21 Mar 2013
What I think is quite an old paper turned up in my browsing today: http://www.norcalqrp.org/files/austinnc2030presentation.pdf . In it, Dan Tayloe N7VE describes how a direct conversion design with phasing to cancel out the unwanted sideband can be a truly excellent receiver. I have never tried this approach myself, but think it would be worth it for, for example, a WSPR receiver where the phase accuracy has only to be maintained over a 200Hz audio bandwidth. Over such a small audio bandwidth a very simple phase shift network would work.The same applies on TX where a very simple final frequency phasing TX could produce quite good sideband suppression with very few parts.