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Radar Expert Explains How To Cheaply Add Radar To Your Own Hardware Projects

Soulskill posted about 10 months ago | from the for-tracking-your-personal-airfleet dept.

Hardware Hacking 69

szczys writes "Gregory Charvat has been playing with and teaching others about entry-level radar concepts for a long time. Now he's sat down and explained how you can do it yourself inexpensively. He says, 'One enabling technology for Radar was the cathode ray tube (CRT), which facilitated a method of measuring the time delay between transmitted and received waveforms. ... Today, rather than using a CRT we can use high-speed digitizers. This offers the obvious advantage of applying signal processing to acquired data so that only moving targets are detected, tracking can be achieved, imaging, and a multitude of other modes. But for hobbyist and consumer projects we do not need this much power, range, and can not afford the cost. We need the ability to sense like a long range radar (detecting only moving targets, imaging, Doppler, signatures, etc) but at short ranges and at low costs.' Charvat then proceeds to walk through several options for the amatuer hardware hacker."

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yah! (0)

Anonymous Coward | about 10 months ago | (#46340055)

Become the Radar Secret Service!

WITH RADAR!

My interest (0)

Anonymous Coward | about 10 months ago | (#46340083)

I would like to be able to jam police radar guns with an overpowering signal.

Re:My interest (4, Interesting)

Anrego (830717) | about 10 months ago | (#46340185)

Dunno about where you live, but around here, police use LIDAR which is much more difficult to deal with for the would be detector/jammer.

LIDAR is pretty much impossible to detect until it's pointing right at you, at which point the best you can do is try to jam it long enough to slow down (which is pretty damn obvious when the cops LIDAR gun goes nuts as soon as he points it at your car).

Re:My interest (2)

camperdave (969942) | about 10 months ago | (#46340461)

Dunno about where you live, but around here, police use LIDAR ...

THAT's why I covered my ride in black velvet.

Re:My interest (0)

Anonymous Coward | about 10 months ago | (#46340875)

When using LIDAR, you typically aim for the head lights which are pretty reflective. Unless you have a car from back when pop-up headlights were popular.

Re:My interest (0)

Anonymous Coward | about 10 months ago | (#46341283)

Actually the best target is the license plate. The "paint" on a license plate is essentially a bunch of corner reflectors [wikipedia.org] which practically guarantees the laser will be reflected directly back at the lidar gun even though the car is moving and the angles are constantly changing.

I'm surprised no one has come up with a plate cover that is (only) reflective in the IR spectrum that LIDAR operates but reflects up into the sky instead of back at the LIDAR gun.

Re:My interest (4, Interesting)

morethanapapercert (749527) | about 10 months ago | (#46341521)

There are several companies which market license plate covers designed to obscure your plate when targeted by certain technologies. Polarized covers to defeat roadside speed cameras, prismatic covers to defeat overhead cameras from toll roads and so on.

Problem is; most places in North America and I imagine Europe as well, already have laws on the books covering illegible or obscured registration tags and these covers often fall on the wrong side of the law. Personally, I'd rather get the speeding ticket than a missing/illegible plate ticket and would really really like to avoid any possible "obstruction of a police officer in the performance of his duties" charge.

Something else to consider; based on what seems to be the growing trend in the US: Do you want to get a speeding ticket which usually isn't a criminal act and only nets you a fine Or do you want to use a device whose (arguably) sole purpose is to break the law with impunity, leading to your car being declared as property used in the commission of a crime and confiscated? (while you get beaten half to death and charged with resisting arrest) If you speed, you are only in violation when you speed, but if you put a contraband plate cover on, you are in violation just parked on the street

Re:My interest (0)

Anonymous Coward | about 10 months ago | (#46343509)

Those license plate cover tricks?
They don't work. Mythbusters tried a bunch of them. Nothing worked even remotely as well as any potential buyer might hope.

Might as well drive through a bunch of muddy puddles. Cheaper, and you can say "Sorry officer I didn't realize. I'll go wash it off as soon as I get home." Who knows, it might even work too.

Re:My interest (1)

Anonymous Coward | about 10 months ago | (#46343567)

Might as well drive through a bunch of muddy puddles. Cheaper, and you can say "Sorry officer I didn't realize. I'll go wash it off as soon as I get home." Who knows, it might even work too.

SHHH! It works only too well, my friend, especially in rural areas on a 4x4 ...

