Put key fob to chin to increase range!

I actually measured this effect with a network analyzer (instrument used to measure the effectiveness of power transfer of radio frequency signals from one component to another, for example transmitter to antenna) many years ago. I had a VHF antenna from a walkie-talkie that was short stub; I held it out in my hand and it gave a reading that indicated it would be a lousy antenna. I then held the antenna next to my head, much as it would be if I were using a walkie-talkie to my mouth and ear, and the reading indicated that it was now a "good" antenna. So it was clear that the proximity to the head affected the impedance match (technical term, but basically meaning that there was efficient power transfer) of the antenna.

I haven't really thought about the actual cause, other than that the body has moderately conductive fluids and so naturally affects radiation patterns and impedance match of antennas. Here's a couple of hypotheses as it relates to the "chin" effect. 1) The transmitter antenna in the key fob is nowhere near big enough to be a good antenna at the operating frequency (you need a certain length for each frequency), so any extension of the effective antenna length (such as coupling to the head) improves the ability of the antenna to radiate its signals by getting closer to the optimum length. 2) The fob under chin method might work as an antenna + reflector (like satellite dishes); here what might be happening is that the radiated signal is sent out both toward the car and toward the head, the portion that meets the head (a large conductive body) is reflected back in the forward direction (away from the head), so that it adds to the power already going in the forward direction (toward the car), effectively increasing the range.

 

This is an interesting thread. On jobsites, we would always wonder why the radio worked better when the antenna was in contact with our body. Never tried it with our chins. For that matter, we never tried it with our peckers, either!

edit: will this concept work if your skull is encased in fruit like a pomelo or watermelon?

 

I always second doubt my self if I locked my car. Method works like charm.

 

So the chin is key?

Lay on the ground and then use your chin theory, you'll see my point.

 

Bwain twomor or less range. I'll take less range please

 

LOL

Hell some people would even result to actually putting the key in the door. "Bwrain wramage drocter? Verally? Rye wrididn't I ruse ra key? UH BLAAAAAAA"

 

Very interesting. One of the projects I worked on was aftermarket key fobs for cars. They pretty much all use custom chips, but the chips are available on the surplus aftermarket, as are the datasheets. I was working on a dodge fob and when I looked at the OEM fob the circuit trace was precisely sized to the size the datasheet recommended. Its pretty interesting how they design antennas and its very much a black art. I would be very curious to know more about why it happens exactly

 

Still wrong.

Near ground against chin has much more range than in hand stretched upwards.

You could always actually try it.

 

I must have a disfunctional chin. This is the fourth time I've heard this and it NEVER works for me, lol. My car only loves my wife.

 

LOL the reason it works is because the signal is amplified through your vocal cavity just like when u talk ur voice is amplified. Holding it close to your adam's apple and looking towards the car works best. Not whatever stupid reasons some of you are making up about electrical signal antenna or whatever.

 

I tried this last night.

My car in an empty strip mall parking lot. Held remote at "normal" height - to my side around pants pocket level. Walked away from car until remote no longer worked.

Moved hand out in front of me - up to shoulder level. Remote began working. Walked further away until remote stopped working again.

Moved remote to chin. Still didn't work.

So, for me, working distance had to do with height of remote - not chin touching.

Sounds like a good one for myth-busters.

 

How do you figure?

That sounds like a real stretch to me - and I wonder if it's based on any data or one of those "I think it sounds right so it must be" type things. Yin and I have a fair amount of experience with electronics, and Yin did some experiments. So please back the assertion that we're "making up stupid reasons".

 

It may depend on the type of remote.

On the BMW, the key is the remote (the buttons are in the actual key), and the shaft of the key is electrically coupled to the button part. The original post was specifically about BMW's (which is what my fob is). I would imagine with other brands it may not work as well or at all if its one of those seperate fobs where you dont get an electrical connection to the fob when touching your skin.

 

BS. The remotes don't care where they are in relation to the body.

You guys can however tell me where the pot of gold is at the end of a rainbow. I'll split it with ya.

 

It's possible - I forgot to mention my test was not with a BMW - but instead a Nissan - and my Nissan has a separate fob that is not part of the key.

So is it the key (metal) that must be touching the chin thus making this electical connection?

 

I learned about why it works in one of my biomedical engineering classes, and theres actually a video on the internet somewhere about how it works that backs up my theory

 

You're going to have to find your video and post it as otherwise I'm unconvinced. It seems more likely you're confusing audio frequency acoustic waves versus radio frequency electromagnetic waves.

 

^ this isnt the vid i was talking about, but heres a vid until i can find the one I saw in the class

http://www.lifehacker.com/software/body-hacks/amplify-your-car-remote-signal-with-your-head-263259.php

 

I appreciate the effort, but that really doesn't demonstrate or explain why the signal is greater, only that the chin trick works.

 

Jeremy Clarkson did this on Top Gear, but instead of his chin, he put it to his head and it worked.