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Car Remote, hold against head - double range?

M

Mingon

Diamond Member
I know what your thinking odd topic but it is suitably HT as well as being quite interesting. In the UK their is a car program called Topgear, which lots of OT people have heard of due to their video's. In this weeks episode the presenter jeremy clarkson extended the range of his Car remote fob by holding against his head! The car was (i think) a Jaguar x/s type and nothing was rigged. He walked 45-50ft away from the car then held the remote up and locked/unlocked it. He then walked a further 15ft or so and it didnt work, BUT by holding it against his at ear level he managed to lock/unlock it. But why and how? is the signal being taken in through the ear and then directed out through the skull via eye sockets? Does the brain have any amplification effect? What are peoples theories
 
Originally posted by: Mingon
is the signal being taken in through the ear and then directed out through the skull via eye sockets?
Click to expand...

I hope you're joking. Anyway, I don't know what type of signal those remotes use, but I suppose it's possible that your body acts as an antenna, assuming you aren't grounded through your shoes (?).
 
Very odd effect. I think these transmitters operate on the 418 MHz band - so shouldn't be significantly affected by nearby objects.

Could be that the the presence of his head acts like a reflected changing the radiation pattern of the aerial in the key fob (in the same way that the reflector and other elements on a conventional [Yagi shape] TV aerial alter the beam pattern).

Could be that the aerial's optimum frequency is not quite right for the transmitter, and that the proximity to his head, alters the frequency band and improves the VSWR. These devices often use whip or loop aerials (which can be affected by their enviroment - particularly loop aerials). [edited - probably wrong originally].


Any RF engineers here, who can help?
 
I could extend the range on the one I had on my Dodge Ram by about 600' by holding the transmitter against an upright in the racking where I worked. (Home Depot)

The transmitter would only work from the 3rd row and closer from my truck when I was outside (about 150'). But if I went inside and held the treansmitter against an upright, it would work from almost anywhere in the building. (180,000 sq ft building with metal roof) anywhere else in the building (including 10' inside, where I can still see my truck line of sight) it did not work.

I used it for starting my truck on cold days when I was working. I would hold it against a beam in my department (which was about as far as you could get from my truck in the lot) and press the button fro 15 or so seconds. by the time I walked to the punch clock, and out to the truck, it was toasty warm.

This was with a "Viper" brand alarm. It was not just mine either. I taught 2 other people to do it who had the same keyfob as I did. they were amased it worked. One of them was a handicapped guy who whought it was awesome. (he drove an older 'vette that he always warmed up for 5 minutes before driving anywhere.)

It did not work against any other objects, including my head (the vacuum probably absorbs the energy) or the structural steel of the building uprights. (columns in the middle of the building supporting the roof)

the only thing I can think of is that the rack channeled the RF energy into the cieling where it radiated out from the roof in a circular pattern, which included the parking lot. It is just a guess since I know so little about RF it is not even funny.
 
Haha. My roommate showed me how he could extend the range of the transmitter for his garage door. He put it against his chin, held his arm towards the door, and pushed the button. We didn't take any measurments, but it sure looked like he extended his range.
 
I have a radio in my bathroom -- if I walk in there while it's on, the reception changes noticeably. If I grab the antenna, the reception changes noticeably *again*.

There's also a flaky halogen floodlight outside my apartment building -- if I walk by it on a warm night, it often blinks out.

Moral: your body acts as an antenna and can hold enough static charge to screw with all sorts of sensitive electronics (observe antistatic bags shipped with most PC parts). I assume Home Depot buildings, being basically one giant piece of steel, act similarly. 🙂

 
When I was in the Navy years ago There was a man in my outfit that would walk into a room with his transister radio tuned to a very annoying station at a very loud volume, set it down, and then walk out. The first chance I got I detuned the IF stages in his radio to where it would not play at all unless he was holding it in his hand and the capacitance of his body would tune it just enough that it would play at a low level.
 
Your body can both attune and amplify a RF signal. Dont forget the amount of iron in your blood, that is what makes the difference when you move around a bit and a radio station can go in and out on you. Likewise as I said your body can block, or attune, a RF signal.
 
RF antennae is still an area where most of the developement work is done by R&D(Rink and Dink). The scientific and engineering work only goes so far and then the empirical stuff out on the antenna range takes over. Because there are so many variables in play you can get almost any result you can imagine. I have seen old wire coat hangers outperform multi-thousand dollar engineered gems. Maybe this explains why antenna types tend to be a litle bit strange.
 
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