Recently a friend advised me that you could increase the transmission distance of a car’s remote unlocker by holding it against the bottom of your chin. Initially I dismissed it as silly, but curiosity got the better of me, so I tried it shortly thereafter. It seems to work.
I’ve compared distance I can be and still unlock(or lock) the car with the transmitter pointed forward (like a Star Trek phaser), up to my chin (buttons toward my neck), equal height as if under my chin, but off to the right (arm perpendicular to ground). I’ve also repeated it several times, and in different orders to remove the battery as a confound. Disturbingly, it seems to be true.
Can anybody corroborate the tests results? Can anyone offer a reason why this (may) be true? I drive a 93 volvo 850, if that matters.
I can corroborate your results, and I’ll do you one better. Try sticking out your arm when you do it, it works from even further away. What exactly this proves, I am not sure. I like the transmitter theory.
A few google searches confirm that this a common phenomenon; it seems that many dealers now tell new buyers about this “feature.” Several explanations are offered from less-than-credible sources: dental fillings, shape of the skull, etc. But it looks like the best explanation is simply that your body amplifies the transmission (which is, I believe, why TV reception will change when you touch the bunny ears, etc.)
Side note: This —> ";j " is a happy orthodox jewish man?
I tried this today with my VW Passat and dammit it works. Off to the side, above my head, no effect. Just at the chin. Tres bizarre. If one’s body is working as a transmitter, why are the arm and hand not enough?
I’ve never tried it, but I’ve heard it from enough different sources that I believe it really happens. I don’t believe that your body acts as a transmitter though. That would imply that the RF waves are generated by your body, which I can’t see a mechanism for that to happen with. What I could see happening though is that your body acts as a larger, better antenna, allowing more of the energy from the oscillator inside the hand held remote to end up as radio waves. There might be a bit of RF reflecting going on too. A small, simple antenna will tend to radiate equally out in all directions, where an antenna with a reflector behind it will radiate more in one direction, thus increasing the signal strength.
A simple test to see if the body is just focusing the RF energy would be to hold the remote in various orientations away from your head and measure how far away from the car you can be and still make it work, then hold it next to your chin and rotate yourself in various orientations and see how far away you can make it work. I have a hunch that with the remote up to your chin, the signal is going to be much more directional.
Try opening your mouth, sticking out your tongue and bugging yours eyes out when you do this. I think you’ll find you get very impressive effects, especially in really crowded parking lots where lots of people are milling about looking for their cars.
Seriously, though, my WAG is that your head is acting like a directional attenna, sort of like a microwave dish. As an experiment, take a large rectangle of aluminium foil and fold it in half. Then fold two of the corners to the middle. At the opening at the bottom, fold the foil up on both sides, leaving a large opening. Spread the construction out into a cone, place it on your head and repeat the procedure suggested in the previous paragraph.
Alternatively, you could try using the sheet of aluminium foil as a reflector behind your door unlocker and see if you get even better range, but I’m pretty sure my other suggestion will give more dramatic results.
Welllllllll, nnnnnnnnyyyyyyyyyyee no. As I understand RF, your body would either reflect or absorb radio wave energy. The only way I could see a body becoming an antenna would require direct contact with the circuit. I’m going to agree with your assessment that the RF from the remote is being reflected, extending the range of the remote.
[QUOTE=ryanhooper]
But it looks like the best explanation is simply that your body amplifies the transmission (which is, I believe, why TV reception will change when you touch the bunny ears, etc.) QUOTE]
My understanding on the TV reception is that you are changing the parasitic capacitance of the antenna. The same principle in effect on those lights that go on by touching the metallic base.
Things to test tomorrow:
If I’m making a directional antenna with my head, turning in any direction should render the increase in range null, since the antenna would point somewhere else. Thus try different orientations that don’t invole pointing in the direction of the car.
Change the orientation of the transmitter with regard to my head, but located in the same spot under my chin.
Change where on my head the transmitter is. Does it work as well over my hear? On my forehead? Will it work from the top of my head?
Foil hat/foil shield. My inner geek will make me try this one as well. If you see a guy with a foil hat on trying to unlock his car, say hi!. I’m friendly, if odd.
in chaos,
pandamonium
defn:
Remote: the device about 3cm x 5cm x 1cm thick. Buttons are on the large side
top: where the buttons are.
front: where the IR emitter would be on a normal TV remote (I know this is RF…)
I started close to the car, and increased the distance until such time as a remote held at arms length wouldn’t open the locks, yet under the chin would.
One thing I noticed as the distance from the car is increased: If I hold the remote at arm’s length, so the top is up and the front is pointed toward the car, the range is short Same is true for any sides facing the car. If the top or bottom faces the car (any orientation), the range is much better. Based on this, I suspect the remote is very directional in the ‘up’ and ‘down’ directions.
With top facing my neck, and me facing different directions, it appears any direction works (including away from car), thus casting the directional aspect into doubt. To continue this test, it also appears that any rotation of the remote on my chin also causes the car to open.
No. Look at a Yagi antenna. See all those elements that aren’t connected to the transmission cable? These are called passive, or parasitic, radiators. They absorb and re-emit RF like the driven element(s) in the antenna, but have no direct electrical connection. I suspect a similar mechanism is at work here, as e_c_g suggests.
In taking recently to someone who is doing work on antennas, he told me that humans are essentially large dielectric. Thus putting the remote to my chin causes the transmitter in the remote to load my head and act as a broadcast antenna. He went on to say that it would work better if I could load my entire body, and suggested I would get the best results if I inserted it rectally. The proof is left as an exercise.
Looks like Vlad/Igor and Engineer_Comp_Geek had the right ideas.
in chaos,
If that’s the case, then maybe your body is serving as a reflector and not a transmitter. Q.E.D.'s Yagi explanation is also intriguing. Then again, maybe I just like to say Yagi. Yagi Yagi Yagi.
Seriously, though, the strong signal coming from the bottom of the clicker goes straight out, and the equally-strong signal coming from the top hits the meat antenna (that’s you) and either reflects off of you in the right direction, or drives your jawbone/neck into transmitting. Try replacing the human body in the experimental setup with an aluminum foil corner reflector and/or other materials to see if your results vary at all.
I don’t pretend to understand the principles behind this,but we used the L.P.A. in the Army as a directional antenna that would actually boost the signal a … classified … degree. I wonder if your hand isn’t acting like one of these critters?
Your body is reflecting some of the signal that is being transmitted rearward from the transmitter. This is due to the difference in dielectric constant of air (which has a dielectric constant of approx. 1) and water (which has an extremely high dielectric constant of approx. 80).
You are in the transmitter antenna’s near field. Weird, unpredictable things can happen in an antenna’s near field. Perhaps your body is changing the antenna’s characteristic impedance for the better.
I might buy the reflection point if the signal were directionally strong. In my non-exhaustive tests, it didn’t matter which way I was pointing in relation to the car (assuming a constant orientation between me and the remote i.e. remote to my chin)
I need to go read up on near field effect. And go to work and stuff.
in chaos,
It doesn’t matter. If the pattern is non-directional, then some of the energy will be beaming in your direction. If nothing is in the way, the signal will continue traveling in the opposite direction of the car. But if your body is “in the way,” some of the energy will bounce off you (due to the dielectric constant ratio between you and air) and go toward the car.