Re:My interest (0)

Anonymous Coward | about 10 months ago | (#46344159)

There are several companies which market license plate covers designed to obscure your plate when targeted by certain technologies. Polarized covers to defeat roadside speed cameras, prismatic covers to defeat overhead cameras from toll roads and so on.

It is sad that you got modded +5 informative for that since none of those license plate covers address LIDAR - they are all about cameras. I was fully aware of those sorts of covers when I wrote the previous post. I considered mentioning them just to stop someone like you from coming along and spouting off about them, but I was hoping slashdot's group intelligence was smarter than that.

Something else to consider; based on what seems to be the growing trend in the US: Do you want to get a speeding ticket which usually isn't a criminal act and only nets you a fine Or do you want to use a device whose (arguably) sole purpose is to break the law with impunity, leading to your car being declared as property used in the commission of a crime and confiscated?

Do you see the inherent contradiction in what you wrote? If it isn't a criminal act in the first place then it isn't the commission of a crime.

Re:My interest (1)

morethanapapercert (749527) | about 10 months ago | (#46347931)

I said "Polarized covers...prismatic covers...and so on" I did not explicitly say covers to defeat LIDAR I'll grant you. I did, however, implicitly include them in the "...and so on" part of my statement. There are companies which advertise sprays and covers intended to absorb or scatter the near IR wavelength laser light police LIDAR systems use.

Speeding isn't the crime I was referring to, since most places consider most traffic offences to be a civil, not criminal offence. However, use of a device or substance to deliberately obscure your licence plate may or may not be part of the traffic code where you live, but rather covered by the criminal code. If use of a cover plate is considered a criminal act where you live, then the car is being used in the commission of a criminal act even when it's safely parked in your driveway. Having a plate obscured on a dirty vehicle by mud or snow is plausibly neglect, there's no clear proof of intent to evade the law. Thus; most police officers will give you a warning or a "fix-it ticket". But purchasing and installing a device whose sole advertised purpose is to evade detection by police as you break traffic laws inherently displays intent to do exactly that.

Please note that I also said "...in the US". There have been numerous news stories about law abiding people being pulled over for no more reason than having a nice car with out of state plates, having their vehicles searched and cash confiscated as "proceeds of crime" even when there is NO other evidence of any crime. People who then try to protest this get beaten up and charged with resisting arrest. My reasoning is this: If certain officers and/or certain police departments are using any pretext at all to pull someone over and search for things they can confiscate to support their department financially, I certainly don't want to risk driving around with one of the license obscuring items on my car.

Re:My interest (1)

advocate_one (662832) | about 10 months ago | (#46345033)

Most cars round where I live don't bother cleaning their number plates... the chances of actually being picked up by a ploice road patrol that could be bothered to do the stop are pretty slim. And if they were picked up, they have a simple excuse which should not really be allowed to stand as by law, your vehicle is supposed to be roadworthy which includes having legible plates and you're supposed to check certain things daily.

Stationary (0)

Anonymous Coward | about 10 months ago | (#46341947)

But the cop has to be stationary to use LIDAR, which limits the places it can be deployed. Here in CA I slow down for those places. Also, my V1 will detect LIDAR backscatter from vehicles ahead. And my front plate is missing (please pull me over, if you can be bothered) so there is no good target to place the laser when I am approaching, so they have to setup (stationary, again) from the back just to find a flat spot on the car. In theory it works, in practice V1 beeps, I lift, and some tard next to me (soon to be ahead of me) eats the ticket. /shrug

Re:My interest (1)

mjwx (966435) | about 10 months ago | (#46352947)

Dunno about where you live, but around here, police use LIDAR ...

THAT's why I covered my ride in black velvet.

The fact he's also a pimp is entirely coincidental.

Re:My interest (1)

NapalmV (1934294) | about 10 months ago | (#46340865)

So those "kids directing laser pointers towards airplanes" could in reality be officers mishandling their LIDARs? And, BTW, if pointing lasers at pilots/drivers is such a serious thing, why are police officers allowed to do it?

Re:My interest (4, Informative)

Electricity Likes Me (1098643) | about 10 months ago | (#46341355)

Well for one thing it's a low intensity infrared beam which is eye-safe and invisible.

Re:My interest (2)

Anrego (830717) | about 10 months ago | (#46341411)

Kinda apples and grenades there..

The low intensity _invisible to the human eye_ light from a LIDAR gun would never make it anywhere near an airplane, and even if it did, being invisible and all, it wouldn't matter.

Additionally, they are usually of low enough intensity and/or in a non-eye-focusing wavelength to be completely safe to the human eye. YOu could literally stare right into one with no adverse effects.

