I purchased the Belkin Bluetooth Music Receiver F8Z492-P so I could play my iPhone through my stereo wirelessly. I was very disapointed with the range of the bluetooth on the device (10-15ft) and did this simple hack to double it’s range. Now I am getting 30-40ft in range out of this little device by just removing a metal weight that sit’s inside of the bottom of the device.  Enjoy!