I've been working on an SDR (Software Defined Radio) receiver that I can control via computer so I can use my TV receiver dongle to work linear transponder satellites. It hasn't work or, rather, has kind of worked strangely so last night I took it apart, metaphorically, and experimented with locally-generated signals so I could try to figure out what was going on. Having identified the errors, corrected those errors, and tested the correction, I can now explain how to make one of those things that works. The receiver part, anyway.