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#### steamer

Jan 1, 1970
0
--Lotsa links for police radar but I need a 'real' system that can
image objects over a range of several hundred feet and present this info on
a display. Has anyone seen kits/plans for something like this? The cheapest
deep...

$2k sounds like a bargain. Graham S #### steamer Jan 1, 1970 0 Don Bowey said: As I recall, you posted this elsewhere and got many responses. --None really useful Do it at least a bit better this time, by posting exactly WHAT the display device should be, how should the echo be presented on the display, an idea of what resolution is wanted, the physical constraints such as weight size, over what range of azimuth must it work, any primary power constraints? You say "RADAR, but do you also wish to consider ultrasonic? Do you have the ability to read and construct from a schematic without requiring Heathkit type guidance? --Yes, dear.. Shooting in the dark at the moment because it's just an idea at present but I suppose ideal output would be to a laptop computer display. The problem is to image pedestrians, bicyclists and other vehicles within a range of, say, 400ft, that may stray across my route, so figure a cone of view of maybe 45 degrees either side of centerline. Resolution: if I can see a pedestrian as any sort of blob on the display that's good enough. Weight isn't an issue as it'll be mounted on a vehicle; i.e. a hundred pounds of stuff is acceptable. Power would come from a 12-v car battery or I could use a 2kw genny. Ultrasonic might be doable but again I haven't got a clue, which is why I'm asking questions! Yes, I could build from schematics; I'm a machinist by trade so I can also fab most anything in the way of mechanisms needed for the project. The goal is to come up with something that could be released into the wild so that anyone in this predicament who desired such a system could build their own. What have I left out? S #### steamer Jan 1, 1970 0 Michael Kennedy said: I agree.. You will usually find if something costs$100 at the store
allready built, it will cost you that to build it yourself plus the labor.
Labor I can discount; what parts are needed? That's the main
question.. Being a machinist I can fab a lot of stuff from scratch, but the
electronics end of things has me baffled.

S

#### steamer

Jan 1, 1970
0
--Following up my own query. Made a trip down to HSC and talked to
the gang. The major problem with radar seems to be a legal one, as it is,
basically a high-powered transmitter which requires licenses I don't have to
operate. So plan B seems to be using other portions of the spectrum. Various
ideas put forth included:
-Sonar which, although intended for water, can be made to work at
ultrasonic frequencies in air.
-FLIR seems to be a winner as there is hardware available surplus.
Apparently Cadillac offered a FLIR, complete with a HUD (for imaging in rain
and fog) for two model years so maybe I can get lucky at a good sized
junkyard.
-One wild idea was LIDAR but I wouldn't have a clue where to go with
that one.
Thanks to those of you who offered *useful* info...

E

#### Eeyore

Jan 1, 1970
0
steamer said:
Labor I can discount; what parts are needed? That's the main
question.. Being a machinist I can fab a lot of stuff from scratch, but the
electronics end of things has me baffled.

Frankly I doubt you can even source the required magnetron as a 'hobby' item. Do
you plan to make your own radar dish too ?

Graham

E

#### Eeyore

Jan 1, 1970
0
Stephen J. Rush said:
As he said in a later post, the real problem is the licenses you need to
run a sufficiently powerful transmitter. The cheapest microwave oven has
a 2.4-GHz magnetron much more powerful than you'd need for a short-range

I have my doubts that a microwave oven magnetron is suitable for providing the very
short pulses required for radar. Talking of which, 'the modulator' that pulses the
magnetron supply will be another very difficult design.

Graham

B

Jan 1, 1970
0
Steamer, I think your question goes beyond the current state of the
art - at any price.

RADAR needs to be scanned to build up an image (linear image with a
circling antenna or 3D image with a more complicated 2D scanning
antenna, or with an electronically steerable antenna array). None of
these are labor intensive devices (unless you can machine a small
antenna with fast 2D scanning abilities). You will eventually hit the
need for lots of electronics and computing power.

As an aside, I think it was an engineer at Lockheed that bolted a
bunch of TV antennas to an outside wall here in Gaithersburg MD, about
10 years ago and processed the signals to generate radar like images
from aircraft and other items in the area. TV stations and Radio
stations put out hundreds of kilowatts from stationary antennas, and
that RF signal bouces off of remote objects and comes back to the
passive listener.

-low frequencies/long wavelengths mean large antennas - Lockheed had
an outside wall decorated in antennas.
-some TV transmitters might go up to 600 MHz, so smaller antennas are
possible. Cell phones go from 875 MHz up to about 2 GHz.
-your antenna might be an array of small antennas but then you have to
electronically switch, amplify, receive and process multiple streams
of signals
-processing each signal to detect fractional differences in arrival
time which would then indicate direction of signal (in 3D) is compute
intensive. I.e. you are trading receiver simplicity -- passive
antennas -- for computational effort (this is why radar dishes swivel
- they assume they are only looking at the single transmitter source
in one direction, and distance is determined by the time it takes for
the signal to reflect back to the antenna)
-You cannot generally detect living things with RADAR. The reflected
energy is going to be small, and you will need more dynamic range
(small reflection and hence more processing power or larger antennas)
to identify these living things. (Maybe flocks of birds at airports
are one of these cases where living things are detected)

The new terahertz radars are interesting, in that the wavelengths are
so small that at least in theory you could fit an entire antenna array
in a handheld device, but that's in the far future.

Cheers

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