You don't have to use high bandwidth ADCs, in another post Aloha brings up the XTS3000 which uses a ADC/DAC setup that only digitizes about 400KHz of bandwith a

You don't have to use high bandwidth ADCs, in another post Aloha brings up the XTS3000 which uses a ADC/DAC setup that only digitizes about 400KHz of bandwith and it gets along fine as far as power consumption. My main point is that we already do this sort of thing in the radio industry and the RF requirements of the JTRS are not at all far fetched. The issue with the project is the software outside of the actual SDR code. Also, as a little bit of extra trivia, antennas designed for higher transmit power don't have any less performance than equivalent antennas for lower transmit powers. Infact the opposite may be true on HF as you will be more likely to tune (both actively and passively) the antenna you have connected to an HF transceiver than connected to just a receiver.