Make a Mobile Antenna to Listen to FM Radio Without Headphones




Introduction: Make a Mobile Antenna to Listen to FM Radio Without Headphones

Listening to FM Radio on our Mobile Phones Always needs headphones. And especially indoors, the reception can be quite bad. So here's how to build a Simple Antenna to listen to radio without headphones. As a benefit, they also greatly improve reception indoors.

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Step 1: Get the Materials

You will need:

  • An old/cheap antenna (I got one from my old toy RC Plane remote)
  • An old pair of headphones/Aux Cable (To get the .35 mm jack)
  • A pair of scissors
  • Scotch Tape (Also called Duct tape, Transparent tape, etc)
  • A phone which supports listening to radio

Step 2: Strip the Headphone Wire

Now you need to strip the headphone wire to a little bit away from the jack. You can do that with your hands or with a scissor.

Step 3: Cut the Jack Along With the Stripped Wires

Cut the jack from the headphone leaving some of the wires you stripped earlier.Make sure the Copper is exposed properly.

Step 4: Insert the Jack in the Antenna

Depending upon the radius of the antenna, you may have to thin the outside black part of the jack and insert it straight into the antenna as in the picture. I have used an expandable antenna. You also have to be careful that the copper wire touches the edge of the antenna. For that, just fold the Copper wire towards an edge and push it in the antenna. It doesn't matter if it touches or not, but indoor reception has been great for me if it touches.

Step 5: Put Some Tape Over It and Put It Into the Phone!

You can see in the image that the radio doesn't work without headphones, but as soon as I plug in the antenna, it thinks of it to be a headphone. Also, you must select the speaker mode to get the sound out of the phone speakers. Look here and there, it's pretty easy to find.

Step 6: Done! Just a Notice for Sony Xperia Users

For All Sony Xperia Users, you must cut the headphones that came along with your phone. Otherwise, it won't work.

This is my first inscrutable, so forgive me if something is not up to the mark. Hope You Liked It!!!

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8 Discussions


3 years ago

I don't know where to start. I have to point out though that I will try to be as informative as possible in my comments.

First off, a vast majority if not all mobile phone audio outputs are powered by chip(CMOS) type amplifiers that operate with an output impedance of 16-32ohms. If you short left and right connections(red and white wires) to ground(bare wire) you are putting the output impedance to 0ohms and therefore making current infinity amperes thus frying the chip. I can tell you with absolute certainty that when you put your phone to max volume, plug that antenna(with wires twisted, shorted and touching the metal part) you will damage the amplifier IC. Try removing the antenna and plug a normal headphone in and you will notice a significant drop in the max volume or no sound at all!

Second, your mobile phone, whatever model it is, will detect types of connection depending on the impedance it is sensing on your headphone jack. that's how your phone knows which icon to show a headphone icon with a mic or no mic. This is done via sensing the fourth wire(forgot the color, might be green or yellow) whether there is impedance or if it is simply grounded. Shorting the mic(4th wire) wire to the ground will not damage the preamp circuit as this is similar to a silent mic. Inversely, audio out(red and white) senses presence of connection as impedance >threshold ohms =no connection, impedance < 32 ohms = headphones, impedance < 32 ohms + 4th wire not equals 0ohm = headphones with mic.

Third, this project works to bypass the fm radio requirement as a shorted connection from audio left and right to ground)white and red to bare) where the mobile phone senses the "headphones" simply because impedance dipped below 32ohms which is actually 0ohms since it is shorted to ground.

4th, i can almost guarantee that you will no longer be able to use your headphones satisfactorily. Since phones by default will run audio to headphones(that are grounded by the antenna) and fry the chip before you can set it to play via loudspeaker.

5th, what you can do is buy 2 pieces of 16ohm resistor rated at 1/2 watt, connect one end of one to the red wire and one end of the other resistor to the white wire and connect both loose ends to the bare copper. this will fool your cellphone in to thinking it is plugged to a set of headphones but the resistors will limit the current and help to avoid frying the amplifier IC. Even without the telescopic antenna it will pick up radio waves and your radio app will work although reception won't be that good. You can put the whole assembly inside the telescope if you want to boost signal but make sure the white and red connections of the resistor is insulated and does not touch the insides of the metal. Put your phone on the lowest audible volume setting before you plug it in so you don't run the risk of overheating the resistors. Please note that this is in theory and you do this at your own risk!

Please note that my comments are not out of spite but to help you avoid costly repairs from a fried audio chip especially on waterproof xperia phones as waterproofing from a repair is an added cost. This is backed by my experience in Electronics Engineering and actually making the stupid mistake of shorting left wire to the ground during one of my audio amplifier experiments where i used my nokia 5300(college days) as an audio source. Damaged the left side headphone output and no longer worked at 100%. When volume at full, right outputs at full but left outputs only at about 10-20%. Barely audible.

Last words: It is a good way of educating yourself by making mistakes and learning from them and continuing to develop your theories but it is never a good idea to spend too much on it. Especially as a student. Learn as much theory as you can(books are a good source as well) from the internet before trying it out on actual objects that might cost you a small fortune. And if you are not 100% sure, or even if you are, always include a disclaimer("do this at your own risk" types of messages) in your ible so that you can avoid negative comments.



Reply 3 years ago

I'm not specialist, but I have a question: does the antena act like a proper rezistor?


Reply 1 year ago

The antenna doesn't act as a proper resistor. B.T.W You could build an adapter with both an FM-antenna, and headphone outputs.

Adarsh p
Adarsh p

4 years ago

Good WoRk Man... i love It


5 years ago on Introduction

An interesting project!

It's not a good idea to "short circuit" all the wires in the headphone connector (might damage the phone's circuitry) but might be better to find out which one actually acts as an antenna and only connect that one to the external antenna. Of course that isn't easy with such thin wires.