That is a good starting point but I'd add much has been published
since then on building crystal filters.
Using the series ladder design and the right constants you can build
USB and LSB filters as well as symetrical. A good source is the ARRL
publication Experimental Methods in RF Design which devotes a fair
amount of text to crystal filters and has a good listing of citings
for further reference.
I've use their techniques to build excellent filters using 6 and 8
crystals with symetrical shapes to greater than 70db and low ripple.
The gausian to 6db shape happens to sound the best to me for 2.2khz
SSB filters. I'm using a 6 crystal version of same in the first
version of BITx I've built as an transverter IF.
Allison
KB1GMX