Re:My interest (2, Funny)

davester666 (731373) | about 10 months ago | (#46341667)

they are trained professionals. that's why they also get to drive without seat belts, talk and text on cell phones while driving, and speed with their lights off.

Re:My interest (1)

AmiMoJo (196126) | about 10 months ago | (#46345161)

Some adaptive cruise control systems (e.g. Nissan's) and laser parking sensors are known to interfere with speed guns using LIDAR. They are legal because they are a safety device, not a jamming device, and the police equipment just happens to be incompatible. That band (~900nm) is license free, interference is expected.

Re:My interest (1)

azav (469988) | about 10 months ago | (#46346709)

I once knew a guy (20+ years ago) who had a microwave element mounted in front of his radiator, the radiator shielding him from the glorious waves. He had his radar detector wired to trigger the microwave when it detected a radar gun signal, effectively roasting the radar gun.

At least this is what he told me.

I think he did this after getting fed up with Connecticut State Troopers, their speed traps and unmarked Ford Tauruses and Jeeps pulling people over at 56 miles an hour. Setting my memory back to 20 - 30 years ago, I don't blame him one bit.

Re:My interest (0)

Anonymous Coward | about 10 months ago | (#46341125)

I would like to be able to jam police radar guns with an overpowering signal.

So you can enjoy a gigantic fine and/or jail time from the FCC instead of a mere traffic ticket? Brilliant. </sarcasm>

Re: My interest (1)

rickb928 (945187) | about 10 months ago | (#46350665)

A little more work with the jammer and the police will not easily figure out who it was, nor find the device.

I'm intrigued. Low power radar ain't that hard to defeat. Lidar isn't either, and you don't need flares.

Poking sticks in the NSA/DHS hornet nest (0, Funny)

Anonymous Coward | about 10 months ago | (#46340109)

I can see it now.

There you are innocently trying out your new homemade RADAR near the local airport. Your signals, as you bounce them off commercial airlines coming into land, are spotted quite easily by the tower and reported on to whomever controls security around the airport.

You hear the sound of the 777 you have your cantenna aimed at suddenly drowned out by the much louder sound of a military jet approaching, the twin snake of missile exhaust flashes for a split second from under the wings.....

News just in: Evil terrorist, planning to bomb a 777 and kill all passengers on board, killed by Air Force air to surface missile near JFK.

Re:Poking sticks in the NSA/DHS hornet nest (0)

Anonymous Coward | about 10 months ago | (#46340173)

News just in: Evil terrorist, planning to bomb a 777 and kill all passengers on board, killed by Air Force air to surface missile near JFK.

JFK, planning to bomb an evil terrorist, killed by VP now aboard Air Force One?

Re: Poking sticks in the NSA/DHS hornet nest (0)

Anonymous Coward | about 10 months ago | (#46341339)

I'll try this near MCI.

What's in car bumpers? (1)

Anonymous Coward | about 10 months ago | (#46340123)

What tech do auto makers use for the proximity detectors in car bumpers?

Seems like that'd be an inexpensive, short range detector, even if it's not radar.

Re:What's in car bumpers? (1)

jonwil (467024) | about 10 months ago | (#46340263)

I have a family member with a Ford Focus. This has reversing sensors that warn you if you are about to reverse into something.

Whatever tech those are using seems like it would be good to try out.

Re:What's in car bumpers? (1)

RabidReindeer (2625839) | about 10 months ago | (#46340439)

I have a family member with a Ford Focus. This has reversing sensors that warn you if you are about to reverse into something.

Whatever tech those are using seems like it would be good to try out.

At least "trickle down" works in automotive tech. First I learned about them was when I tried to back a rented Lincoln into a wall and the alert went off. Thankfully.

Now there's backup cameras in the new Honda Civic.

Re:What's in car bumpers? (4, Funny)

Opportunist (166417) | about 10 months ago | (#46341613)

Ffft, we had an audible proximity alarm in our car before it became fancy. When you heard the bumper crunch, you knew you went too far.

So it was very close proximity. So?

Re:What's in car bumpers? (1)

RabidReindeer (2625839) | about 10 months ago | (#46344779)

Ffft, we had an audible proximity alarm in our car before it became fancy. When you heard the bumper crunch, you knew you went too far.

So it was very close proximity. So?

I detected a Cadillac that way once, alas.

Re:What's in car bumpers? (3, Informative)

stox (131684) | about 10 months ago | (#46340283)

Utrasonic SONAR is used for parking proximity parking sensors.

