Local Radio Station Closed Down

The signal of local "community radio station" on 87,9 MHz has disappeared today, on the 6th of November 2007. The transmitter was on the air continuously almost eight weeks at least since the 14th of September when it's existence was discovered. The radius of it's coverage area was about 400 meters. It broadcasted in stereo and it's programme content was mainly just "empty" carrier. However, the signal had strong mains hum. When talked about real broadcasted audio, MSN Messenger sounds were often heard on the frequency - couple of times also music and sound track of some TV programme.

Of cource, we are now talking here about now-legal 50 nanowatts minitransmitters whose nominal radius of coverage area is around 5 meters. That figure refers to good quality stereo signal but one can easily imagine that these can be heard from much further distance with weaker signals. We must keep in mind that on a free channel the signal just above the noise level can be very listenable, readable as we can say. In this case, the distance to the transmitter was approximately 200 meters and the tuner showed 10-28 dB signal strength at different times. Triax 3-el. Yagi was the receiving antenna.

What was unusual here was the fact that this minitransmitter was on the air continuously almost eight weeks. It was connected to the mains judging by the strong mains hum audible all the time. But as stated there was something wrong with the connection because the mains hum was so loud. These little devices are usually battery operated to eliminate the humming problem.

These minitransmitters can be a real threat to FMDX-ing if used on a "wrong" frequency and if several equipment are used in a relatively small area. In this particular case, the Sporadic E season 2007 is now over and no potential tropospheric targets is on the frequency in question, so this community broadcaster was rather harmless. The situation would be totally different during the summer months...