My uncle showed me this years ago and ever since I have sworn by it: we were coming out of an Astros game, trying to find his car, using the tried-and-true method of pushing the car alarm remote button and homing in on the chirps the car would make. Except we weren’t close enough for it to be in range. So my uncle says something to the tune of “Check this out,” and then opens his mouth wide and places the remote doohicky behind his chin, right underneath his open mouth, flush against the skin. He then presses the button and CHIRP, CHIRP, we’re golden. I have always found this to increase the range at which I can lock my doors or whatever, and I assume that the mouth acts as some sort of parabola-type echoing device. My question is, does this really work or is it in my head? And if it does work, what are the exact physics of it?
PS: Sorry about the truncated title and the bad puns.
Most likely your body is acting as a 5’11" antenna, which is magnifying the teeny little antenna in the transmitter.
Sometimes you can do the same thing by getting close to an AM radio with a cheap little coiled wire antenna. The signal improves.
I don’t see how using your mouth is any better of an antenna than your arm. That said, I found out that my RKE range is significantly enhanced if I put the RKE transmitter against someone else’s radio arial… Same basic principle, I suppose, but you don’t look quite as goofy.
chriszarate wrote:
Is this some new kind of slang? My brain can’t parse it.
kunilou, dont those things use infa red though?
I don’t know why it works, but it does. I can generally get twice the range or more by using the chin method, however, I have never had to open my mouth for it to work.
My guess is that, like others have posted, your body is acting like a large antenna, hence the better range.
JoeyBlades mentioned using the radio antenna on another car to have a similar result, but this has not been nearly as effective for me. That is OK, since I could care less how pressing it to my chin makes me look. 
I take pride in my goofiness.
Nukeman: VERY few of the transmitters use IR. Most of them are RF
I’ve been doing this for ten years and it’s second nature now. I forgot I was even doing it until I read this thread.
Now that explains all the odd looks I get in parking lots.
I simply place the transmitter under my chin, mouth closed, and press. Easy to test. It works for me. I always assumed it was because the head was a better antenae than the hand and arm.
So… I’m not the only wacko out there…
CurtC: The alarm disarm sounds on a car always sounded like “CHIRP” to me. No slang. As for “we’re golden,” I’ve always used that to mean “things are going very well.” Maybe it’s a Southern thing?
Everyone else: At the risk of sounding like an (even bigger) idiot, RF is radio waves? Or something else? If it’s something else, any chance I’m gradually giving myself cancer of the mouth? And we’re sure that it’s a matter of your head being an antenna, but is it magnifying or resonating the signal somehow? In other words, what’s an antenna, exactly? I have monkeys we can test on, if necessary.
Ive GOT to try this now. Reading the SDMB makes me do the weirdest things.
Umm, maybe you want to try it while you’re holding that pencil a few millimeters from your nose.
chriszarate: IIRC, RF is Radio Frequency.
I believe these devices are indeed RF and not IF (Infrared Frequency.) But I don’t know for sure. The evidence I have is that I can open the car without taking the key fob out of my pocket. Try changing your TV channel with the remote wrapped up in your bathrobe. It’s infrared and won’t penetrate solid objects.
Tinker
sigh
Tinker
I was wondering how so many people were frying their brains with using illegal substances. No wonder you can’t remember where you left the car.
Infra red is your TV remote and you will notice you have to point it to the receiver hole in the TV and if you cover the receiver with anything it will not work. It definitely will not work from the next room. Does that answer your question or do I have to be more explicit?
yes. you can bounce the infa red off walls and stuff, especially if it is a white wall. try pointing the remote at the wall behind you or at the ceiling. Maybe the infa red might be bouncing off the curve between your chin and your kneck
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RF stands for Radio Frequency so yes…radio waves.
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It’s doubtful you’ll give yourself cancer with this. Your remote for the car is VERY low power. I find it extremely unlikely this would cause cancer or other ill effects. Don’t take my word for it though. Here’s an article from Scientific American on the subject of EMF (electromagnetic frequencies) and health. http://www.scientificamerican.com/askexpert/medicine/medicine25.html
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As for your body resonating or amplifying the signal I’d have to say no but I’m no expert either. In general the bigger the antenna the better the reception/transmission (antennas both transmit and receive). Your body (or head) is bigger than the little antenna in your remote. So, while your not amplifying the signal per se you are broadcasting with a bigger antenna. Why your nerves can do this I don’t know except to say that humans (any animal actually) run on electricity. Obviously some property of electricity is being exploited here.
I’ll stop now as I’ve already gone beyond my knowledge base.
of course humans conduct electricity, but not just through their nerves. Water conducts electricity, we are mostly water, and our skin is covered in a thin layer of water.
Jeff wrote:
Actually, it’s not just about power, it’s also about the frequency of radiation. Radio waves (and light) are forms of radiation. For the purposes of this discussion we can break radiation into two categories ionizing and non ionizing. What this essentially means to you is that ionizing radiation causes cell damage. X-rays and microwaves are forms of ionizing radiation, which is why your dentist wears a lead apron (it’s not a fashion statement) and why it’s not a good idea to put a cat in a microwave oven. RKE (Remote Keyless Entry) transmitters and cell phones emit non ionizing radiation. Based on all known science, these are not dangerous. If someday we find out that even non ionizing radiation can be harmful, then we’re all in trouble, because we are exposed to non ionizing radiation from thousands of sources every day of our lives. TVs, radios, digital watches, personal computers, telephones, pagers, automobile electronics, electric lights, and many, many more sources.
BTW, when it comes to antennas - bigger is not necessarily better. I suspect that whatever mechanism is increasing the power of the radio signal when you put the RKE to your chin is not related to the size of the antenna. I’ll have to ponder this some more.
chriszarate, what did you intend the title to be? I can edit it in and fix it. By the way, congratulations: You’ve managed to post a physics question which has left me completely stumped-- Not a common occurence
Actually, JoeyBlades, microwaves aren’t ionizing… They’re actually radio waves themselves, at the short-wavelength end of the spectrum (hence the name). They heat food via a resonance with water, not ionization. Otherwise, I agree with you: Nonionizing radiation is a nonproblem.
Sorry guys, I don’t think the antenna theory works. The “antenna” is the same size no matter if the transmitter is in your hand or against your chin. Not to mention I doubt the signal is carried through the plastic into your body efficiently.
My theory is that you’re just comparing the effective range of the RKE from somehwere around waist level, including all the interference from ground effect, and obstacles such as cars and foliage, to the range when you’re holding it at around 6’ in the air. The fact your chin is there is coincidental.