Hi: RF Space is developing the SDR-IP (Internet Protocol) receiver that has options for an external 10 MHz Cesium reference as well as 1 PPS input to allow multiple receivers to work as RADAR sets (using FM radio broadcast transmitters) or for radio astronomy. http://www.rfspace.com/SDR-IP.html http://groups.yahoo.com/group/SDR-IP/ The existing SDR-IQ and SDR-14 are now being used in a number of space related activities, see: http://www.rfspace.com/BLOG/BLOG.html -- Have Fun, Brooke Clarke http://www.prc68.com