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I was thinking about experimenting with radar.I can't seem to find any good info on it though such as a circuits, frequency or ic chips I might use.Does anyone have anything or know where to get it?
I was thinking about experimenting with radar.I can't seem to find any good info on it though such as a circuits, frequency or ic chips I might use.Does anyone have anything or know where to get it?
As suggested a search should show up tons of data. However before you get too committed to the idea you might consider the legality of any practical radar. Power over a few milliwatts requires licencing and approval in most countries and radar is not a low power application in my opinion.
I'm thinking about radar like the police use to check the speed of a vehicle.
I would be very interested in that toy radar gun Sceadwian suggests but can't buy one just to take it apart and tinker. If someone has already done so and found any important info ,such as ICs used ,maybe they could post it. I get a lot of info on stuff sometime just by getting the numbers off the chips and Googling them.
Found a great site here, gives a complete breakdown on how police radar works, and has a calculator at the bottom to find out different values for different conditions. Click on the links throughout the page to find out more as you read though it http://hyperphysics.phy-astr.gsu.edu/hbase/sound/radar.html
years ago (10-15) electronics now or popular electronics had a project to build a radar ubit, you may want to dig thru their archives to find that project.
With a radar the IC's aren't the problem, it's the RF amp and the oscilator. You're never going to find anything reasonably priced aside from something like the hotwheels gun. Even those are REALLY low power. If you really want to play around with radar physical construction is a KEY element, as you can't just use the same old stuff that works with most other hobby equipment. Even a few extra inches of wire will completly ruin the functionality of the circuit.
With a radar the IC's aren't the problem, it's the RF amp and the oscilator. You're never going to find anything reasonably priced aside from something like the hotwheels gun. Even those are REALLY low power. If you really want to play around with radar physical construction is a KEY element, as you can't just use the same old stuff that works with most other hobby equipment. Even a few extra inches of wire will completly ruin the functionality of the circuit.
This is quite true. I used to repair police radar guns back in my early career days (ie. 1975) and then later on built one of my own, albiet crude, version. Back then they were all X band and the RF front end was simple in principle, but hard to build. So most of us would buy a surplus Xband transceiver which consisted of a waveguide section about an 2 inches long that included a gunn diode mount inside, and a detector diode mount behind that. You used to be able to find them for about $20 back then. I built up a horn antenna from pcb sheets. When you powered this setup, you could scope or amplify the doppler frequency off the detector diode so the circuitry you had to add was audio/digital baseband circuits which were easy. Range wasn't as good as the commercial ones, but definitely better than 100 yards.
Ramsey kits also sells a homemade radar gun kit that uses coffee cans as the antenna. I'm not sure about how they control frequency, as I do not recall that they used a die-cast oscillator/receiver horn with Gunn diode like the commercial units.
30 years ago you could buy the die-cast oscillators from Amperex, Alpha, and others for about $50 to $100, depending upon power and other parameters. I presume somebody is still selling them.
You can also scrounge the oscillator/horn out of a radar based intrusion detector. The microwave part is similar or identical to the heart of a radar gun. I picked up half a dozen units that had been stripped out of a building for about $5 or $10 each a decade or two ago at a building salvage place. Worked fine.
The nice part of the die-cast assemblies is that you only have to supply (very stable) +5 volts (typically) and the module puts out the detected doppler frequency on another pin. Ultra-simple, except that tuning with your horn is critical. We had a devil of a time getting more than a little range across the lab until we accidentally hit on the correct setting of the tuning screw that determines the transmit/receive ratio. When we hit the sweet spot on the tuning screw setting, suddenly we could detect cars a block away with ease. We fabbed a straight-sided rectangular horn about 9" long out of brass sheet and tiny brass angles purchased from a hobby shop.
I realize that five years has gone by since this post but....I recently purchased an Amperex DX489 die-cast antenna. if awright is still around, or anyone else for that matter, do you have a circuit as you described that I could experiment with my DX489?
Still here, but preoccupied elsewhere measuring railroad rails.
Do you have a data sheet for your radar module? That is always the first step in applying any unfamiliar device. If you cannot obtain one elsewhere, let me know. I MAY have a data sheet buried under 40 years accumulation of literature, but definitely do not want to launch a search unnecessarily. The spec sheet should give you critical information about voltage and current required and may also provide recommended circuits and horn design principles.
