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Geek Culture / Question to an RF Nerds out there...

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SageTech
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Joined: 3rd Dec 2004
Location: Orlando, Florida
Posted: 6th Sep 2009 22:46
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Hi all,

I am in no way an expert in anything having to do with Radio Waves and the like, but I'm sure somebody here can answer my question. For those of you that have key-less entry in your car, you'll know how annoying it is when you need to unlock your door but have to get so close you might as well be unlocking it with the key.

Well, I had a bit of an idea. In my current car setup, I do not use the FM/AM Radio Antenna at all, in fact the wire lead going into the dash is just taped and coiled up at the moment. So, I was thinking, why not tie the key-less entry antenna to the Radio antenna? Would increasing the length of the antenna adversely effect range or boost it?
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NeX the Fairly Fast Ferret
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Joined: 10th Apr 2005
Location: The Fifth Plane of Oblivion
Posted: 6th Sep 2009 22:54
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The aerial is likely optimised for the wavelength it is to operate on. This is why 35mHz transmitters have huge aerials and 2gHz have four inch aerials; the wavelength is shorter because the frequency is higher.

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monotonic
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Joined: 24th Mar 2006
Location: Nottinghamshire, England
Posted: 7th Sep 2009 22:15 Edited at: 7th Sep 2009 22:17
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Indeed, the aerial should be approximately 1/4 the wavelength IIRC. So a wavelength of a 2GHz RF signal requires an aerial which is 0.0375m (3.75cm) in length.

Quote: "2gHz have four inch aerials"


The wavelength is approximately 15cm, L = C / f (Couldn't insert lambda).

01100001 01101110 01101111 01110100 01101000 01100101 01110010
01110000 01101111 01101001 01101110 01110100 01101100 01100101 01110011
01110011 01110011 01101001 01100111
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Phaelax
DBPro Master
22
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Joined: 16th Apr 2003
Location: Metropia
Posted: 7th Sep 2009 22:18
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You could replace the battery in your keyless remote.

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monotonic
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Location: Nottinghamshire, England
Posted: 7th Sep 2009 22:34
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Or take the advice of Jeremy Clarkson and stick the remote against your head, apparently it increased the distance by 1/3.

01100001 01101110 01101111 01110100 01101000 01100101 01110010
01110000 01101111 01101001 01101110 01110100 01101100 01100101 01110011
01110011 01110011 01101001 01100111
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Neuro Fuzzy
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Posted: 8th Sep 2009 02:23
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Heheh, that's worked for me actually. My dad told me about that, so i stood far enough away from the car so that i couldn't beep it. Then i put it up to mah head, and the car beeped

No clue why though...
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Benjamin
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Location: France
Posted: 8th Sep 2009 05:19
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Attach this to your car.
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Phaelax
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Posted: 8th Sep 2009 20:39
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Quote: "Or take the advice of Jeremy Clarkson and stick the remote against your head, apparently it increased the distance by 1/3."

I tried that, it didn't work for me. Guess my head was too dense.

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bobbel
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Location: In my DBPro case xD
Posted: 9th Sep 2009 00:03
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Lol @ Benjamin. Call me when you succeed XD

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Mnemonix
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Joined: 2nd Dec 2002
Location: Skaro
Posted: 12th Sep 2009 03:34 Edited at: 12th Sep 2009 03:34
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Quote: "Attach this to your car. "


I followed Benjamins advice...

Needless to say the owner of the radio telescope I stole was very angry indeed.

I attached the dish to the underside of the car, which "interferes" with many aspects of the cars functionality.

I gained an audience as I was undertaking this engineering endeavour. Various responses shouted to me were:

"What are you doing?"
"Why are you doing this?"
"Couldn't you just use a sky dish?"
"Thats a big jack you have there, where did you get it?"
"Oi, give me my radio telescope back immediately!"
"Oi, what have you done to my car you fool!!"
"Oi, you are under arrest"

The point is that it just did not work on any level and neither this or any other of Benjamins recommendations should be attempted, ever, unless it is by somebody competent like me.

I got off with community service, which I spent fixing HAARP to a pickup truck.

Mnemonix
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