The uWSDR (Microwave SDR) will not need a transverter, it will provide a transceiever operating at the frequency of interest (144, 422, 1268, 2400 etc). It will cover the whole of each band - i.e. 1240-1300MHz. Full duplex cross-band products such as L/S are planned specifically for satellite use. The hardware is still in development, but progress is being made, and software can be downloaded now and used either in simulator mode or with a Softrock. The hardware should be available long in advance of the next HEO launch.
Detailed system simulations show that the RF performance will be as good as, and hopefully significantly better than, a transverter/IF combination.
More details on the uWSDR website - fell free to join the project if you so desire, any extra help would be appreciated.
uwsdr.berlios.de
regards
Grant G8UBN for the uWSDR team