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
    • Can get much closer than 10% of bandwidth with 50 crystals

W7ZOI Filters

CW3 Crystal Filter on Kits and Parts Board

  • 9 MHz nominal
  • Measured values
    • 8.997836
    • 8.997836
    • 8.997838
  • 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 nominal
  • Measured values
    • 8.997782
    • 8.997783
    • 8.997784
    • 8.997784
    • 8.997785
  • 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 Filter on Kits and Parts Board

  • 9 MHz nominal
  • Measured values
    • 8.997800
    • 8.997801
    • 8.997802
    • 8.997803
  • 2KHz bandwidth
  • Built onto Kits and Parts board
  • 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 X1 to X2
    • Add wire across C1
    • Add wire across C8
    • Add wire across C9
    • Install X1 at X1a position

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

Sorted 9 MHz Crystals

  • Bought 50 crystals
  • Marked with numbered labels
  • Mouser #: 449-LFXTAL064523BULK
  • Mfr. #: LFXTAL064523Bulk
  • Mfr.:IQD
  • Description: Crystals 9MHz 30pF -10C 60C
  • Datasheet
Number Freq Delta Freq Abs delta f
33 8.997668 -130.7 130.7
43 8.997704 -94.7 94.7
17 8.997707 -91.7 91.7
42 8.997707 -91.7 91.7
40 8.997726 -72.7 72.7
03 8.997733 -65.7 65.7
36 8.997742 -56.7 56.7
23 8.997753 -45.7 45.7
25 8.997755 -43.7 43.7
05 8.997761 -37.7 37.7
27 8.997767 -31.7 31.7
15 8.997776 -22.7 22.7
39 8.997782 -16.7 16.7 CW5
35 8.997783 -15.7 15.7 CW5
10 8.997784 -14.7 14.7 CW5
18 8.997784 -14.7 14.7 CW5
04 8.997785 -13.7 13.7 CW5
20 8.997788 -10.7 10.7
49 8.997788 -10.7 10.7
09 8.997791 -7.7 7.7
12 8.997791 -7.7 7.7
41 8.997793 -5.7 5.7
06 8.997794 -4.7 4.7
21 8.997798 -0.7 0.7
38 8.997798 -0.7 0.7
07 8.997800 1.3 1.3
32 8.997800 1.3 1.3 SSB4
14 8.997801 2.3 2.3 SSB4
47 8.997802 3.3 3.3 SSB4
34 8.997803 4.3 4.3 SSB4
08 8.997809 10.3 10.3
30 8.997810 11.3 11.3
48 8.997812 13.3 13.3
50 8.997814 15.3 15.3
31 8.997818 19.3 19.3
46 8.997822 23.3 23.3
22 8.997825 26.3 26.3
26 8.997836 37.3 37.3 CW3
44 8.997836 37.3 37.3 CW3
28 8.997838 39.3 39.3 CW3
02 8.997840 41.3 41.3
45 8.997840 41.3 41.3
29 8.997846 47.3 47.3
19 8.997851 52.3 52.3
01 8.997858 59.3 59.3
24 8.997858 59.3 59.3
11 8.997868 69.3 69.3
16 8.997872 73.3 73.3
13 8.997879 80.3 80.3
37 8.997937 138.3 138.3
Average 8.997799 Deviation 36.34

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