External Antenna for Sony Ericsson T715a Phone
Turn your phone into a transistor radio
Sony Ericsson T715a comes with a built in FM radio. I love this little phone. In order to use the radio, even if you intend to play through the speaker, you need to plug in the headset because the headset cable acts as an FM antenna. The phone won't even play the audio through the speaker if it detects that the headset is not plugged in. That bothered me so I built this antenna mod.
First you need to buy a very cheap adapter that converts the multipin connector to 3.5mm mini plug. In some cases that's possibly all you need. When you plug in the adapter the phone will be fooled thinking the headset is plugged in and will allow you to play the sound through the speaker.
However, the signal quality won't be great without an antenna so you need a piece of thick wire cut to about 40cm length (1/8th of the wavelength for the bottom of the FM dial). Simply solder the wire to either a stereo or mono mini plug. I used a stereo plug and it seemed that any of the three connectors produced equally good static-free sound. I was just careful not to soldier to more than one connector. Insert the mini connector into the adapter and you're good to go.