Jason, After looking at the data sheet in your email, the device shown seems to have only one receive diode, so I/Q is not feasible. This one is one of the cheapo door openers, not the one used for price rada= rs. the one I used had 4 pins, as they had two receive diodes for I/Q mixer. Jean-Paul N1JPL > On Apr 17, 2016, at 5:10 PM, Jean-Paul Louis wrote: >=20 > Jason, > These gunplexer from Macom have been used for a long time to make doppler= radars. > Even know that they were originally intended to be use for door openers, = some companies > in the police radar business used them as the base device in their radar = guns. >=20 > I hope that you took serious care of avoiding ESD because these devices a= re VERY sensitive. > Not the gunn diode, but the two schotky that are the receiver part. >=20 > It is a self mixer, when you power the gunn diode, some of the transmit s= ignal is used as the > LO for the receiver, so you get only the frequency difference (doppler) >=20 > Then you can use a DSP processor to calculate the speed. >=20 > I hope you did not turn the screw as you might have already killed the re= ceive diodes. > There are two of them that provide I/Q signal >=20 > My $0.02, > Jean-Paul > N1JPL >=20 > I worked in one of those police radar companies a long while ago.=20 >=20 >=20 >=20 >=20 >=20 >> On Apr 16, 2016, at 2:34 PM, Jason White wrote: >>=20 >> Hello, Recently I saw a video demonstrating how Gunnplexers are used in >> "Radar Guns" (speed measuring). I bought a 24Ghz gunplexer [1] so that I >> could make my own radar gun. Now that I have see one up close I have som= e >> questions about how they work and what some of the tuning screws do. I h= ave >> attached a photograph to make things easier to explain. >>=20 >> [Question 1]: There are two tuning screws a large brass one and a small >> silver one. What is the function of the silver tuning scew? >>=20 >> The brass one is labeled as the frequency adjust screw, presumably it >> sticks down into some sort of cavity resonator. The second screw, the >> silver one, goes through the case and comes out directly in front of a >> small aperture (hole) coupling the oscillator's output into the waveguid= e. >> Right next to this screw is the mixer diode for the Doppler output. The >> screw came adjusted so that it is even with the lower edge of the >> oscillator aperture. Could this screw have something to do with the amou= nt >> of coupling between the oscillator's output and the mixer diode? >>=20 >> [Question 2]: The oscillator is coupled to the waveguide through a ~1.5m= m >> eliptical hole that is much smaller that the wavelength for 24Ghz (12mm)= .. >> How can the 24GHz from the oscillator pass through such a small hole? >>=20 >> Thanks, >> Jason White >>=20 >>=20 >> [1] M/A-COM: MACS-007801-0M1R10 "24.125 GHz Mono Doppler Transceiver" >> Datasheet: http://cdn.macom.com/datasheets/MACS-007801-0M1R10.pdf >>=20 >> --=20 >> Jason White >> <180.jpg>--=20 >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >=20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .