# wow! chin "antenna" trick really works...



## MBR87 (Mar 30, 2004)

Yep...when my dad got his 5-Series like 4 years ago the dealer told us about that little trick...been using it ever since


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## dorkus (Sep 4, 2003)

Wolfcastle said:


> I only use it to check that I've locked my car in a parking lot at night. Pretty useless most other occasions.


not at all! it's great for opening the windows on a hot day. it's kind of slow, but with the extra range you can have them completely rolled down by the time you get to the car. it's also good if, like me, you're forgetful and always ask yourself "did i really lock my car?" more than 30 seconds after you've already walked away from it... 



> You don't want a couple of mormons waiting for you in your car. Creepy christians.


i'll grant you that. :yikes:



JetBlack330i said:


> I tried to duplicate yamato's theory this morning in the parking garage. There were too many people there and I didn't want to look like a dork, so I gave up.


i understand. i gave up trying not to look like a dork many years ago though.


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## yamato (Feb 11, 2003)

JetBlack330i said:


> Perhaps he didn't see it work?  :rofl:


 :rofl: this reminds me a tricky question someone asked me:

Any one can explain why you see lightning first before your hear the thunder?

Think.... think harder man..

answer: it is because your eyes are in front of your ears. :thumbup:


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## WBear (Aug 30, 2003)

yamato said:


> :rofl: this reminds me a tricky question someone asked me:
> 
> Any one can explain why you see lightning first before your hear the thunder?
> 
> ...


 
Couldn't it be that the speed of light is faster than the speed of sound? (by about 186000 miles a second)


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## dorkus (Sep 4, 2003)

WBear said:


> Couldn't it be that the speed of light is faster than the speed of sound? (by about 186000 miles a second)


yeah... i think it was a joke though.


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## FenPhen (Jan 13, 2004)

yamato said:


> Any one can explain why you see lightning first before your hear the thunder?
> 
> Think.... think harder man..
> 
> answer: it is because your eyes are in front of your ears. :thumbup:


Yeah... but your auditory processing is in the middle part of the brain (near your ears) but the visual processing is in the back of the brain away from the eyes. A joke, I know.


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## birdman3 (Mar 2, 2004)

Why don't we all just get it over with and say the biggest words we know


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## SoN][c (May 25, 2004)

yamato said:


> My hypothesis is that this is because your skull is used as a reflective surface very much like a dish transmitter. The skull's shape is similar to a dish, so it focuses the power to a certain direction pretty well.
> 
> To partially prove it, I tried not facing the car, this trick did not work.


hehe. The phenomenon is actually known as capacitive coupling. I could go into details with formula's and all, but I'm sure that would put you to sleep .

Essentially the key and your body act like two plates of a capacitor separated by an electrical insulator (your clothes and skin). It will actually work if you press it against any part of your body that is relatively close to the conducting interior of your body. Your neck and butt should work too (although maybe not as well)!

Once this electrical connection is made, your body then acts as an antenna which increases the range of the signal.

I seem to remember making this post on another thread... talk about deja-vu!!

Anyways, Dorkus & JetBlack... I studied Elec Eng too... you guys should remeber this stuff!!


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## JetBlack330i (Feb 8, 2002)

I'm not quite sure how the tip of a key and my body form any meaningfull capacitor. Worse, I can't feel (without mathmatical equations) how a capacitor increases the transmission range. If that could be proven, why didn't BMW simply added an extra capacitor in the key?
The part of the explanation that makes sense to me is that of my body becoming an antenna. But for that, I would need to be in (electrical) contact with the metal key blade. Trouble is, I tried putting the key on my thigh this morning, and it worked. Thick blue jeans are known to be bad electrical conductors, so... :dunno:


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## dorkus (Sep 4, 2003)

SoN][c said:


> Anyways, Dorkus & JetBlack... I studied Elec Eng too... you guys should remeber this stuff!!


yeah, i know...  well, i didn't do any RF, though i did take Analog, so i remember capacitive coupling... but no idea about RF propagation. :dunno:


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## JetBlack330i (Feb 8, 2002)

birdman3 said:


> Why don't we all just get it over with and say the biggest words we know


I'll start: unconstitutionalistically.


