Car Talk BO-o-O-GUS Science!

[Sundog]

This is the opportunity of a lifetime to hear Tom admit on the air that he's an ignoramus, if you've ever wanted to hear that, and we can help.

First of all, if you don't know what Car Talk is, it's an NPR show about car repair hosted by two fairly smart guys, Tom and Ray Marriazi (sp?). Funny show, the guys are very entertaining.

This week a caller asked why aiming his remote unlocking device at his chin let him get better range. Ray expressed an opinion that the "signals" were bouncing off his face and dispersing, giving a better range. (This part DOES seem bogus to me; would your face reflect radio waves?)

Ray explained his answer by comparing it to a TV remote. He said that sometimes your remote will work better if you aim it at the wall behind you than if you aim it right at the TV, because the wall disperses the "signals", and the TV only responds over a limited angle.

Which is, of course, precisely correct. The IR transmitter has a lens on the end of it intended to restrict the IR beam to a very small angle, to minimize loss. This is why you have to point the remote RIGHT AT the TV. The receptor, on the other hand, is a simple IR detector. If you point the remote at a white wall behind you, a halfway powerful remote will shine its beam on the wall, which will then bounce back to the IR receptor on the TV.

(If you use a video camera that works in very low light you can SEE this happening; TV remote beams are visible to the camera. It looks like you are shining a penlight on a white wall.)

Tom reacted as if this was the most BO-o-O-GUS thing he had ever heard. He laughed so hard he could hardly get words out. In fact, he laughed right through the credits, all the way to the end of the show.

(And yes, he was clearly laughing at the TV remote part, not its application to the caller's problem, which may very well be bogus.)

Ray appealed to people, especially people with "credentials", to log on to their BBS at cars.com and vindicate him. I think it would be great if some of our local brains got involved and helped. I have no credentials other than as a registered smartass.

Anyone interested? It might get your name on national radio.

 

[EvilYeti]

Uh, TV remotes use infrared transmission, whilst car remotes use radio waves. Infrared waves are absorbed or reflected by most things that would absorb or reflect regular light. Radio waves behave much differently.

My theory regarding the car remote is that it has more to do with the position and height of the remote vs. the proximity to a human skull. Tiny transmitters such as these don't have much in the way of an antenna, so their dispersion patterns are highly irregular. It's highly likely that the particular angle of the transmitter when held against the chin just happens to direct more radio energy towards the car than otherwise. The only way to prove it would be to hook up a voltmeter to the antenna on the car that receives the signal from the remote. That way you could easily measure the signal strength.

 

[Sundog]

Uh, TV remotes use infrared transmission, whilst car remotes use radio waves.

I thought I made that clear, sorry.

I agree, the height is almost certainly the reason for the range increase, especially in a parking lot full of metal.

Any opinion on the central question?

 

[EvilYeti]

Any opinion on the central question?

I'm not sure what it is. Assuming its whether a human head could reflect radio waves, I would have to give that an enthusiastic "depends"! Humans are mostly water and react as such when encountering radiation, which usually means its either gets absorbed, passes through, or a little bit of both. But if the guy had alot of metal dental work, or a metal plate in his head, who knows?

Its possible this could be tested, as I said, with a voltmeter on the antenna (thats how we test signal strength) but the transmission might be too short and low power to be measured with a typical meter.

 

[Sundog]

Naah, I mean on the REALLY important question: Can we nail Tom!

 

[patnray]

It is true that the TV remote uses a narrow IR beam. I'm not sure about the dispersion off a white wall part. First, the reciever does have a limited angle at which it can sense the beam. This angle is much wider than the narrow beam angle, but much less than 180 degrees. When I am in a location where I don't have a direct path to the TV sensor I bounce the remote off mirrors, picture frames, or windows. The beam bounces off a reflective surface to the reciever at a better angle to be sensed. Our off-white stucco walls do not work very well, but there are plenty of reflective objects in the room.

I suspect, though, that the laughter may have been because of the inappropriate analogy between a radio transmitter and an infra-red transmitter...

Salt water does reflect radio waves. Cells are mostly salt water. But the weak reflection off an irregular shape would disperse the signal, not concentrate it...

 

[EvilYeti]

Naah, I mean on the REALLY important question: Can we nail Tom!

Probably not, though I'm not sure what he exactly is laughing about. If its TV remotes, then he is wrong. That is common sense for the reasons you explained; one is using the wall to change the radiation pattern from a directed, high-power beam to a diffuse, low-powered one. This only works better close to the set, however. As you move farther back the beam will diffuse naturally and reflecting it might not have enough power to register on the sensor.

Car remotes are a totally different animal for two reasons; one, they use radio waves, as already mentioned and two, they do not have a directional dispersion pattern. It would be possible to make the pattern a little more directional by placing the transmitter inside a Yagi antenna, but a human would probably not work.