Re:What's in car bumpers? (1)

khellendros1984 (792761) | about 10 months ago | (#46340403)

FTFA:

Additional impulse radar systems are being manufactured in quantity for automotive applications (blind spot detection, parking aids, etc), but details on these are not easy to find unless you directly engage the manufacturers. Manufacturers of automotive radar equipment include, Delphi, Continental, TRW, Bosch, Denso, and Autoliv.

Some vehicles may use sonar. The article claims that at least come manufacturers are using a form of radar.

Re:What's in car bumpers? (1)

_merlin (160982) | about 10 months ago | (#46343479)

Radar tends to be used for the collision avoidance features rather than the parking assistance stuff.

Re:What's in car bumpers? (0)

Anonymous Coward | about 10 months ago | (#46343675)

Sonar can be used for parking proximity parking sensors, amongst other range-finding technologies such as radar.

FTFY. Even the lowly BMW 325i has radar parking sensors. Sonar is a low-end solution, for the obvious reason of reliability (ambient noise is a problem and sonar systems have moving parts that wear out, and get dirt & dust stuck in them).

Re:What's in car bumpers? (1)

RabidReindeer (2625839) | about 10 months ago | (#46340407)

What tech do auto makers use for the proximity detectors in car bumpers?

Seems like that'd be an inexpensive, short range detector, even if it's not radar.

Ultrasonic. They were selling experimenter units at Radio Shack when I was in there last month. For general use, not specifically for automotive mounting. I think in retail, they're about $30.

probably ultrasonic. Lego, Radio Shack has it. (1)

raymorris (2726007) | about 10 months ago | (#46340767)

Those are probably ultrasound. Ultrasound distance sensors are available at Radio Shack and included in Lego Mindstorm kits.

Re:What's in car bumpers? (1)

anubi (640541) | about 10 months ago | (#46343079)

What tech do auto makers use for the proximity detectors in car bumpers?

How about these? [aliexpress.com]

Re:What's in car bumpers? (3, Insightful)

drkim (1559875) | about 10 months ago | (#46343631)

What tech do auto makers use for the proximity detectors in car bumpers?

Ultrasonics. Just like the old Polaroid Camera auto-focus.

http://www.northerntool.com/sh... [northerntool.com]

Easier now, but not new to ham radio guys (4, Interesting)

mpoulton (689851) | about 10 months ago | (#46340249)

The new single-chip radar solutions and FMCW radar modules are definitely much easier to use and more capable than what was available just a few years ago, but DIY radar is nothing new. Amateur radio operators have been playing with radar guns and door sensors for decades, and doing some pretty interesting things with them. I remember reading photocopies of articles from QST from the 1970's that explained how to hack door sensors to make speed detectors, as well as using them for long-distance voice and video transmission with parabolic reflectors. People have also been playing with marine radar, which is considerably more expensive but still affordable for a dedicated experimenter.

Re:Easier now, but not new to ham radio guys (0)

Anonymous Coward | about 10 months ago | (#46341003)

There are many real world uses for radar beyond communications and military applications. There is a small but specialized industry of factory and process sensors using ultrasonics and radar to measure material levels in tanks and vessels with high pressures and temperatures.

Specific frequency bands and maximum power levels for radar are tightly regulated by the FCC and others so be design your oscillators carefully.

An non-DIY example using 78 GHz FMCW and lens antennas:

http://www.automation.siemens.... [siemens.com]

Re:Easier now, but not new to ham radio guys (1)

anubi (640541) | about 10 months ago | (#46343403)

Here are the little doppler 10GHz radar toys I have been playing around with. I had been playing around with a boxful of old radar detector returns - being I had a lot of horns, I put the Gunn diode at the focal point of one and aimed it out, then watched for multipath doppler at the other receiving horns. My intent was to triangulate from several receivers and from that deduce the location of anything moving in the field. Never got that one to work the way I wanted it to... and it drew too much power to boot.

Anyway, I have been lately playing around with these. [aliexpress.com] Cheap. You get a frequency out in the hertz region, with its amplitude and frequency representing the size and speed of the object being sensed. This thing is from what I can tell is the same technology used in supermarket door sensors. Personally, I like hooking them up to variable frequency audio oscillators so if I get woke up in the middle of the night and I think something's in the house... just keep real still and anything moving at all will show up as variances in pitch - and you know right quick if something is moving around anywhere in the house.