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## JetBlack330i (Feb 8, 2002)

dorkus said:


> yeah, i know...  well, i didn't do any RF, though i did take Analog, so i remember capacitive coupling... but no idea about RF propagation. :dunno:


Oh, I just realized SonIIc meant the RF signal is using the key blade as a transmission antenna and that signal jumps into my body, if it's close enough, through the air medium (capacitive coupling) and then uses my body as a bigger antenna. Hmmm... is that really possible? I'm no RF guy either (digital background).


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## dorkus (Sep 4, 2003)

JetBlack330i said:


> I'm not quite sure how the tip of a key and my body form any meaningfull capacitor. Worse, I can't feel (without mathmatical equations) how a capacitor increases the transmission range. If that could be proven, why didn't BMW simply added an extra capacitor in the key?


the capacitor effect doesn't enhance the transmission... i think he was just saying that's how the signal gets from the key to the conductive parts of your body (i guess your skeleton?).



> Trouble is, I tried putting the key on my thigh this morning, and it worked. Thick blue jeans are known to be bad electrical conductors, so... :dunno:


it's frequency dependent. remember impedance? for a capacitor, it's inversely proportional with frequency... e.g. taking it to its limit approaching zero, the impedance of an ideal capacitor is infinite at DC (0Hz), which is why caps block DC. for a 60Hz power wave, a small capacitor (such as jeans would provide) would not conduct much. for a 315Mhz carrier signal, it doesn't take much capacitive coupling for the signal to travel through the dielectric (in this case denim). you also have to take into account dielectric factor/losses, leakage current, etc. but those are minor factors for something as rough as a key to your butt.


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## JetBlack330i (Feb 8, 2002)

dorkus said:


> the capacitor effect doesn't enhance the transmission... i think he was just saying that's how the signal gets from the key to the conductive parts of your body (i guess your skeleton?).
> 
> it's frequency dependent. remember imedance? for a capacitor, it's inversely proportional with frequency... e.g. taking it to its limit approaching zero, the impedance of an ideal capacitor is infinite at DC (0Hz), which is why caps block DC. for a 60Hz power wave, a small capacitor (such as jeans would provide) would not conduct much. for a 315Mhz carrier signal, it doesn't take much capacitive coupling for the signal to travel through the dielectric (in this case denim). you also have to take into account dielectric factor/losses, leakage current, etc. but those are minor factors for something as rough as a key to your butt.


Yeah, I just realized that.
You don't have a longer word than mine, but if I put together all those nerdy words you used, you win. :rofl:


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## SoN][c (May 25, 2004)

JetBlack330i said:


> I'm not quite sure how the tip of a key and my body form any meaningfull capacitor. Worse, I can't feel (without mathmatical equations) how a capacitor increases the transmission range. If that could be proven, why didn't BMW simply added an extra capacitor in the key?


I am not saying that the capacitor is increasing the range. I'm saying that capacitive coupling is used to make an electrical connection between the transmitter in the key fob and the electrical core of your body.

Would you like the equations? 



JetBlack330i said:


> The part of the explanation that makes sense to me is that of my body becoming an antenna. But for that, I would need to be in (electrical) contact with the metal key blade.


The electrical connection is made by capacitive coupling. The increase in range is due to the electrial core of your body acting as an antenna, which is electrically connected to the transmitter of the key fob through capacitive coupling.



JetBlack330i said:


> Trouble is, I tried putting the key on my thigh this morning, and it worked. Thick blue jeans are known to be bad electrical conductors, so... :dunno:


Correct. Thick blue jeans are insulators. An insulator between the two plates are required for capacitive coupling to work.

HTH


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## dorkus (Sep 4, 2003)

i think he gets it now...


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## SoN][c (May 25, 2004)

JetBlack330i said:


> Oh, I just realized SonIIc meant the RF signal is using the key blade as a transmission antenna and that signal jumps into my body, if it's close enough, through the air medium (capacitive coupling) and then uses my body as a bigger antenna. Hmmm... is that really possible? I'm no RF guy either (digital background).


Well the keyblade is being used as one plate of the capacitor. The insulation, which is required for capacitive coupling to work, is your skin and your clothes. The second plate is the electrical core of your body.


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## SoN][c (May 25, 2004)

dorkus said:


> i think he gets it now...


sorry, didnt see the other posts until just now.


