crystal Filter using 3 Inverted Mesa Crystals at 143MHz
Picture of 143MHz crystal filter using inverted MESA
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500kHz span // 50kHz / division
200KHz Span
1MHz span
5MHz span
simulated filter curve using AADE filter design 4.5
schematic of final 142.94MHz filter
crystal equivalent Parameter using DJ6EV program
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I also have made several different crystal Ladder filters using near 200MHz with 1, 2, 3, 4 crystal.
even with 1 crystal, filter Curve is sharper than Inductor / Capacitor with reasonable side, or Helical resonator.
to get similar curve, one have to use Cavity filter like those used in duplexer.
AG6JU
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