There's really not much involved in applying the modules. Apply power (closely regulated) ;only after you know exactly what is required and get a Doppler signal out. It's then up to you what you want to do with the Doppler signal. It will be a weak squeaking in the audio frequency range with the amplitude and frequency dependent upon what is moving within its beam and how fast. Amplitude is highly variable and dependent upon the strength of the radar return signal, i.e., how large and close the moving target is.
We used our units for measuring vehicle speeds during acoustic noise surveys and, as described in my old post, after frustrating screwing around with the circuitry, after hitting the tuning sweet spot we were able to get useful speed indications off cars several blocks away. On one test, we were able to get speed indications off transit vehicles approaching around bends in tunnels long before they were visible around the bend. Undoubtedly a slam dunk for the radar due to absence of interference from other vehicles, but still impressive (and fun).
As I recall, we tried used an automatic gain control chip but ended up using a fixed gain op-amp circuit on the doppler signal and just allowed it to clip high signals. If I was to do it again I would definitely use a log amplifier IC to handle the large dynamic range of the Doppler signal without danger of bizarre waveform distortions that some overloaded op-amps create. You do get waveform distortion out of a log amp due to the compression of sine wave peaks, but they are clean and do no harm in the subsequent circuitry.
If you are looking for a speed indication, you can apply the compressed signal out of the log amp to an F-to-V converter chip and apply the output of that to a meter with suitable buffering and voltage/current scaling. It may also be feasible to apply the signal to a tachometer mode digital panel meter but I have not tried that. Then you would have to figure out the conversion from frequency to speed in handy units. In professional units they use processing circuits that compare and average several readings frequency readings to verify them before displaying the result.
Remember that the Doppler signal does not contain direction information so, in the absence of special processing to generate an offsetting frequency, you can't distinguish approaching from receding targets.
The size of your horn aperture strongly affects the narrowness of your beam and, therefore, your ability to focus on a specific target among general traffic. The larger the aperture the narrower the beam. The stubby 1" or so horns commonly supplied with the radar modules are intended for intrusion detection applications and provide almost no directionality. As I recall, the horn I fabbed from brass sheet and angle from the hobby shop was about 10" long and about 5" across the mouth and provided good directionality. Research radar horn design, as aspect ratio and flare rate affect your results.
Excellent information. Thank you. The module I have is an Amperex DX489 die cast microwave oscillator. The markings on the side which identify the three posts on the top of the unit are 'A.F.' -E and +7V. Following that is 'CL 8960'. The unit was made in England, 75-26.
I have bought some old x band commercial police radar units on ebay 5 years ago and I also bought just the horn units.
I would love to have a way to interface the unit to a arduino and have the arduino trigger a ipcam to snap a photo and email the photo with the speed.
I wish I cold get my hands on some schematics.
Theres 2 basic kinds of radar, reflection and chirp.
Reflection is used to measure distance, but if you take multiple measurements over time you can calaculate the change in distance over time which equals speed.
You transmit a pulse which can be sound or rf (usually microwave), then after the pulse is transmitted measure the time it takes for the pulse to be received again after its reflected from the target, this tells you the distance times 2 (there and back).
Chirp radar is more complex and transmitts a sliding frequency range either up or down, the relected signal will be shifted in frequency, up if the target is comming towards you, or down if moving away, and the time taken from the start of the transmission to receiving the reflection is the distance as before, this method is quicker and more accurate and only requires 1 'ping'.
The hotwheels radar gun looks like a load of fun, the only thing is that all the 'doings' are in a metal can.
There is RADAR and there is RADAR. True the police, aircraft and marine all have maggies and stuff for UHF and even some SHF, but if you go back a few years (decades) you will find RADAR on 6 meters 50 MHz and hi VHF 220MHz. I think the Pearl Harbor system was (from the looks of the antennas) in the 70 MHz range.
Today we have OTH (Over the Horizon) RADAR in the 16 MHz bands. USSR did a lot of work in the 70 and '80's. Caused a great deal of QRM aka woodpecker from the sound it made. If you get an Amateur license, you can probably find some of these bands that are available for experimentation. Transmitters are readily available as well as receivers. With modern circuits the timing should be a breeze.
Let us know how you make out.
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