More than 5 years ago I bought a cheap Bolun WR-601 wireless lavalier microphone for playing around with my camcorder and proper audio for example at presentations. I totally forgot about it till yesterday since I never had used it before. Short tests at home with an old netbook as recording device were promising. But then when needing it at a seminar - which was close to train rails and the mandatory radio distortions close to the power lines-, I couldn't use it as reception was limited to one or two meters. The sound captured by the Samsung HMX-H200 camera itself is still usable, but you have this usual thin, distant 'speaker in a huge room' sound.
So the receiver of the Bolun WR-601 needed a better antenna. Since it uses fm frequency, I removed the socket from a cheap, small TMC antenna for GPS navigators (these are dirt cheap on eBay and look like this.). It is more or less a wound up long wire antenna with good reception properties. I soldered one end of a small piece of silver wire to it, the other end to the antenna solder point which is used on the PCB. Fixed it with a small drop of hot glue and made the antenna hole in the other case side bigger. After closing it, it needs even more hot glue to be stable and more sturdy.
The first test showed outstanding success. I went more than 5m away into the kitchen, so the signal had to go through walls - and no distortion was added! This seems to be a must-do modification so this cheap lavalier mic works as intended. A short test capture shows success while walking through the house: Test MP3.