7ZOI paper

XTAL-CW-5Crystals.PNG

  • W7ZOI Measurements

CW5 W7ZOI MEASUREMENTS.PNG

  • XF2 Modifications

XF2 CW5 MODS.png

  • K&P Board
    • Cut etch from X2 to X3
    • Cut etch from X4 to X6
    • Add wire across C1
    • Add wire across C8

XF2.PCB.png

  • NanoVNA Capture / Analysis

PartsAndKits 9MHz CW5 NanoVNA.PNG

PartsAndKits 9MHz CW5 NanoVNA-BP-Measurements.PNG

CW3 VS CW5 Filter Comparison

  • 5 KHz span
  • 5 Crystal filter is wider in bandpass but has sharper skirts than the 3 crystal filter

PartsAndKits 9MHz CW3csCW5 SKIRTS NanoVNA.PNG

SSB 4 Crystal

  • Schematic from W7ZOI paper

XTAL-SSB-4Crystals.PNG

  • W7ZOI Measurements

W7ZOI CURVE.PNG

  • XF2 Modifications

XF2 SSB 4 SCH.png

  • K&P Board
    • Cut etch from X2 to X3
    • Cut etch from X4 to X6
    • Add wire across C1
    • Add wire across C8
    • Add wire across C9

XF2.PCB.png

  • NanoVNA Capture / Analysis

PartsAndKits 9MHz SSB4 NanoVNA.PNG

PartsAndKits 9MHz SSB4 NanoVNA-BP-Measurements.PNG

SSB 6 Crystal

XTAL-SSB-6Crystals.PNG

References

Kits and Parts dot Com Crystal Filter Kit

Schematic

XF2.SCH.png

XTAL-CW-5Crystals.PNG

PCB

XF2.PCB.png

Notes

XF2 CW5 MODS.png

  • T1 & T2 are optional matching transformers.
  • Typical transformer type will be a BN-43-2402 using 34 gauge magnet wire
  • C3a,C4a,C5a,C6a are optional trimmer capacitors for fine tuning the crystal filter
  • Typical trimmer caps are GKG50015

Videos

IMSAI Guy Videos

Gregg Messenger VE6WGM

Charlie Morris

  • Jan '21 - Simple SSB Rig: Part 3 - Crystal Filter

  • Mar '20 - CW Rig. Part 1 - Homebrew CW Crystal Filter

  • Aug '18 - Homebrew 80/40m SSB/CW Rig - #4b CW Crystal Filter

  • Jan '18

W2AEW

W0QE

Amateur Radio VK3YE

bill ncham