Look at http://www.g4jnt.com/SDR_Projects.htm and http://www.g4jnt.com/LFUpconv.pdf
Thatwas desihned specifically for WSPR at LF, and could be used at higher frequencies with suitable LO driving it. Andy www.g4jnt.com > I've recently been intrigued by WSPR weak signal HF mode, and > immediately started thinking of a simple transmitter that would allow > me computerless beaconing. > > What I need is a USB transmitter on a very narrow 30m frequency range > (1 kHz) for a narrow bandwidth signal (<10 Hz). This requirement > differs from all other approaches that seek as much wideband as > possible. >
