Basic experiment of cryistal filter
I made and take a data of some radder type crystal filters. All of them
are made as LSB type called in Japan. In order to display the charactor
of them clear , I defined the shapefactor and band pass as follows. It
is my oun definition. It is different from that of usual proffesional.
See the figure 1 !
Sｈａｐｅｆａｃｔｏｒ＝(ｆ１／ｆ２）*100%
f1=band width
All is made by the same crystals 10.645MHz.
I tryed the following 6 types.
1.Fig2 : 1 crystal : poormans filter (called by W1FB)
2.Fig3 : 2 crystals : Basic type
3.Fig4 : 4 crystals : Basic type
4.Fig5 : 4 crystals : with bigger capacitor
5.Fig6 : 4 crystals : with more bigger capacitor
5.Fig7 : 4 crystals : with smaller capacitor
水晶フィルターの基礎的実験
ＬＳＢタイプのラダー型水晶フィルターをいくつか製作して、その特性を計っておみせします。個人的なここだけの定義として、シェイプファクターと帯域幅を以下の如く定義します。これは、プロの定義とは異なりますが、目安として用いています。図１をご覧ください。ここで、ピークの１０分の１の振幅の周波数幅を帯域幅ｆ１、１０分の１と１０分の９の帯域幅の割合をシェープファクター（形状比）として、定義します。
以下の６タイプのフィルターを試作して、特性を調べました。尚、全て１０．６４５ＭＨｚの同じ水晶で作りました。
１．図２：水晶１個のフィルター（貧乏人フィルター）
２．図３：水晶２個のフィルター
３．図４：水晶４個のフィルター
４．図５：水晶４個のフィルター（より大きなコンデンサーの場合）
５．図６：水晶４個のフィルター（さらに大きなコンデンサーの場合）
６．図７：水晶４個のフィルター（より小さなコンデンサーの場合）
fig1. Figure indicate the definition of this page.
図１：このページの定義を示す説明図
1.single christal filter(fig2)
| point No. | frequency | volt | gain |
| No. | MHz | V | dB |
| 1 | 10.62337 | 0.06 | -20 |
| 2 | 10.64392 | 0.54 | -0.9 |
| 3 | 10.64510 | 0.6 | 0 |
| 4 | 10.64641 | 0.54 | -0.9 |
| 5 | 10.65474 | 0.06 | -20 |
charactor
*impedance 500ohm (min on the center of band)
*band width f2=2.49kHz
*shape factor 8%
*ripple non
*this filter is good for AM receiver.
2.double christal filter(fig3)
| point No. | frequency | volt | gain |
| No. | MHz | V | dB |
| 1 | 10.63578 | 0.055 | -20 |
| 2 | 10.64400 | 0.5 | -0.9 |
| 3 | 10.64488 | 0.55 | 0 |
| 4 | 10.64592 | 0.53 | -0.3 |
| 5 | 10.64628 | 0.54 | -0.1 |
| 6 | 10.64696 | 0.5 | -0.9 |
| 7 | 10.65083 | 0.055 | -20 |
charactor
*impedance 82ohm (min on the center of band)
*band width f2=2.96kHz
*shape factor 20%
*ripple in the passband 0.3dB
*this filter is good for simple ssb receiver.
3.tetriple christal filter(fig4)
| point No. | frequency | volt | gain |
| No. | MHz | V | dB |
| 1 | 10.64309 | 0.05 | -20 |
| 2 | 10.64441 | 0.45 | -0.9 |
| 3 | 10.64484 | 0.5 | 0 |
| 4 | 10.64564 | 0.43 | -0.13 |
| 5 | 10.64650 | 0.5 | 0 |
| 6 | 10.64693 | 0.45 | -0.9 |
| 7 | 10.64786 | 0.05 | -20 |
charactor
*impedance 27ohm (min on the center of band)
*band width f2=2.52kHz
*shape factor 52%
*this filter is good for ssb receiver and transmittor.
4.tetriple christal filter(fig5)with bigger chapacitor
| point No. | frequency | volt | gain |
| No. | MHz | V | dB |
| 1 | 10.64319 | 0.04 | -20 |
| 2 | 10.64408 | 0.36 | -0.9 |
| 3 | 10.64509 | 0.4 | 0 |
| 4 | 10.64555 | 0.36 | -0.9 |
| 5 | 10.64618 | 0.058 | -20 |
charactor
*impedance 21ohm (min on the center of band)
*band width f2=1.47kHz
*shape factor 49%
*this filter is used for narrow filter of ssb receiver.
5.tetriple christal filter(fig6)with more bigger chapacitor
| point No. | frequency | volt | gain |
| No. | MHz | V | dB |
| 1 | 10.64350 | 0.02 | -20 |
| 2 | 10.64373 | 0.18 | -0.9 |
| 3 | 10.64395 | 0.2 | 0 |
| 4 | 10.64405 | 0.18 | -0.9 |
| 5 | 10.64473 | 0.02 | -20 |
charactor
*impedance 40ohm (min on the center of band)
*band width f2=0.32kHz=320Hz
*shape factor 26%
*this filter is good for special narrow filter of cw receiver.
6.tetriple christal filter(fig7)with smaller capacitor
| point No. | frequency | volt | gain |
| No. | MHz | V | dB |
| 1 | 10.64219 | 0.05 | -20 |
| 2 | 10.64493 | 0.40 | -1.9 |
| 3 | 10.64668 | 0.35 | -3.1 |
| 4 | 10.64848 | 0.55 | 0 |
| 5 | 10.64906 | 0.50 | -0.9 |
| 6 | 10.65014 | 0.05 | -20 |
charactor
*impedance 82ohm (min on the center of band)
*band width f2=4.13kHz
*shape factor 52%
*this filter is good for am and narrow fm receiver.
Settlement is as follows. The more element of crystal makes the more better shape factor. The bigger capacitor makes the narrower bandwidth. Input impedance of this type of crystal filter is anyway some ten ohms. Impedance is changed in the band. Minimum impedance happens on the center of bandwidth.
まとめは，以下のようです．水晶の素子数が多くなると，シェープファクター（形状比）はより改善されます．より大きいコンデンサーは，より狭い帯域幅を作ります．とにかくこの型の水晶フィルターは，数１０オームの入力インピーダンスを示します．入力インピーダンスは，バンド内で激しく変化します．帯域内のほぼ中央で、最小のインピーダンスとなります．
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