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Energy84
July 19th, 2002, 02:10 AM
I know this doesn't have anything to do with the general topics here at the forum (unless we are more advanced than I suspect :rolleyes: ) but the subject has been bugging me lately, I want to build my own working radar system.
It's not necessarily going to be a full featured tracking system, but just something simple enough to detect a vehicle or something at long ranges (1-2 miles, mabye more, mabye less) and also be able to tell speed and distance. I think it should be easy enough to set up, in theory. I figure that I could use the BASIC Stamp 2p from <a href="http://www.parallaxinc.com/html_files/products/Basic_Stamps/module_bs2p.asp" target="_blank">Parallax</a> to handle all the number crunching required to determine ranges and display the information. It wouldn't be that hard I don't think to program the thing.
My biggest handicap right now is the transmitter/receiver portion of it. I haven't got a clue how this would be setup. The only place I can even think of to get a transmitter and receiver is from a police radar detector with jamming feature. The radar detecting portion of the device is supposed to be a receiver, and the jamming feature is supposed to be a transmitter. All that would need to be done is to disassemble the unit and figure out how to rewire it to suit my needs. Or at least that's the plan.
Also, I believe that the signal would need to be focused somehow. This task I think would be best accomplished by using a small satellite dish (24" RCA dish should suffice).
According to my handy Pocket Reference book, radar frequency's are supposed to be between 1300-1600Mhz.
Does anybody have any notes, comments or useful information that they'd like to add?
Oh, and for a quick rundown of how radar works, for those of you who don't know, check it out at <a href="http://www.howstuffworks.com/radar.htm" target="_blank">HowStuffWorks.com</a>

<small>[ July 19, 2002, 01:17 AM: Message edited by: Energy84 ]</small>

AmonDin
July 19th, 2002, 02:53 AM
From my limited knowledge of radar, I don't see how you could detect CARS at 1-2 miles, aircraft probably, but not cars, trees/houses and all that would get in the way.

Energy84
July 19th, 2002, 03:02 AM
As long as I can focus the beam properly, I can get clear lines of sight for over 10 miles where I live. And if I feel like doing some hiking, I know a spot where I can see for at least 15 miles.
And yes, I live on the prairies. :cool:

PYRO500
July 19th, 2002, 04:03 AM
I don't think you'll easily just create a radar gun, there is a fair amount of integrated electronics in them just related to transmitting and receving let alone counting the frequency shift in the pulsees.
look on this page for some downloads on electronic kit manuals, there is a microwave motion sensor and a radar gun kit, the first is the simples but if you look at the radar gun circuit you'll see what I mean.

pyromaniac_guy
July 19th, 2002, 07:07 AM
energy84... i'm a bit confused by where you say 'detect a car at a distance' do you mean that if you sight on a car at a distance, you want the device to be able to see a microwave reflection off of the car, or are you wanting to build an automated device to actually DETECT the presence of a car??? there is obviously a huge diffrence in difficulty between the two tasks...

Energy84
July 19th, 2002, 09:23 AM
For now, I just want to point the device at a car and have the device detect it and be able to tell distance/speed. A working system that will automatically detect any contacts will later be in the plans. A radar system of this type is basically just a radar gun that spins in circles. When it pics up a contact, it just appears as a blip on a screen. The position of the blip is determined by the position of the radar gun at the moment of contact.
In the near future however, I just want the device to be able to detect something like say, a wall and tell me how far away it is.
PYRO500, I figured that alot of the integrated electronics could be eliminated by using the BASIC Stamp 2p, but I could be wrong. I've never really seen a wiring diagram for this type of thing. It's my understanding, from <a href="http://www.geocities.com/CapeCanaveral/Hangar/8528/intro_e.html" target="_blank">this page</a> that frequency shifting is not used in regular radar but rather it's used where extremely high accuracy is required and a continuous wave is transmitted. This type of system is used alot in guided missles.
BTW, I think you forgot to put in the URL for the site that you are referring to.

PYRO500
July 19th, 2002, 10:29 AM
here's the link
<a href="http://www.ramseyelectronics.com/sitepages/hkdownloads.htm" target="_blank">http://www.ramseyelectronics.com/sitepages/hkdownloads.htm</a>

somewhere a while back I saw a circuit to detect motion with a microwave sensor attached to a basic stamp.
As far as speed sensing, that's were you need to detect dopplar shift of the reflecting radio waves.
If you need to just detect the proximity of the object you could possibly build an adjustable oscilator and use an osciliscope to detect the diffrence in reflected frequency's I dont think you'll be able to economically get all the parts for a high power multi killowatt pulsed radar but they do have gunn diode transmitter/recever pairs but I'm not sure of their speed in trnasmission and reception beacuse the data they are designed to send is slower than radar pulses.

Energy84
July 19th, 2002, 10:53 AM
The doppler shifting for speed determination problem does concern me. It would be very tricky to build I'm sure, but I've got another idea. What if I were to use simple physics. Instead of measuring the change in frequency, I would simply measure the change in range and determine speed from that. ie. the target is at a range of 152m at T1 and is detected again (T2) 0.5s later at a range of 151m. Simple math dictates that the target is travelling at 2 m/s. I don't see any problems with using this method over the doppler shifting method other than mabye more precise timing required.
Also, can doppler shifting be used to measure the speed of targets travelling parallel to the radar gun? I'm under the impression that it cannot, but mabye it can.

auzquad
July 21st, 2002, 10:52 AM
learn to spell

<small>[ July 22, 2002, 07:12 AM: Message edited by: Machiavelli ]</small>

mrloud
July 21st, 2002, 11:22 AM
147 Words in one sentence. We could have a new record here gentlmen.

Doppler shift and change[distance]/time readings will only tell you how fast an object it moving directly toward or away from you. If you also take into account the change[bearing to the object]/time you can work out its vector (velocity *and* direction).

Also, have a look at some marine based radar systems. They are pretty cheap (for a radar setup) and can do some funky stuff with regards to proximity alerts.

Have a look <a href="http://www.whitworths.com.au/" target="_blank">here</a> and run a search for "radar"