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## Salvator (Oct 14, 2003)

birdman3 said:


> Why don't we all just get it over with and say the biggest words we know


What a bunch of sesquipedalians... 


*ses·qui·pe·da·lian*  ( P ) *Pronunciation Key* (s







n)

_n._ A long word.

_adj._

Given to the use of long words.
Long and ponderous; polysyllabic.

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Source:


> The American Heritage® Dictionary of the English Language, Fourth Edition
> 
> Copyright © 2000 by Houghton Mifflin Company.
> Published by Houghton Mifflin Company. All rights reserved.



*******>*******>*******>
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*Sesquipedalian*

sesquipedalian was Word of the Day on October 25, 1999.


Source:


> Dictionary.com Word of the Day



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*Sesquipedalian*

Sesquipedal \Ses*quip"e*dal\, Sesquipedalian\Ses`qui*pe*da"li*an\, a. [Sesqui- + pedal: cf. F. sesquip['e]dal, L. sesquipedalis.] Measuring or containing a foot and a half; as, a sesquipedalian pygmy; -- sometimes humorously applied to long words.

[Free Trial - Merriam-Webster Unabridged.]

Source:


> Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.



*******>*******>*******>
********>********>********>
*Sesquipedalian*

adj 1: given to the overuse of long words; "sesquipedalian orators"; "this sesquipedalian way of saying one has no money" 2: (of words) long and ponderous; having many syllables; "sesquipedalian technical terms" [syn: polysyllabic] n : a very long word (a foot and a half long) [syn: sesquipedalia]


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## JetBlack330i (Feb 8, 2002)

Er... your post above was sesquipedalian. :neener:
He asked for big words, and yours only has 5 syllables. :lmao:


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## Will_325i (Jan 27, 2004)

JetBlack330i said:


> But how do you explain yamato's claim that it didn't work when he wasn't facing the car?
> Perhaps he didn't see it work?  :rofl:


Put me down as yet another EE. Anyway, I assume (key word) that absorption was involved.

Empirically, I have "proven" the chin trick to work. Some say it's false and the only reason it "helps" is because you're lifing the transmitter to a higher level than normal. NO! I've tried just lifing it without touching the chin and it doesn't work.

If someone sold an affordable, honest to goodness antenna BOOSTER, I would buy it !


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## SoN][c (May 25, 2004)

yamato said:


> I am starting to feel uncomfortable without understanding the details on why this chin thing work.
> 
> As mentioned earlier in this thread, how many of you tried to verify this chin method is directional sensitive?
> 
> Eventually, if this dicussion doesn't go anywhere, I will start calling BMW NA to find out the answer.


Did you read my post? I already explained it....


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## Salvator (Oct 14, 2003)

yamato said:


> thanks. i sent an email to him last night. pm me when you see my (our) question on paper.


I'll keep my eyes open for it! :thumbup:


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## yamato (Feb 11, 2003)

SoN][c said:


> Did you read my post? I already explained it....


yes, but sorry I don't think that was sufficient to turn off my curiousity on this topic. I still can't use your theory to explain my observations, which are: this trick only increases the range in the direction I am facing, and I tried to use other part of my body, it didn't work.

oh btw, maybe when I feel like it, i can try one more thing to verify this capacitive coupling theory. Stick the key into my nose and check the range. This increases the contact area between the body and the key, hence should have a much better coupling effect. :rofl: :rofl:


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## JetBlack330i (Feb 8, 2002)

yamato said:


> yes, but sorry I don't think that was sufficient to turn off my curiousity on this topic. I still can't use your theory to explain my observations, which are: this trick only increases the range in the direction I am facing, and I tried to use other part of my body, it didn't work.


How did you prove that it only works in the direction you are facing? Did you have a helper next to the car to tell you if it worked when you're not looking at it?
I proved that it works when I touch my hip. Does it still matter where I'm facing? :dunno:


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## yamato (Feb 11, 2003)

JetBlack330i said:


> How did you prove that it only works in the direction you are facing? Did you have a helper next to the car to tell you if it worked when you're not looking at it?
> I proved that it works when I touch my hip. Does it still matter where I'm facing? :dunno:


yes i had someone standing next to me to watch if the tail lights flashed. Or you guys can just use a mirror to try this.


