Has anyone boosted a car key-fobs range?

Discussion in 'Wireless & RF Design' started by bigcape, Oct 13, 2009.

  1. bigcape

    Thread Starter Member

    Sep 18, 2009
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    I did a search- no luck.

    I picked here cause it has to do with signals and ????

    Don't tell me to replace the batteries!:)

    Has anybody modified an auto remote key-fab to get longer range to lock/unlock or better yet find your car when you forgot where you parked?

    if nothing else just fo fun.:rolleyes:
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Have you reviewed the FCC regulations?

    John
     
  3. bigcape

    Thread Starter Member

    Sep 18, 2009
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    There is nothing in there that I read that says im stuck with my Mercedes key-fab which only works from about 2 parking spaces away cant work like my Porsche key-fab does from about 25 spaces

    If I missed something how about quoting it for me?

    Then agian maybe the fab works of of IR or something else and I don't know it
     
    Last edited: Oct 13, 2009
  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    What section did you look in?

    Did you read this part:
    John
     
  5. bigcape

    Thread Starter Member

    Sep 18, 2009
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    Are you serious or just bored?

    The section that couldn't fix my obviously failing key fab.

    Thanks for your input John.

    let me clairify just in case: I would like the "Periodic operation" of my mercedes fab to be equal to the "Periodic operation" of my Porsche fab. which is imprinted that IT complies with the FCC


    What would happen if I posted a question on this site asking how to get my RC airplanes control box that operates my plane at several hundred yards, continuously, to unlock my car?
     
    Last edited: Oct 13, 2009
  6. wr8y

    Active Member

    Sep 16, 2008
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    The key word in your post is Mercedes. I have the same problem, we all do. I don't know WHAT it is, but if its a Mercedes key-fob, two or three car lengths is about it.

    Same for the in-the-overhead garage door opener - easy to program, but about half the range of my handheld Sears opener.

    If we ASSUME that it's the key-fob and not an insensitive receiver in the car, I wonder if we can buy another fob (like a Porsche or Ford or whatever) and program it to our cars?

    In any event, it's a price I am willing to pay to drive a Mercedes.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    I'm sorry, you lost me there.

    Those regulations do not give instructions on how to fix a "failing" key fob. They do address, however, regulations governing your original question about how to modify a key fob transmitter to get greater range.


    John
     
  8. RiJoRI

    Well-Known Member

    Aug 15, 2007
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    Key fobs use RF. IR would limit it to line-of-sight.

    There have been rumors that putting the fob against your neck will extend the range somewhat. I have not verified this, but the theory is that your body works as a rather large antenna.

    --Rich
     
  9. bigcape

    Thread Starter Member

    Sep 18, 2009
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    Yes John, no they dont!

    Do you have a car with a remote key fab? If you do then go outside test it then come back and post your findings.

    I was not planning on debating FCC regs, but as long as this is where the thread is going then:


    "(1) A manually operated transmitter shall employ a switch that will automatically deactivate the transmitter within not more than 5 seconds of being released.
    (2) A transmitter activated automatically shall cease transmission within 5 seconds after activation."

    Can we unlock my car on the moon in this band as long as we dont hold the button down for more than 5 seconds?
     
  10. bigcape

    Thread Starter Member

    Sep 18, 2009
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    They say aiming it under your chin, but thats not LOS though?

    I have a newer Mercedes that will unlock even when it is 3 floors up through concrete while i'm still in the elevator!

    Does anybody like to have any fun around here?

    I dont know enough to play on my own. I was hoping to make some friends that would like be creative and share.
     
  11. bigcape

    Thread Starter Member

    Sep 18, 2009
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    (bolding and font size by bigcape)


    My question had ZERO to do with wanting any info on FCC regs, sorry chief.

    Besides you did not offer caution, that would have been kind. Instead you just asked if I had read the regs in less than 10 words.
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    As already pointed out it could be either the key fob or the recever in the car. Potential modifications of the fob would probably require mechanical and packaging modifications which might be difficult or impossible to accomplish. For example to boost the power output of the transmitter, the number of batteries could be increased. The current circuit components may or may not continue to be within their design limits. If you had to redesign the RF power amp it would probably take more test equipment than your Mercedes and your Porsche put together. My solution would be to do like the rest of us and drive a Honda -- grin!
     
  13. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    The regulations certainly do address modifications to cleared/licensed/exempt devices and regulatory requirements for performing such.

    This forum does not allow posts that effectively are asking how to circumvent laws.

    It is not a question of having fun, it is a question of obeying laws and regulations.

    If you want it repaired, take it to an authorized service center.

    John
     
  14. bigcape

    Thread Starter Member

    Sep 18, 2009
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    I was hoping for little fun project with the fab. I didnt think about the receiver part.

    I'm new and the stuff that srikes me are the little things. my first project was fixing an analog meter that should have just been thrown away. I did though!
    Found a burned diode and a cracked resistor.

    So who knows maybe adding a little coil or a wire. i'm just talking out my "noobie" arse!
     
  15. bigcape

    Thread Starter Member

    Sep 18, 2009
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    Circumvent laws??? You have got to be kidding me! I had no such intent!

    Have a cup of coffee John- please!
     
    Last edited: Oct 13, 2009
  16. bigcape

    Thread Starter Member

    Sep 18, 2009
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    I AM DONE WITH THIS THREAD> I WILL NOT BE RESPONDING ANY MORE!

    There is something really wrong with some of you folks!
     
  17. jpanhalt

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    Jan 18, 2008
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    No, I was not. Messing with the FCC is serious business. Interference with others who use the radio spectrum is serious and can cause loss of property, personal harm, and even death.

    Just what do you mean by that?

    John
     
  18. bigcape

    Thread Starter Member

    Sep 18, 2009
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    Now thats what Im talkin about! You and I could "hang out" !!:D
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    It might seem "snippy" to bring up things such as FCC regulations, but we really do try to keep members within the FCC regulations. The FCC has absolutely no sense of humor if they think one of their regulations has been violated; they are known to throw people in the hoosegow and slap them with hefty fines ($10,000 per incident) for such violations. Tinkering with transmitters can get you in hot water that way.

    Receivers, on the other hand, just receive. All I can surmise is that the receiver for your remote keyfob is buried in the car someplace that makes the fob signal hard to get to. The obvious item that comes to mind is to re-orient the antenna for the receiver, or add a new one somehow. It's usually much more effective to improve the receiving antenna than boost the output power of the transmitter anyway.

    I have no clue were the fob receiver might be located in your car, or even what it might look like. "Somewhere in the dashboard" would be a likely place. But without a set of manuals, it could be pretty tough to track down.

    Then there's the matter of exactly WHICH frequency does the fob transmit on, or does it use spectrum hopping? I can't answer that question. Antennas are generally most efficient if they are tuned to the transmitter's frequency. So, I suggest that finding out where the receiver is located, and determining what the fobs' transmitter frequency or frequencies are would be a good start.
     
  20. wr8y

    Active Member

    Sep 16, 2008
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    I can. :cool: Give me 24 hours.

    I NEVER thought of this! I have two spectrum analyzers sitting in front of me, one goes to 1 gHz and the other to 50 gHz!!! I'll bring my fob in tomorrow and start looking.

    I'd just accepted this limitation, but Wookie's post has me thinking.

    Check back tomorrow, guys!
     
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