I think the phenomenon extends from radio waves (long, medium and high) to infrared and ultraviolet. The radar presupposes a single antenna and a delay in the reflected signal, I think that adding a transmitter for example in the FM band increases the sensitivity of the TR2 mixer, but in this way makes it difficult to calibrate. I obtained a good sensitivity using a 20Mhz quartz and tuning the L1/C10 filter on a 20Mhz harmonic. for example 100Mhz (20 X 5) or 120Mhz (20 X 6). Unfortunately the tuning is very critical, out of 3 specimens only one works, the calibration with 8Mhz is already complicated but there is no problem of the harmonics, unfortunately however the 8Mhz harmonics have a level too low to be used.
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