Grey wire mod (extend alarm remote range)

[vegas]

Your Toyota remote works at a frequency of 303.875 Mhz

If this is true, then a one-wire antenna length can be calculated by 300/303.875 = .9872 meters or 98.72 cm in length. I would bet cutting a wire to 1.1 meters and running it up the B pillar and across the top of the DS door would be just fine. Start at 1.1 meters and trim off a couple centimeters each time testing for range until it starts to get less and stop.

Another thing to try would be to grab a piece of coax cabling like the stuff used for cable TV. Cut a length long enough to get to the B pillar and above the bottom of the window PLUS the 1 meter for the antenna. If you solder the shielding to the ground on the alarm unit and replace the gray wire with the center wire in the coax, then strip all of the insulation and shielding down to just the bare center wire starting above the bottom of the DS window and then run the wire up the B pillar and along the top of the DS door and down the A pillar you'd probably maximize reception. The shielded/grounded coax section acts as a wave guide for the received radio signal. The bare center wire is the antenna part. Doing things this way means the entire antenna is above the bulk of the metal door skin and only has the pillars and roof skin attenuating the signal. I would bet that the resulting range would be HUGE with this setup.

I'm going to try it out on my LX this weekend.

 

[vegas]

Confirmed. FCC ID on my LX fob is: BAB237131-032

The information from the FCC says that the frequency is: 303.875 MHz

 

[vegas]

So I finally got around to trying this approach out and it works fantastically well. I'm calling this the coax wave guide ultimate gray wire mod.

I took pictures:

01 strip 5 cm of coax and make the shielding into a wire by twisting

• vegas
• Jan 15, 2020

02 shrink tube to keep things tidy

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03 add connectors and final shrink tube to give strength

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04 measuring the overall length

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05 positioning the bottom of the antenna

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06 figure out where to start stripping to make the antenna

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07 close up the junction with shrink tubing

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08 start tucking the wire at the stripped to unstripped junction

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09 starting to tuck the antenna wire

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10 position the unstripped to stripped junction here

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11 putting the exposed antenna in the rubber trim

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12 connect the ground to lower left, antenna to upper right

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13 all buttoned up

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14 mix a drink and lock/unlock your truck from inside the house

• vegas
• Jan 15, 2020

The end result is that I can lock and unlock my LX450 from about 100 feet away. So why does this work so well? It's a couple of things that take advantage of electromagnetic physics to do everything right for radio.

First of all, by using coax cable and grounding the shielding, I have created what is called a "waveguide". It means that the antenna doesn't actually start until the center wire of the coax exits the shielded section. This effectively allows me to move the start of the antenna across the floor and up the DS B pillar to the level of the window. That gets the whole antenna out from behind the door skin. At that point I strip off the outer cover, cut through the braided shielding and the insulator material and stripped everything off leaving the bare copper wire. That's the actual antenna.

Secondly, the antenna is a solid copper wire. Solid wire antennas always perform better than braided or multi-strand copper wire antenna for reasons I'm not going to explain. Just chalk it up to "physics" and know that solid wire antennas are always better. It is important to note that the factree 'tenna is a pitiful twisted copper wire hiding behind as much body steel as possible. That is precisely why the reception sucks; again, physics.

Thirdly, the stripped antenna part is about 1 m in length. This is the ideal length for a one-wire antenna tuned to the frequency of the key fob radio transmitter (see my previous post, to posts back). Radio reception is best when the radio waves induce resonance along the wire antenna. The length of wire antenna matters most. Again, more physics; use an online calculator to calculate ideal length from frequency.

Lastly, the antenna part is tucked into the rubber edge cap all the way up the DS B pillar and then forward along the top of the door and down to about the top of the DS "oh sh*t" handle. This exposes the antenna to the outside as much as possible and minimizes the amount of steel between the fob and the antenna. Ideally the antenna wire would be kept straight to maximize its sensitivity but this is a curvy truck, the wire had to curve. Less than ideal, but not by much.

By combining all of these tricks of physics I have a highly tuned, highly sensitive, well placed antenna for receiving the pitiful puffs of radio that the key fob puts out. Like I said, my range is around 100 feet. Maybe we need to make this into a contest and give prizes at the next cruiser crawl for whomever can unlock their 80 series from the farthest distance using a stock fob and stock alarm unit.

NOTE: The last step in this tutorial is crucial to success. I made myself a drink called Churchill's Breakfast and laughed as I locked and unlocked my truck from inside the house.

Happy truck tinkering!

 

[george_tlc]

Tuned for the exact frequency of the remote I presume? Pity that the factory antenna output isn't an RF connector to mate to the coax...

Of course putting the 'antenna' right up against the metal work of the door frame does kinda/sorta detune things

Anyhow, I just extended the wire from the original piece of wire up around the headrest. Easily get several hundred feet. I'm using an aftermarket remote - but did tune its center frequency with a spectrum analyzer though

cheers,
george.

 

[vegas]

Tuned for the exact frequency of the remote I presume?

Yup, see my two posts prior to my write up.

Of course putting the 'antenna' right up against the metal work of the door frame does kinda/sorta detune things

Sort of. To do it right there's a minimum gap between the antenna wire and the body steel to maintain but if you don't you only lose a few tenths of a dB. Probably translates to losing 20 feet in distance or so I would guess?

Anyhow, I just extended the wire from the original piece of wire up around the headrest. Easily get several hundred feet. I'm using an aftermarket remote - but did tune its center frequency with a spectrum analyzer though

Cheers mate, you win. Maybe the aftermarket fob has a stronger signal? Several hundred feet would win you the unlock trophy over my setup.

 

[george_tlc]

Yeah, it works a crazy long distance. Tuning the fob to be near on exact frequency makes a huge difference to range. The aftermarket fobs have a tuning trimmer cap. I'm guessing the factory one is crystal locked since there's no trimmer. Already have kids, so if the aftermarket one is cooking stuff - I'm already done with that stuff

cheers,
george.

 

[rolliges]

Incredible when one decent mod is improved into a great mod. Love this place.

 

[jonheld]

I like this a lot. I'm going to use a length of Belden 1855A. It's pretty thin and flexible, and I have lots of it.

So I finally got around to trying this approach out and it works fantastically well. I'm calling this the coax wave guide ultimate gray wire mod.

Where did you source the connectors? Part#?

 

[vegas]

I like this a lot. I'm going to use a length of Belden 1855A. It's pretty thin and flexible, and I have lots of it.

That should work too.

Where did you source the connectors? Part#?

I had some in my electronics parts bin in my shop. But I think they are these: Amazon product ASIN B07GGVJTB1

 

[tbo_cruiser]

Wow! I have owned my LX for over 10 years and spent a lot of time on this forum. But I just found this thread yesterday. Took me about 20 minutes (half of which was locating tools and wire). I didn't even remove the seat. Just moved in forward as far as it would go, and then reached in over the rs3000 and unplugged the 4 pin connector, reached in with some snips and cut the wire. Butt connected the new wire (close to the right wire and just looped it up around the head rest posts. Previously I practically had to stick the remote inside a window to get it to open. After install, I walked to my front door (red door in the background in the pic) and it locked and unlocked every time.

Then to boot, I discovered the thread on how to fix the automatic relocking because of malfunctioning door light switches.

This forum is AWESOME!!!