These files are for LT_SPICE and run a simulation of the EW Front end (Reference and variable oscillator with antenna components, and diode mixer) - The simulation card is set for 2ms stop time, and the difference frequency set so that the heterodyned output can be viewed.. You could change the simulation to stop at 1ms and still see a few cycles of the difference signal.
Running with lower difference frequency really takes a long time - at least on my old PC it does.
LT_Spice can be downloaded free from http://www.linear.com/
