Crystal Filter Design
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Contents
W7ZOI Filter Builds
- W7ZOI Crystal Filter paper has several crystal filter designs
- Narrow bandwidth bandpass filters for CW or SSB
- Used for transmit/receive
- 9 MHz nominal frequency
- 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
- Use Kits and Parts Crystal Filter (XF2) cards for 3-5 crystal filters ($4 each)
- Needs some cuts/jumpers
- 9 MHz Filters With Inexpensive Crystals - W7ZOI paper
CW3 Crystal Filter on Kits and Parts Board
- 9 MHz nominal
- Measured values
- 8.997836
- 8.997836
- 8.997838
- 330 Hz bandwidth
- 50 Ohms in/out - no transformers needed
- Built onto Kits and Parts board
- Schematic from W7ZOI paper
- W7ZOI Measurements
- Modified K&P schematic
- K&P Board
- NanoVNA Capture / Analysis
- Bandwidth
- 400 Hz -3dB measured
- 600 Hz -6dB measured
CW 5 Crystal Filter on Kits and Parts Board
- 9 MHz nominal
- Measured crystal values
- 8.997782
- 8.997783
- 8.997784
- 8.997784
- 8.997785
- 500 Hz bandwidth
- Input output transformer
- 50:200 Ohms
- 10 bifilar turns #28 on FT-37-43
- Built onto Kits and Parts board
- Schematic from W7ZOI paper
- W7ZOI Measurements
- XF2 Modifications
- K&P Board
- Cut etch from X2 to X3
- Cut etch from X4 to X6
- Add wire across C1
- Add wire across C8
- NanoVNA Capture / Analysis
CW3 VS CW5 Filter NanoVNA Comparison
- CW3 = 330 Hz bandwidth
- CW5 = 500 Hz bandwidth
- 5 KHz span
- 5 Crystal filter is wider in bandpass but has sharper skirts than the 3 crystal filter
SSB 4 Crystal Filter on Kits and Parts Board
- 9 MHz nominal
- Measured crystal values
- 8.997800
- 8.997801
- 8.997802
- 8.997803
- 2KHz bandwidth
- Input output transformer
- 50:200 Ohms
- 10 bifilar turns #28 on FT-37-43
- Built onto Kits and Parts board
- Schematic from W7ZOI paper
- W7ZOI Measurements
- XF2 Modifications
- 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
- NanoVNA Capture / Analysis
SSB 6 Crystal
References
- Crystal ladder filters – Software
- Crystal Ladder Filters for All - ARRL QEX
- DISHAL software by DJ6EV
- A Practical Test Set for Comprehensive Crystal Testing
- Crystal characterization and crystal filter design
- Crystal parameters Written by Hans Summers
Kits and Parts dot Com Crystal Filter Kit
Schematic
PCB
Notes
- 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
Parts
Caps
| Capacitance (pF) | Mfr. # | Manufacturer | Description |
|---|---|---|---|
| 10 | S100K33SL0R63K7R | Vishay | Ceramic Disc Capacitors 10pF 3000V 10% SL0 7.5mm LS |
| 33 | CC45SL3AD330JYNNA | TDK | Ceramic Disc Capacitors D: 5.5mm 1kV 33pF SL 5% LS:5mm |
| 47 | CC45SL3AD470JYVNA | TDK | Ceramic Disc Capacitors D: 5.5mm 1kV 47pF SL 5% LS:5mm |
| 82 | CC45SL3AD820JYNNA | TDK | Ceramic Disc Capacitors D: 6mm 1kV 82pF SL 5% LS:5mm |
| 100 | CC45SL3AD101JYNNA | TDK | Ceramic Disc Capacitors D: 6.5mm 1kV 100pF SL 5% LS:5mm |
| 120 | CC45SL3AD121JYNNA | TDK | Ceramic Disc Capacitors D: 7mm 1kV 120pF SL 5% LS:5mm |
| 200 | S201K33S3NN63L6R | Vishay | Ceramic Disc Capacitors 200PF 1KV 10% |
| 270 | CC45SL3AD271JYVNA | TDK | Ceramic Disc Capacitors D: 9mm 1kV 270pF SL 5% LS:5mm |
| 330 | S331K33Y5PR63K7R | Vishay | Ceramic Disc Capacitors 330pF 3000V 10% Y5P 7.5mm LS |
| 390 | CC45SL3AD391JYVNA | TDK | Ceramic Disc Capacitors D: 10.5mm 1kV 390pF SL 5% LS:5mm |
| 470 | D471K20Y5PH6UJ5R | Vishay | Ceramic Disc Capacitors 470pF 100V 10% |
| 680 | S681K29Y5PN63J5R | Vishay | Ceramic Disc Capacitors 680pF 1000V 10% Y5P 5.0mm LS |
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 |