Hammer chewer? (0)

Anonymous Coward | about 10 months ago | (#46340265)

"amatuer hardware hacker.""
^^^^^^^^^^^

FFS does Beta not have a spell checker?

Silly Acronyms (2, Funny)

WiiVault (1039946) | about 10 months ago | (#46340279)

What is a CRT? It it pronounced like Kurt, or CeeeArrrrrTeeee? Do they come with any cool apps? I do like the idea of my own ray tube though. Sounds pretty up and coming. Anybody know of any upcoming IPOs investing in this tech?

Re:Silly Acronyms (1)

tjb6 (3421769) | about 10 months ago | (#46340423)

It's like a CRO, but considered more general purpose, more entertaining, but less useful to the tech head.
Which is funny, as the average CRT just hums gently, while a CROw is pretty noises (Vaaark!)

Re: Silly Acronyms (0)

Anonymous Coward | about 10 months ago | (#46340561)

CroooooooooooOOOOOOOOOOOW! (that's one O)

Re:Silly Acronyms (1)

MildlyTangy (3408549) | about 10 months ago | (#46340469)

What is a CRT? It it pronounced like Kurt, or CeeeArrrrrTeeee? Do they come with any cool apps? I do like the idea of my own ray tube though. Sounds pretty up and coming. Anybody know of any upcoming IPOs investing in this tech?

If only there was a way a person could use Google to do a quick search to find out what a CRT is. If that were possible, then you wouldnt even need to spend all that time and effort to post a question on a Slashdot article in the vain hope somebody will tell you the answer.

If only there was a way to use Google, everybodys life would be so much easier.

Maybe some day a smart person will figure out a way to do this, but unfortunately it looks like you will have to wait for your answer. Sucks to be you.

Re:Silly Acronyms (0)

Anonymous Coward | about 10 months ago | (#46340681)

http://lmgtfy.com/?q=How+do+you+say+CRT%3F

Re:Silly Acronyms (0)

Anonymous Coward | about 10 months ago | (#46340797)

I'm pretty sure it was supposed to be a joke about how fast technology changes.

Re:Silly Acronyms (1)

WiiVault (1039946) | about 10 months ago | (#46346291)

Bingo! We have a winner.

Re: Silly Acronyms (1)

rickb928 (945187) | about 10 months ago | (#46350729)

Whoosh.

Re:Silly Acronyms (2)

Mr Z (6791) | about 10 months ago | (#46342671)

It refers to the C Run Time, aka. the C standard library. Back in the day, only C programmers were able to operate radar. Nowadays, they can monitor radar with jQuery and node.js.

Re: Silly Acronyms (0)

Anonymous Coward | about 10 months ago | (#46342977)

That's only becase C programmers always have coffee when they watch radar. Everyone knows that.

Almost there (1)

Tablizer (95088) | about 10 months ago | (#46340419)

Now if I can only find a shark...

Hacker? (0)

Dan Askme (2895283) | about 10 months ago | (#46340623)

amatuer hardware hacker
http://hackaday.com/ [hackaday.com]

Since when has Hardware Engineering being incorrectly classed as "hacker"?

I cant stand it when the word "hack" is used by everyone, incorrectly, for everything. Its just insulting to their own intelligence.
I hacked my cup of coffee today, i added a sweetener instead of sugar, omg!......

Jargon file: hacker meant radio hardware before CS (1)

raymorris (2726007) | about 10 months ago | (#46340843)

According the the Jargon File, the definitive dictionary of hacker terminology, the word "hacker" ORIGINALLY referred to radio experimenters who did things like make or modify radar units. Later, it was used to describe people doing similar hacks with computer systems.

Re:Jargon file: hacker meant radio hardware before (0)

Dan Askme (2895283) | about 10 months ago | (#46340927)

According the the Jargon File, the definitive dictionary of hacker terminology, the word "hacker" ORIGINALLY referred to radio experimenters who did things like make or modify radar units. Later, it was used to describe people doing similar hacks with computer systems.

Google has the correct definition.

hacker
hak/Submit

noun
noun: hacker; plural noun: hackers

1. a person who uses computers to gain unauthorized access to data.
informal
an enthusiastic and skilful computer programmer or user.

2. a person or thing that hacks or cuts roughly.

Re:Jargon file: hacker meant radio hardware before (1)

Ozoner (1406169) | about 10 months ago | (#46342513)

Well, It's wrong. A Hacker originally was anybody who built or modified electronics
(not just Radar).

