For the past few weeks, interference has been heard on 154.280, 154.265, 155.340 and a few other VHF public safety channels in the St. Louis area. Transmissions occur for only a few seconds making it hard to direction find. The interference sounds like it is off frequency and the audio can not be understood. It is not wide band and does not appear on all channels. Any help in locating the area or source through signal strength reports would be appreciated.