Build your own cable radar: 10/01/98
Electronic Design - Ideas for Design / A time domain
reflectometer (TDR) is a handy but rather expensive
instrument, and isn’t commonly found on every bench.
I used to rent them, but after having paid large
bills for several years, I decided to make my own. I
saved a bundle and was able to. . .
Economy radar detector
: This circuit uses a 1458 dual op-amp to form
a radar detector. C1 is the detector of the radar
signal. The first op-amp forms a current-to-voltage
converter and the second op-amp buffers the output
to drive the piezo transducer. R5 sets the switching
threshold of the second op-amp; normally it is
adjusted so that the circuit barely triggers on
background noise, then it's backed off a bit. The
response of the circuit may be tuned by adjusting
the length of the leads on C1. For typical
road-radar systems, the input capacitor's leads
should be about 0.5 to 0.6 inches long.