I know, I was there.........

any early citations in your attic (or PDP)? (1)

raymorris (2726007) | about 10 months ago | (#46342553)

I don't suppose you have any early text using the term? The jargon file itself is pretty old now. If you have a clear use of the term much earlier it could be of historical interest to many people.

Ozoner, would you say "I knew the original hacker. The original hacker was a friend of mine. Dan, you're no original hacker"? :)

Re:any early citations in your attic (or PDP)? (1)

Dan Askme (2895283) | about 10 months ago | (#46344395)

I don't suppose you have any early text using the term? The jargon file itself is pretty old now. If you have a clear use of the term much earlier it could be of historical interest to many people.

Seems referencing some proof to backup claims on Slashdot isnt the way to go anymore.

Just look at my Google reference with 0 scores... :)

jargon file predates Goog by 20 years, is a source (1)

raymorris (2726007) | about 10 months ago | (#46344775)

Google finds content, it doesn't create content. Google found that definition somewhere, and we don't know where. Therefore citing Google is precisely the same thing as saying "some random web site says ..."

Additionally, jargon file is maybe 20-25 years older than Google, so for the _original_ meaning of a term jargon file trumps Google by a long shot.

Re:jargon file predates Goog by 20 years, is a sou (1)

Dan Askme (2895283) | about 10 months ago | (#46355989)

Google finds content, it doesn't create content. Google found that definition somewhere, and we don't know where. Therefore citing Google is precisely the same thing as saying "some random web site says ..."

Additionally, jargon file is maybe 20-25 years older than Google, so for the _original_ meaning of a term jargon file trumps Google by a long shot.

If Google cant find your "Jargon File", how the hell will i ever find it? lol

Please, for the love of God, link this "Jargon File" and prove me wrong :)

any of the first 15 Google results (1)

raymorris (2726007) | about 10 months ago | (#46363877)

When I search, the first 15 Google results for Jargon file are correct. The third one is the entry for "hacker", which is interesting. In case your Google is broken, the primary copy is http://www.carb.org/jargon/ [carb.org]

Have you seen the xkcd about diet Coke and Mentos? It kind of expresses how I feel right now, getting the honor of introducing you to a classic bit of geekdom. Sergey and Larry almost surely would have read the Jargon File when they were in college.

typo: catb.org, ESR's page (1)

raymorris (2726007) | about 10 months ago | (#46363969)

My post has a typo. That should be http://www.catb.org/jargon/ [catb.org]

Catb is Eric S. Raymond's page. If you're not familiar with ESR yet, he's pretty awesome. I highly recommend two of his essays, "How to Ask Questions the Smart Way" and "the Cathedral and the Bazaar".

Re:typo: catb.org, ESR's page (1)

Dan Askme (2895283) | about 10 months ago | (#46375961)

My post has a typo. That should be http://www.catb.org/jargon/ [catb.org]

Catb is Eric S. Raymond's page. If you're not familiar with ESR yet, he's pretty awesome. I highly recommend two of his essays, "How to Ask Questions the Smart Way" and "the Cathedral and the Bazaar".

Thanks for the sharing the link, will have a good read :)

Re:Hacker? (0)

Anonymous Coward | about 10 months ago | (#46340979)

I cant stand it when the word "hack" is used by everyone, incorrectly, for everything. Its just insulting to their own intelligence.

Yeah, why don't people understand that hacking can only involve playing with trains. No trains? Not a hacker.

Re:Hacker? (0)

Anonymous Coward | about 10 months ago | (#46341385)

I think "3D printing" is the same thing. "I 3D printed my car today" = cup holder.

Question about "Doppler Dilemma" (1)

Miamicanes (730264) | about 10 months ago | (#46342661)

For anybody who knows... could a radar system partly or completely side-step the Doppler Dilemma ( http://en.wikipedia.org/wiki/W... [wikipedia.org] ) by doing DSS or FHSS and cycling through a sequence of different carrier frequencies from pulse to pulse?

Re:Question about "Doppler Dilemma" (1)

tuxicle (996538) | about 10 months ago | (#46345739)

It's easier than that - use two blocks of different repetition frequencies (which gives two different Nyquist velocities), get two velocity readings. Some basic number theory will get you the right answer.

Using two different carriers is going to alter the Nyquist velocity by such a small amount that it's not worth doing. Unless the carriers are very widely separated (go from say, 2.7 GHz to 5.8 GHz) but this requires a wideband (and necessarily low gain) antenna.

That's not to say that FHSS is not used by weather radar - its purpose is to improve the quality of measurements by increasing the number of statistically independent samples that get averaged together.

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