The Reason the Remote Worked: a 2006 Cookout Thread

[Rkolter]

As some of you may know, I took a group of cookout people to Cahokia Mounds (an old place where indians used to build mounds to live on). The highest mound is Monk's Mound, a good couple hundred feet up, and about a quarter mile or more from where we parked my car.

From the top of Monk's Mound, I was able to use my remote control to lock and unlock my car doors! Far off in the distance, you could see my lights turn on and off in response to the remote. It worked repeatedly and without fail.

On the way back, we did some testing and found my remote only worked from about 50-100 feet away. The people who were with me wanted to know why.

Here's why.

We were all thinking "If the signal is powerful enough to reach that far from atop the mound, it should logically be powerful enough to reach that far from the ground."

This is a dangerous statement to make. I did some thinking about that - if it was a radio wave that would be true - while you could get reflection of the wave that would interfere with the signal, that reflection could never interfere with the FRONT of the signal, since it takes time for the signal to get to the reflective surface and back, and nothing travels faster than light.

But SOMETHING was interfereing with the signal. Then I realized the error.

It's not a radio emitting device. It's not a radio control at all. It's an infrared control!

And now it makes sense. Infrared radiation (heat) comes from everything - the ground, trees, the car, pavement, people... from the ground, this can severely distort the signal and limit it's broadcasting range.

But from the top of the mound, there is nothing but air between me and the car. Yes, air also radiates heat, but it's still about the best case scenario you can get on Earth. The signal reached the car because there wasn't enough interference anymore to scramble the signal.

As proof, from the center of monk's mound I could still see my car, but was unable to control it. The difference was only 50 feet or so, but it was 50 feet of flat open ground.

I should add that as a new car, the remote had new batteries, which undoubtedly helped. Also, the car was parked at the edge of the parking lot, so there weren't other cars, or broiling hot pavement, between the car and the remote.

So there you have it - infrared not radio, and nothing to hamper the signal.

[RemusShepherd]

Are you sure? I thought most car remotes were low-power radio. You can test it by cupping it in your hands and activating it -- your hands are opaque to infrared.

I suspect the reason the remote worked is because of the lack of ground clutter. If you're in a parking lot, the radio waves are bouncing off of everything, including the ground, and by the time they reach the car the signal is garbled. From straight overhead you might get some bounces off the cliff face but that's about it. I wonder if the remote would work from 1000 feet away if your car was sitting in an open, flat field with nothing around it. I think it would.

The front of the signal would not get garbled, but these remotes send a string of digital information as a key -- that's why each remote only works for the one car. If the middle or end of the signal is garbled, the digital signature fails, and the car refuses to acknowledge the remote.

It could also have something to do with where the receiver is placed within the car. If it's underneath the hood, then any signal coming in from the sides has to travel through a lot of material. But any signal coming in from the top would only have to get through the hood to be received.

I wasn't there, so I don't know much about the conditions or angle you were experimenting with. I'll have to help you repeat the experiment next year.

[Rkolter]

Unless Kia is lying to me, my car uses an infrared remote.

[RemusShepherd]

Unless Kia is lying to me, my car uses an infrared remote.

Okay, then. Info from the source.

[Garneta]

Great thread!

[Rock_dash]

So, basically, it's what I said it was? That on the ground, bumps were scrambling the signal, but way up on the mound, there was nothing to get in the way?

[Rkolter]

So, basically, it's what I said it was? That on the ground, bumps were scrambling the signal, but way up on the mound, there was nothing to get in the way?

What you said was that the signal was reflecting off bumps and scrambling the signal but that wasn't right. The front of the signal would always be significantly ahead of the reflected signal that way, because for the signal to reflect, the signal must travel to the site of reflection, reflect, then travel back to the signal in order to scramble it. Nothing can exceed the speed of light and so the reflected signal can never overtake the front of the signal.

In actuality it's the ground itself (or its radiating warmth), not any particular irregularities in it, that causes the interference.

[Rock_dash]

So, basically, it's what I said it was? That on the ground, bumps were scrambling the signal, but way up on the mound, there was nothing to get in the way?

What you said was that the signal was reflecting off bumps and scrambling the signal but that wasn't right. The front of the signal would always be significantly ahead of the reflected signal that way, because for the signal to reflect, the signal must travel to the site of reflection, reflect, then travel back to the signal in order to scramble it. Nothing can exceed the speed of light and so the reflected signal can never overtake the front of the signal.

In actuality it's the ground itself (or its radiating warmth), not any particular irregularities in it, that causes the interference.

...so...

...I was right?

[Ian Moulding]

So, basically, it's what I said it was? That on the ground, bumps were scrambling the signal, but way up on the mound, there was nothing to get in the way?

What you said was that the signal was reflecting off bumps and scrambling the signal but that wasn't right. The front of the signal would always be significantly ahead of the reflected signal that way, because for the signal to reflect, the signal must travel to the site of reflection, reflect, then travel back to the signal in order to scramble it. Nothing can exceed the speed of light and so the reflected signal can never overtake the front of the signal.

In actuality it's the ground itself (or its radiating warmth), not any particular irregularities in it, that causes the interference.

...so...

...I was right?

Nay, for thou spaketh of distortions in the very earth itself reflecting the signal, when in sooth it was radiant energies rising forth from the earth which did lead to the effect.

[Rock_dash]

So, basically, it's what I said it was? That on the ground, bumps were scrambling the signal, but way up on the mound, there was nothing to get in the way?

What you said was that the signal was reflecting off bumps and scrambling the signal but that wasn't right. The front of the signal would always be significantly ahead of the reflected signal that way, because for the signal to reflect, the signal must travel to the site of reflection, reflect, then travel back to the signal in order to scramble it. Nothing can exceed the speed of light and so the reflected signal can never overtake the front of the signal.

In actuality it's the ground itself (or its radiating warmth), not any particular irregularities in it, that causes the interference.

...so...

...I was right?

Nay, for thou spaketh of distortions in the very earth itself reflecting the signal, when in sooth it was radiant energies rising forth from the earth which did lead to the effect.

Oooh, now why didn't you just say it like that in the first place?