Fixing a Car Alarm Remote Antenna.

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Introduction: Fixing a Car Alarm Remote Antenna.

About: Update 12 September 2017: A very special thanks to Sam Elder, a manager here at Instructables, who tracked down the cause of my lost publications and fixed the issue. Take a bow Sam!

Here is my viper remote. It's old and the original antenna was damaged and replaced by a simple wire. The range with the wire is limited to about 80ft line of sight.

I wanted to replace this wire with an antenna suitable for the 433mhz frequency the remote uses.

Step 1: Opening the Remote.

Getting open this old 2 way remote was easy. Now I have access to the circuitry.

Step 2: The Rf Board.

This rf board slots into the bigger board that contains the lcd display. You can see the antenna connection.

Step 3: The Replacement Antenna.

Here it is. Nothing fancy but a spring of correct length for the frequency band. Using my Tools I bent the end out to allow soldering onto the circuit board.

Step 4: Connection of the New Antenna.

Quick easy solder and the antenna is now on the board.

Step 5: Reassembly!

Using a plastic cable Tie, my old remote is reassembled. Now my range is around 800ft line of sight and I'm very happy.
Not bad for a 10 minutes job eh?

Update:

I made the antenna pretty afterwards in this instructable;

https://www.instructables.com/id/Covering-a-Spring-Antenna/

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    4 Discussions

    nice ible. thx for the idea using a spring to boost antenna.
    want to pick your brain.
    have you any ideas for re- purposing the alarm antenna?
    I just junked my 2nd hand car. the antenna was stuck to my windshield
    never knew what it was for.....so I pulled it off before they picked up the car.

    1 reply

    Well those are usually only Good for car alarm applications.

    Can you show how to work out the coil length for your frequency?

    Are all remotes for cars at the same frequencies, of around 433MHz?

    1 reply

    I just researched online and some helical antennas for 433Mhz were 35mm long which is the same length as the spring I used. Yup the vast majority of key fob RF remotes use 433Mhz. In the end the spring length can vary +/-5mm since this is not mission critical equipment at work. If you were flying a toy aircraft then for sure you need proper spec antenna. I'm extremely happy with the new extended range I'm getting.