Sunday, August 10, 2014

Static in the Headphones!

I don’t know what made me think about this. Maybe it is the stormy weekend we are enjoying. But, back in the 50’s and 60’s, when AM Rock ruled the airwaves, there was a FCC requirement that the operator of a radio station must constantly monitor the transmitter output. For most stations, this meant that there was a radio receiver located in the studio that was tuned to the station. This receiver fed the audio console operated by the disk jockey and was played on the studio speakers and the DJ’s headphones.

Why do DJ’s wear headphones anyway? Well, the quick and dirty answer is to prevent feedback, that awful squeal you hear when a live microphone is carried out in front of the speakers it is feeding. When a DJ turns the microphone on in a control room, the speakers are automatically muted to prevent feedback. The headphones are not cut off so the DJ can hear what is going on while the microphone is on.

So the DJ of a radio station back in the day was actually listening to the radio the same way you were at home or in your car. That means that he or she was listening to the entire audio chain from the record to the receiver. One of the byproducts of that is that if there was a thunderstorm in the area, you could hear the static from the nearby lightning in your headphones as well. To me that always seemed to make me “one with the station.” I became integrated with the turntables, cart machines, audio board, studio to transmitter link and the transmitter itself. I was part of the pulse of the station.

This feeling of “oneness” was particularly strong when there were storms in the area. Radio station towers were often struck by lightning. When that happened, an arc would cross the lightning arrestor near the bottom of the tower. The lightning arrestor consisted of two steel balls about two inches in diameter about three quarters of an inch apart. One of these balls was attached to the tower itself which was insulated from the ground. The other was attached directly to the ground. When lightning struck it would arc between these two balls rather than pass through the transmitter, causing damage, Over years of use, these balls would become pitted and ragged from the lightning strikes. As often as not, when this happened, the transmitter would be knocked off the air. The DJ would have to restart the transmitter by pushing the “plate on” switch on the transmitter face or the remote control. I can remember many a summer night doing my show with one hand poised near that switch, bringing the station back to life several times in a minute. It was me against the storm, and I was bound to not let the storm win the battle of wills. There were a few times when the storm won by striking so hard that the power to the transmitter was interrupted. When that happened I needed to go through the entire start sequence for the transmitter that needed at least a minute from beginning to end.

Today’s radio DJs don’t listen to the transmitter output. That rule was placed in the annals of history a long time ago by the FCC. These days, the DJ listens to the output of the audio console. So even if the station were to go off the air, he or she would not now it immediately. This works for modern times because what you hear on the radio is usually somewhere between 7 and 20 seconds behind what the DJ hears. This is because most digital FM transmitters take about 7 second to convert the input signal to the analog and digital signals that they transmit. Add to that the 10 second delay that is intentionally inserted that allows to DJ to “dump” any content that inadvertently gets by the operator. This delay is most used in live call-in talk shows.

Most “Old School DJs” really miss not being able to hear themselves on the air. The thing they cannot hear is the processing that is done to the signal before it is sent to the transmitter. This processing usually consists of two things, the first being dynamic range compression, also called audio level compression, in which the dynamic range, the difference between loud and quiet, of an audio waveform is reduced. The other thing is equalization, commonly used to alter the frequency response of an audio system using linear filters. When the DJ is listening to a receiver, he or she hears this processing. When listening to the output of the audio console, they can’t hear the processing. This is so important to so many DJs that many stations install two sets of processors set up identically, one feeding the transmitter and the other feeding the studio monitors and DJ headphones. In addition to having happier DJs these stations also have a stand by ready to be switched over in the event that one of the on air processors fails.

When I look back over the years, some of the fondest memories I have are of being on the air on one of the AM stations for which I worked, sitting back in the air chair with my hands behind my neck and my eyed closed for a few moments enjoying a record complete with the compressors, equalizers and of course, the static! Now that was real radio. Oh MY!

No comments:

Post a Comment