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Why does holding a key fob to your head increase its range?

physics.stackexchange.com

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Re: Why does holding a key fob to your head increase its range?

#31

Post by initplus »

hammock wrote: post #18
acomjean wrote: post #12

Earlier quoted context omitted.

I suspect not. Its a short burst of rf and not done very frequently. (I use this technque with an key fob near an open mouth probably 4 times a year.. Thanks Car talk. https://community.cartalk.com/t/does-the-remote-entry-work-b... Your phone is probably worse.

Why would the duration or frequency of the burst matter if RF is harmless?

RF is harmless below the point where it directly heats tissue.

Having a full strength cell tower transmitter inside your home is not safe due to the intensity of the transmission, it will directly heat tissue inside your body.

Re: Why does holding a key fob to your head increase its range?

#32

Post by zontorol »

Buttons840 wrote: post #27
behnamoh wrote: post #10

In the movie LalaLand, they mention that this is dangerous (causing diseases). Is that true?

Should we worry about a radio transmission powered by a 3 volt battery while taking on our phone?

A phone battery is 3.8 volt. No worry, right?

Re: Why does holding a key fob to your head increase its range?

#33

Post by farkanoid »

Buttons840 wrote: post #27
behnamoh wrote: post #10

In the movie LalaLand, they mention that this is dangerous (causing diseases). Is that true?

Should we worry about a radio transmission powered by a 3 volt battery while taking on our phone?

But my remote contains a 12V battery /s

Re: Why does holding a key fob to your head increase its range?

#35

Post by drivers99 »

behnamoh wrote: post #10

In the movie LalaLand, they mention that this is dangerous (causing diseases). Is that true?

https://www.youtube.com/watch?v=w5SRH6Ac1LI&t=25s Love that movie. I didn't remember that so I found the scene. The character's joking / trying to mess with the other person. "You gotta put that thing to your chin. It makes your head into an antenna, so... I think it gives you cancer but you find your car faster. I mean, you don't live as long but you get where you're going quicker so it all evens out. Just a suggestion." At 5:15 in that video she tries it and it works.

Re: Why does holding a key fob to your head increase its range?

#36

Post by aqfamnzc »

plugin-baby wrote: post #34
piskov wrote: post #24

Makes one wonder about bluetooth headphones

IME Bluetooth headphone volume increases if you put them near your head

I find this especially true when moving them close to the ears. Could it be the dished shape?

Re: Why does holding a key fob to your head increase its range?

#37

Post by Buttons840 »

zontorol wrote: post #32
Buttons840 wrote: post #27

Earlier quoted context omitted.

Should we worry about a radio transmission powered by a 3 volt battery while taking on our phone?

A phone battery is 3.8 volt. No worry, right?

Good point. I don't know much about these things. Are the radio transmissions from a phone stronger? I would expect so, but don't know.

Re: Why does holding a key fob to your head increase its range?

#38

Post by cstejerean »

Buttons840 wrote: post #26
tempestn wrote: post #14

Earlier quoted context omitted.

That was my first thought too, but the OPs tests had the range only improving when held to the head.

I've had my fob fail to work multiple times while walking away from my car, so I take it out of my pocket and put it near my lower back and it works (even though I'm now even farther away because I'm walking).

That's slightly different though, sounds like fob went from being blocked by your body to no longer being blocked by your body.

Re: Why does holding a key fob to your head increase its range?

#40

Post by ratg13 »

Buttons840 wrote: post #6

It also works holding it near your torso, don't have to use your head. Although, the joke you tell your friends is that it only works if they open their mouth and stick out their tongue like a satellite dish. The fact that it works next to your torso made me think it was just a matter of bouncing half the radio emissions towards the vehicle, thus doubling the signal. Just like someone holding an omni-directional camp…

It’s just using the water in your body as an antenna.

You can see the same effect by holding the car remote to a water bottle.

You’ll notice the water bottle gives you about the same extended range as your head.

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