Fixing a Car Alarm Remote Antenna.

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.

Supplies:

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

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    tomasina

    2 years ago

    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
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    Mjtrinihobbytomasina

    Reply 2 years ago

    Well those are usually only Good for car alarm applications.

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    andrewty

    3 years ago

    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
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    Mjtrinihobbyandrewty

    Reply 3 years ago

    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.