AADE Filter Design is now FREE.
The latest version includes some very interesting crystal ladder filters
using identical crystals.
Both upper and lower sideband filters.
Matched USB and LSB from the same crystal frequency.

To view a short article about these crystal filters see
http://www.aade.com/filter32/dishal.htm

To download the program see: http://www.aade.com/filter32/download.htm

Neil (The L/C Meter IIB guy)
Almost All Digital Electronics