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## azurribaggio (Dec 29, 2003)

Salvator said:


> If it makes you feel any better, I have known about this trick for years, prior to my purchase of my BMW... It works on my Land Rover as well, and works on a variety of other vehicles... The friend who told me about it used to unlock his Jeep Cherokee from across the parking lot for many years... It's nothing new, and undoubtedly no more hurtful than the rest of the radio, satellite and microwaves that are traveling through you EVEN NOW! IN FACT, I'D RECOMMEND THAT YOU RUN OUT RIGHT NOW AND WRAP YOUR HEAD IN ALUMINUM FOIL TO STOP THE RAYS FROM MELTING YOUR BRAIN!!!!!
> 
> (j/k)


The SYNAPSE which runs through your brain is what extends the signal.


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## Spectre (Aug 1, 2002)

azurribaggio said:


> The SYNAPSE which runs through your brain is what extends the signal.


A synapse is neuron-neuron junction and you have many of them (I assume :rofl: ). However, the effect really works because of your spine. It's a nice vertical antenna of just the right wavelength.


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## jeffreyslc (May 27, 2002)

Spectre said:


> A synapse is neuron-neuron junction and you have many of them (I assume :rofl: ). However, the effect really works because of your spine. It's a nice vertical antenna of just the right wavelength.


It is not synapses or spinal cords. The RF couples into your eye balls which act like parabolic directional antennas, which obviously explains why it works better if you are facing your car. If someone could 'see' RF there would be two beams shooting from your eyes to your car.


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## Iniquity (Sep 3, 2003)

*some facts for you guys...*

I don't know the specifics of the bmw transmitter/reciever design.. but here's some basics of RF design/analysis to spur your imaginations further.

1. RF is effectively on the range of 300 MHz - 500 GHz (not sure about that upper bound). Typically, the higher the frequency the smaller the components because the wavelength decreases. (You should see the size of the diodes needed for a design at 2.4 GHz.. it's about the size of the "U" in the United States of America printed on the back of a penny).. Soo.. keeping this in mind, the size of the key, it would be safe to assume it's operating at RF levels.. but most likely not in the GHz range..

2. Don't worry about brain cancer and such... the amount of power being transmitted from the key is miniscule compared to your cell phone.

3. The human body is a horrible antenna. Humans are composed of mostly water, even your head. What this means is that the human body is a huge dielectric material. Dielectrics do reflect RF waves and also allow transmission. HOwever, depending on the dielectric material, all it does is introduce losses in power. Water is a poor dielectric for RF transmissions.. especially organic material. Your head will absorb most of the energy transmitted from the key. Where does this energy go? Simple, heat. This is how a microwave oven works, with one exception, it's tuned specifically for the frequency of water.

4. Why and how it works, I have no idea. I would need to study the human body. RF transmissions depend on transmission lines for their, uh, transmission. One such type is your coaxial cable for your tv. Another type is rectangular. I imagine this is what the head is mimicking. A rectangular waveguide is a hollow device, usually air filled (dielectric constant (permittivity) for freespace = 8.85x10^-12). This is a lossless case, so the incident power equals the transmitted power.. in other words, the reflection coefficient is zero. However, in our case, the skull/bones is the waveguide with the dielectric material being water and human flesh.. which has a high loss.. So in actuality, the power transmitted with the chin trick is less than what you would have if the key were pressed alone. However.. i'm guessing it's just more direct which is why it gives further range..(see below)

5. The body of the key itself is most likely used as the antenna, in which case it would be classified as a dipole type antenna. Although initially you will have less loss with just the key itself, dipole antennas are more subject to reflection because they transmit in multiple axes. Depending on the surrounding area, the actuall amount of signal that reaches the target varies. Ever notice that some times you have good range and other times you gotta be practically next to the car? Materials affect the planewaves significantly. So, although, like I stated above that less power is being transmitted when you use the chin trick, it is apparently on average more power, than what reaches your car after the scattering and reflecting losses takes its toll on when you use the key alone.

6. Finally, RF waves act more like optics than sound waves.... there are actually several common equations...

Again.. this is all theory on how it works.. i really would need to research the human body to find a definitive answer..


