1) “Dishal” by DJ6EV
This software takes into account crystal parallel capacitance (Cp).
Crystal Cp is a reason for crystal ladder bandwidth narrower than designed in theory.
You need to provide crystal series resonance frequency and crystal inductance Lm or capacitance Cm. If you cannot measure Cp, you can assume value of 4pF.
”Dishal” includes set of useful tools for computing:
- crystal parameters using G3UUR method
- crystal parameters using 3dB method
- LC impedance match
- transforming series LC circuit into parallel one
- fine tubing crystal in a filter using series capacitance (moving resonance up)
‘Dishal’ computes Chebyshev and Butterworth designs, it also contains module for Cohn filters.
I used crystal with relatively low Lm and high Cm and filters computed with his software had slightly narrower bandwith than designer. Anyway I recommend ‘Dishal’ for most applications.
URL: http://fa-nwt.akadns.de/blogs/media/blogs/dj6ev/quarzfilter/deDishal2026.zip
Article with program description and good practical advices: http://www.arrl.org/files/file/QEX_Next_Issue/Nov-Dec_2009/QEX_Nov-Dec_09_Feature.pdf
2) “AADE Filter Design and Analysis”
Software for designing many types of filters – not only crystal ladder.
It requires to specify many crystal parameters. But practical implementation of computed filter has parameters closely matching designed values.
It can design any type of crystal Lauder filter.
I used AADE to design my home made crystal filters for Elecraft K3 transceiver.
The help file is very good, you shouldn’t start work with AADE without Reading the tutorial
URL: http://www.aade.com/filter.htm
3) LCFD – “Ladder Crystal Filter Design” by UA1OJ
Crystal parameters are determined using G3UUR method
I haven’t tested filters designed with this software. Determining crystal parameters is working fine.
LCFD can design Chebyshev and Butterworth filters.
URL: http://www.cqham.ru/lcfd.htm
Tags: crystal filters, crystal ladder, design
