Introduction: Fixing a Car Alarm Remote Antenna.

Picture of 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.

Step 1: Opening the Remote.

Picture of Opening the Remote.

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

Step 2: The Rf Board.

Picture of 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.

Picture of 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.

Picture of Connection of the New Antenna.

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

Step 5: Reassembly!

Picture of 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/

Comments

tomasina (author)2016-09-23

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.

Mjtrinihobby (author)tomasina2016-09-23

Well those are usually only Good for car alarm applications.

andrewty (author)2015-12-18

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?

Mjtrinihobby (author)andrewty2015-12-18

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.

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