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Increase range of key fob?

Discussion in 'Gen 3 Prius Accessories and Modifications' started by shaun5stu, May 31, 2011.

  1. shaun5stu

    shaun5stu Junior Member

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    I've got a Gen III Prius with the remote A/C start option and am wondering if there is a way to increase the range of the key fob? I work in Phoenix and have to park in the sun all day. My office is on the second floor of my building with a window overlooking the parking lot. I can see my car as I walk out. With summer approaching, I'd like to be able to point my fob at the car from my office, start the A/C, and have the car be somewhat cool by the time I walk down to it.

    I've done a little bit of preliminary internet searching and it seems the two most common methods of extending the range of fobs are to increase the antenna on 1) the key fob or 2) the car. I took my fob apart and didn't couldn't identify the antenna and didn't have luck looking up the IC numbers on google, so my next approach would be to try to extend the receiving antenna on the car. Does anyone know where this is located?
     
    #1 shaun5stu, May 31, 2011
  2. clintb

    clintb Clueless n00b

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    Put the fob up to your chin. End result: you are now an antenna.
     
    #2 clintb, May 31, 2011
  3. shaun5stu

    shaun5stu Junior Member

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    Yeah, tried that. Didn't work.
     
    #3 shaun5stu, May 31, 2011
  4. Judgeless

    Judgeless Senior Member

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    I had the exact same problem. When I ordered my Prius I ordered a Toyota OEM remote start that the dealer put in. I should have done more research. It does not give feedback, it does not work more than 30 feet, it only runs for 10 minutes without having to start the car again and you can only start the car twice.

    Your best bet is to take the lose on the Toyota remote start and buy a Viper Remote start system. You are looking at about $600 to have it installed or $300 if you do it yourself.

    My new system will start the car from up to 1 mile away or using my cell phone from anywhere in the world with internet access. It will run for up to 60 minutes and you can start it over and over. It will also let you keep the car running 60 minutes after you leave the car with the doors locked. I use this when I run into a store.
     
    #4 Judgeless, Jun 1, 2011
  5. shaun5stu

    shaun5stu Junior Member

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    Well, remote start isn't really what I need. My remote has an A/C button which will start the A/C only - not the car. (The Prius A/C runs off of battery, not the engine.) I did some tests yesterday and it looks like I've got a range of about 90 feet. I need a range of between 100 and 135 feet, depending on where I park. I tried using the bottom of a soda can as a makeshift parabolic reflector, but that didn't seem to increase the range at all.
     
    #5 shaun5stu, Jun 1, 2011
  6. Judgeless

    Judgeless Senior Member

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    The remote A/C funtion runs for a very little time period. A remote start system does the same thing as the A/C button but for a longer time.
     
    #6 Judgeless, Jun 1, 2011
  7. shaun5stu

    shaun5stu Junior Member

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    Correct. I just need the A/C to run for as long as it takes me to walk from my office, out the building, through the parking lot, to my car. About 3 minutes.
     
    #7 shaun5stu, Jun 1, 2011
  8. xs650

    xs650 Senior Member

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    You are close to having it work. Some E-Glass attenuates radio signals. Is there a fire escape you can walk out on so you don't have a window between you and the car?

    Most car remotes operate at frequencies between of 315 to 435 mHz. A parabolic reflector would need to be over 2 feet in diameter to be very effective at those frequencies.

    Can you park your car in different directions? A car remote's range varies depending on what direction you are from the car. You could find a big empty parking lot and walk around the car at about 130 feet to find out if there is one orientation that works better.

    Holding the remote to your chin also varies depending on the remote and how you hold it. I have had the best results holding the remote upside down and vertical. It has made a noticeable imporovement in range on any of the several cars I have tried it on. I think the reason for that is that you need to get the internal antenna as close to your chin as possible. The internal antenna is usually just a trace on the circuit board and not recognizable as an antenna unless you know how to figure out the circuit. I would need to get the spec sheet for the IC in the fob and might still have trouble figuring it out.
     
    #8 xs650, Jun 1, 2011
  9. Judgeless

    Judgeless Senior Member

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    This is how I start my car from work.

    [​IMG]
     
    #9 Judgeless, Jun 1, 2011
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