It is POSSIBLE, maybe, that the individual was acting as a shield and preventing destructive interference from nearby reflective surfaces. If that was the case he would not be "boosting" the signal, merely removing some interference that was preventing the sensor from properly detecting it.

 

[Sundog]

I suspect, though, that the laughter may have been because of the inappropriate analogy between a radio transmitter and an infra-red transmitter...

You would think so, since that part probably IS bogus, and from the way I described it. But I'm pretty sure the laughter was all directed at the TV remote part; Tom objected to several specific parts of it then collapsed in laughter.

That's the big question, of course.

 

[TexasBEAST]

Maybe the guy with the remote was wearing one of those aluminum foil anti-brainscan hats?

 

[Cain]

Naah, I mean on the REALLY important question: Can we nail Tom!

Not sure. I think this only makes sense to homosexuals and hitmen. I listened to that show on NPR a couple weeks ago (I think Saturday afternoon). Those guys are annoying.

 

[Sundog]

Not sure. I think this only makes sense to homosexuals and hitmen. I listened to that show on NPR a couple weeks ago (I think Saturday afternoon). Those guys are annoying.

Just curious, why the gratuitous gay and Italian bashing?

Just wanted to see if you had any excuse before you go on my ignore list.

 

[TillEulenspiegel]

You would think so, since that part probably IS bogus, and from the way I described it. But I'm pretty sure the laughter was all directed at the TV remote part; Tom objected to several specific parts of it then collapsed in laughter.

That's the big question, of course.

The answer was approximated in some previous posts.
The difference between to two is that the TV remote is IR. and the door fob is an RF device.

The reason that you can bounce the TV remote signal is because the output altho IR , it IS light and will bounce off any light colored wall ( shiny enamel works best) , mirrors , basically any reflective surface, after all IR is just light, we just can't see it. The light defuses off the uneven surface and bounces back to the receiver. Even though the light level is lower it's spread over a larger surface and is "seen" by the IR detector in the TV.

The door remote is a miniature RF transmitter in the low Mhz range ( altho some hi freq and spread spectrum devices are available). It's antenna is normally a piece of plastic tape with a spiral of conductive material ( copper) that is stuck to the back of the transmitter or the printed circuit board that the circuit is mounted on. The transmissive pattern with this configuration projects an RF field that tends to be bidirectional in the shape of an 8 in aspect to the two larger sides ,where the two lobes of greatest field strength is at 0 and 180 degrees. The RF energy passes easily through human flesh but will bounce off any metal around the transmitter I.E. other cars, metal reinforcing rods in the concrete , corner guards in the garage , even off a necklass and (depending on the freq. ) the concrete. The reason for the perceived increase in functionality when he holds it up is he is "pointing" the antenna with the pattern for the greatest transmissive energy towards the car ( and probably enjoys a straight line of site to the car antenna because of his height to boot ).

 

[EdipisReks]

Maybe the guy with the remote was wearing one of those aluminum foil anti-brainscan hats?

sorry to go off topic here, but those tin foil hats are funny. if there was anything actually scanning someone's brain, those tin foil caps would actually improve the reception, since the edge of the aluminum foil would act like an antenna.

 

[SFB]

sorry to go off topic here, but those tin foil hats are funny. if there was anything actually scanning someone's brain, those tin foil caps would actually improve the reception, since the edge of the aluminum foil would act like an antenna.

Sorry to go further off topic here:

Umm, I don't think so; would it not depend on distance, frequency, and RF power?

The idea behind the foil hats seems to be that one protects one's brain from ambient RF energy that would otherwise penetrate in order to ???? (I really dunno, monitor thought somehow?) It's all pretty wacky.

I am not at all knowledgeable on this and hope for clarification. It just seems to me foil would reflect ambient RF. But what about IR? Now there's something .... (perhaps) for the whacked woo-woos (and on this level they are truly whacked - PM me, I'll send ya links).

AND at what level would foil be defeated by higher levels of RF frequency and/or power? Or distance for that matter? So on this level I think you may have something. That is, if with increased power, frequency, or distance foil may be overcome. Surely at some distance, power, and frequency, but what??? I guess a definition of "ambient" is in order.

I solicit anyone who may know better to comment........

 

[Luke T.]

It seems to me that by bouncing the IR remote signal off a wall or other reflective surface just increases the distance the signal has to travel and therefore results in a wider spread pattern of that signal. This would make it more likely to be picked up by the sensor on your TV.

 

[Brian the Snail]

Just curious, why the gratuitous gay and Italian bashing?

Just wanted to see if you had any excuse before you go on my ignore list.

I think Cain was making a joke regarding your question "can we nail Tom?" based on the ambiguity of the term "nail", which can also mean "to engage in sexual intercourse with someone" or "to kill someone." Although not the funniest comment in the world, my own personal feeling is that it does not constitute "bashing" of the particular groups of people you mention.

I'm actually more interested to learn why you feel that the word "hitman" constitutes bashing of Italians. Do you think that the two are synomynous?