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## Iniquity (Sep 3, 2003)

jeffreyslc said:


> It is not synapses or spinal cords. The RF couples into your eye balls which act like parabolic directional antennas, which obviously explains why it works better if you are facing your car. If someone could 'see' RF there would be two beams shooting from your eyes to your car.


you're actually probably not too far off... just incorrect terminology.... see above post..


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## dorkus (Sep 4, 2003)

FYI, the key's transmitter carrier frequency is 315MHz, at least on my keys. it should be marked on the back.


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## Iniquity (Sep 3, 2003)

dorkus said:


> FYI, the key's transmitter carrier frequency is 315MHz, at least on my keys. it should be marked on the back.


So it's just barely in the RF range...

hmmm.. so a relatively large wavelength... another theory..

the amount of power recieved is also highly dependent on "matched components"

i'm not sure where the recieve is for the car, or how big it's antenna is... but using the human body may also better match the transmitted wavelengths to the antenna. Antenna and waveguide geometry play huuuuuge roles in determing power transmission... geometry affects things such as polarity, wavelength, planwave directions, etc...


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## dorkus (Sep 4, 2003)

Iniquity said:


> So it's just barely in the RF range...


actually, strictly speaking RF can be as low as 10kHz. AM radio is only in the hundreds of kz after all, and clearly that is "radio." did you mean a specific RF band, e.g. UHF? i think 315Mhz actually falls between VHF and UHF... there is a gap of a couple hundred MHz used for various misc. services.


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## Iniquity (Sep 3, 2003)

dorkus said:


> actually, strictly speaking RF can be as low as 10kHz. AM radio is only in the hundreds of kz after all, and clearly that is "radio." did you mean a specific RF band, e.g. UHF? i think 315Mhz actually falls between VHF and UHF... there is a gap of a couple hundred MHz used for various misc. services.


When I refer to RF i'm referring to microwave engineering design.. the propagation of planewaves... field magnitudes.. etc.. etc..

not audio/radio.... different.. yet kind of the same.. .

example.. just last year my team and I were designing two wireless power recievers.. one operating at 1 MHz.. which is considered to be analog and use lumped components.. and a second one operating at 2.45 GHz.. the RF design....

just different terminology I guess between radio/audio people and engineers?!?! :dunno: .. kind like how in math classes.. one variable means something different in physics..


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## JetBlack330i (Feb 8, 2002)

Iniquity said:


> So, although, like I stated above that less power is being transmitted when you use the chin trick, it is apparently on average more power, than what reaches your car after the scattering and reflecting losses takes its toll on when you use the key alone.


:blah:
Still doesn't answer why the trick works.
Looks like you need a chin trick for all that theory. It's scattering and reflecting all over, but not reaching the target. :rofl:


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## Fast Bob (Jun 4, 2004)

JetBlack330i said:


> :blah:
> Still doesn't answer why the trick works.
> Looks like you need a chin trick for all that theory. It's scattering and reflecting all over, but not reaching the target. :rofl:


Simple....you need a "ZHP chin" for maximum range....
Line-of-sight and elevation (relative to the car`s position) will determine the range....I parked my car at the end of my driveway, about 135 ft. from the street, and 3-4 ft. above street level....I stood by the street, and touched the key to my chin....nada....but extending my arm straight up and using my open palm as a reflector, it worked fine.

Regards,
Bob


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## Salvator (Oct 14, 2003)

Fast Bob said:


> Simple....you need a "ZHP chin" for maximum range....


I bet he can open BMW doors from across the state! :rofl:


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## msilva (Aug 5, 2002)

Salvator said:


> I bet he can open BMW doors from across the state! :rofl:


I bet Bruce could open doors in Europe.


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## wag-zhp (Apr 8, 2004)

Salvator said:


> I bet he can open BMW doors from across the state! :rofl:


 :rofl: I almost posted the same thing! :rofl: :thumbup:


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## Fast Bob (Jun 4, 2004)

Salvator said:


> I bet he can open BMW doors from across the state! :rofl:


Scary fact : If you`ve ever seen her in profile, Drew Barrymore has Jay Leno`s chin....I bet she gives good range....

Regards,
Bob


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## Salvator (Oct 14, 2003)

Fast Bob said:


> I bet she gives good range....


I bet she "gives" other things good, as well... :eeps: :slap:


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