Monday, December 11, 2006

Because Mike Said So

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Fun: Gunnplexer Radar Components

So, what's available for radar components on the open market? Most radar guns (aka cheap hardware) is either in the 10GHz band or the 24GHz band. These high frequencies are also used by ham radio operators, so they sometimes try to use these as high bandwidth line of sight radio links.

So, where to get them?

IF you want new, expect to pay $500 to $1000 per node. Advanced Reciever is one that lets you know without requesting a quote.

How about used?

Well, depending on availability, you can assemble much of the parts you need from SHF Micro.

So, my friend Creuzer was wondering about interesting feedback effects versus police radar, so let's go over what you'd have to do. Police radar works purely on doppler effect. Gunnplexers use a pair of tuned diodes to produce a beat frequency from a continuous wave source, so speed is a simple conversion of output frequency to speed. Now, how do you play games with one?

If the police radar is "dumb" (common), the radar electronics will lock onto the most powerful signal. Because your return is FAR more powerful than his reflection, you should win this fight. Now, the tricky part. You'd have to take in his signal, determine the initial doppler shift from knowing your own speed, and then fire off the right frequency to add or subtract whatever you want to to that radar signal.

A "smart" radar system (does it even exist?) that looks for a specific strength return requires more time and investment. You'd have to apply something (like, say SHF's Eccosorb AN-73) that will reduce your radar profile. Of course, you also have to protect the usually expensive components, which would require a good dielectric (radar transparent) coating of plastic over the top. You might also need to apply a fine metal mesh to your windows to keep the RF from bouncing off your head and back to the gun (and then you can control the radiant direction more). Anyway,
you'd have to take a power measurement and try to radiate back a certain percent of that. This would also help with the "dumb" radar but it's far more expense than it's worth.

Sounds simple? Well, it might be, but there's an issue. Radar gunnplexers tend to "float" their tuning all over the place within a 3GHz band, and you usually only have 100MHz or so of available bandwidth. So, know your police radar bands and hope they have it tuned! Mind you, the old hardware worked at either X band (10.5 to 10.55GHz) or K Band (24.05 to 24.24GHz). Relatively more modern hardware runs somewhere between 34.2 and 35.2GHz. I've only found one reference to these, and it was from Japan and cost about $3000 per unit if my translation is right. 35GHz is becoming more common, though, I've seen a lot of miniature radar units (for UAVs) being built around hardware at this frequency.

And that is why I don't mind spilling this little tidbit. Unless your local police is using hardware from the 80's (they might be though!), you'll probably never be able to mess with their readings.

Tuesday, December 05, 2006

Fun Thoughts: Bad Drivers

I've read several traffic related stories lately, mostly about the new tailgate detecting laser system deployed in Airzona. Interesting, but I thought of a far more interesting result.

Everyone seems to have a cartop cargo pod these days. How about we spruce one up?

First, bolt on a few fiberglass Sidewinder lookalikes. I'd probably modify them so you can point one forward and one behind. Add cones to the engine are to both disguise the fake-ness and help with the aerodynamics.

Second, put a couple of windows in the front and rear. Behind these put a surplus 10GHz or 24GHz Gunnplexer and horn (the core waveguide of most police radars) and a 905nm IR laser with optics to provide a flat cone (police laser radar). This will let you light up someone's life if they're the speedy paranoid type or the annoying tailgater. This will have no effect on those who don't have radar detectors. I'd probably have to add in an LED system in the missile "nosecones" that would pulse in time with the radar pulse. Wonder what people would notice and believe from the movies...

Now, add a custom "I support direct application of traffic law" bumper sticker and some fake (or real) vehicle battle scars, and you'll have yourself a winner.

Not a cheap project. Figure $50-100 per emitter, plus the cargo carrier plus the missiles and mounts. You'll probably end up spending $1000 on this toy in the end.

A lot of space will still be available. What to do with it?

Careful design would allow you to place an automotive PC plus a bunch of sensors up top. Hook up a lot of cameras and you could provide a 360 degree tour (plus traffic stops by curious cops!). You could also run an algorithm to track speeders and get actual speed from them (it'd take some additional circuitry on the gunnplexers). A dedicated computer controlled pan-tilt-zoom camera turret would let you get a REAL good photo of them, too. GPS would be an obvious addition, too.

Now, silly and probably (highly) illegal stuff. Drill out and place LOTS of RGB LEDs in the exterior. Almost invisible when off, you could give yourself whatever lights you'd want depending on the control program. Keep the top clear and put a plastic bubble on top with a fake (or real) radar antenna spinning in it. THAT would get some attention. Maybe you could claim it's a weather radar? I know some people would actually want the missiles on the side to shoot, but I cannot condone that, nor having a mine dropper in the back to bomb that tailgater with grenades/caltrops/deer carcasses.