 

[Sundog]

I'm actually more interested to learn why you feel that the word "hitman" constitutes bashing of Italians. Do you think that the two are synomynous?

I don't understand the question. These are just two very likeable, very Italian guys on the show, he makes a comment about only hitmen understanding it, I object to it, and somehow this indicates prejudice on my part?

It's off-topic anyway, let's not let him sidetrack the discussion.

 

[TillEulenspiegel]

EdipisReks:


"sorry to go off topic here, but those tin foil hats are funny. if there was anything actually scanning someone's brain, those tin foil caps would actually improve the reception, since the edge of the aluminum foil would act like an antenna"

Thats just plain silly. An antenna is normally tuned and can both receive and transmit energies in the tuned band best, with a signal loss that resembles a bell curve with the optimum efficiency being in center of the tuned band.(there are variants that have application in real life utilizing fractions aka harmonics of the fundamental Fq but that would only confuse the issue.) As far as the human brain is concerned it generates signals at about 60 Hz.. with a relative measurable strength of micro volts. So... a metal hat would wouldn't couple these weak signals and in fact would act as a Faraday shield to decrease the availability of data. The interference from all the devices that generate electrical fields TVs, fluorescent lights , neon signs..ect.,would cancel out any effective specific targeting. There are other reasons that a schema like this wouldn't work but the basics here are reason enough to dismiss the effort =)



You could tho place a wire from the hat to a tooth that has a cavity in the vicinity of a strong signal generator ( AM radio station, mostly in Spanish or talk radio and hear stuff ). This happens all the time in relation to fillings or metal plates in the cranium, so as a receiver the hat will work somewhat ( hell the first radios used a cat's whisker as a signal detector.) as a device that transmits recognizable , useful data it is a flop.

SFB: "AND at what level would foil be defeated by higher levels of RF frequency and/or power?"

As far as raw power levels to over come the shielding effect, it would cook the brain ( it would also have to be specifically targeted or else all the humans in the vicinity as well as sensitive machinery would be fried.).

Another consideration is the fact that the brain interprets and initiate information in a 3 dimensional matrix, the brain itself ( kind of like a holograph) it is not linear like a newspaper or even speech, to gather this signal and couple it to a transmitter would take machinery that would make a Cray Supercomputer look like a stick.

Much more could be said about the non-feasibility of this silly line but suffice to say it is roughly equivalent to the proclamation that vampires can be kept at bay by the use of garlic cloves.

 

[SFB]

EdipisReks:


"sorry to go off topic here, but those tin foil hats are funny. if there was anything actually scanning someone's brain, those tin foil caps would actually improve the reception, since the edge of the aluminum foil would act like an antenna"

Thats just plain silly. An antenna is normally tuned and can both receive and transmit energies in the tuned band best, with a signal loss that resembles a bell curve with the optimum efficiency being in center of the tuned band.(there are variants that have application in real life utilizing fractions aka harmonics of the fundamental Fq but that would only confuse the issue.) As far as the human brain is concerned it generates signals at about 60 Hz.. with a relative measurable strength of micro volts. So... a metal hat would wouldn't couple these weak signals and in fact would act as a Faraday shield to decrease the availability of data. The interference from all the devices that generate electrical fields TVs, fluorescent lights , neon signs..ect.,would cancel out any effective specific targeting. There are other reasons that a schema like this wouldn't work but the basics here are reason enough to dismiss the effort =)



You could tho place a wire from the hat to a tooth that has a cavity in the vicinity of a strong signal generator ( AM radio station, mostly in Spanish or talk radio and hear stuff ). This happens all the time in relation to fillings or metal plates in the cranium, so as a receiver the hat will work somewhat ( hell the first radios used a cat's whisker as a signal detector.) as a device that transmits recognizable , useful data it is a flop.

SFB: "AND at what level would foil be defeated by higher levels of RF frequency and/or power?"

As far as raw power levels to over come the shielding effect, it would cook the brain ( it would also have to be specifically targeted or else all the humans in the vicinity as well as sensitive machinery would be fried.).

Another consideration is the fact that the brain interprets and initiate information in a 3 dimensional matrix, the brain itself ( kind of like a holograph) it is not linear like a newspaper or even speech, to gather this signal and couple it to a transmitter would take machinery that would make a Cray Supercomputer look like a stick.

Much more could be said about the non-feasibility of this silly line but suffice to say it is roughly equivalent to the proclamation that vampires can be kept at bay by the use of garlic cloves.

Thank You.

 

[Cain]

I think Brian hit the nail on the head:

I don't understand the question. These are just two very likeable, very Italian guys on the show, he makes a comment about only hitmen understanding it, I object to it, and somehow this indicates prejudice on my part?

It's off-topic anyway, let's not let him sidetrack the discussion

Their being Italian did not figure into my comment at all. Then suddenly, I'm bashing Italians (and gays). It's just mild sarcasm, admittedly no where the funniest comment in the world.