I’m sure right now you are thinking that I’ve lost it and am about to delve into the occult. Never worry, my friends I don’t do occult. This is a piece about loud radio stations. Hmmmm. Come to think about it, maintaining high audio levels was almost a cult in AM radio broadcasting back in the day. The broadcaster’s obsession with maintaining high sound levels was driven by the way AM radio works.
Excuse me for a minute while I explain: an AM transmitter without any sound coming through it transmits a steady “carrier wave” or “carrier”. If you tuned into a station that was broadcasting silence, you would hear a lack of the background noise that is everywhere on the AM band. The sound signal coming from the audio mixer console operated by the DJ is used to “modulate” the station’s carrier. That is the carrier signal is turned up and down in such a way that matches the sound signal from the control room. Your AM radio receiver converts these changes level or amplitude of the carrier back into sounds that it sends to its speakers. This is called Amplitude Modulation of AM. OK – enough of the geek talk, the basic idea is that the louder the sound coming into the transmitter the better you can hear the station. Louder stations can be heard farther away than quieter stations operating at the same. So the holy grail of the AM station operator was to maintain has high a loudness as possible.
However there was a point where the station got so loud that the carrier was actually being cut off and on by the loudest peaks of the sound. This point was called 100% modulation. Legally you could not go past that point. Going past 100% modulation creates distortion in the receiver and could get you a nice fine from the FCC. This meant that you wanted to compress the sound signal as close as you could to that 100% level. By the way, FM or Frequency Modulation radio works differently. Don’t worry, I am not even going there.
So, back in the day, man and machine worked together to make the AM radio station as loud as possible. The DJ would adjust the sound level to read zero Volume Units (VU) on the VU meter on the mixing console. His or her goal was to keep that meter as close to 0 VU or 100% as possible without going into the red zone of the meter. This was an art form as well as a skill; when mixing two sources of sound, such as an announcer’s voice and the that is playing under the announcement, the outgoing sound is combined as the sum of both. So when a DJ is starting to announce, the sound level of the music must be reduced to keep the sum of the two from going over 100%. Through experience, the amount that the music must be turned down becomes part of the DJ’s muscle memory, automatic. A good DJ can maintain the audio level between 85% and 100% most of the time. That was the goal! I know of some program directors who told their DJs that they had better not catch the VU meter outside that 15% range any time they walk into the control room. Needless to say, that is almost impossible.
This is where the machines come in. The one we had at WCOS was a classic; the Gates Level Devil! This tube driven monstrosity was a DJ’s bosom buddy. Our engineers kept our Level Devil tweaked up so tightly that given some really unusual thing happening, it never let the station get above 98% modulation. And I swear that silence or “dead air” was maintained at 75% modulation somehow. I never saw that transmitter output level remote display drop below that level. If course I never gave it chance to do that either because “dear air” usually garnered an uncomfortable call from the program director about keeping the station moving along. Yes – program directors were usually pretty crotchety because they never slept for keeping an ear open to what was on the air. That was their job, and all of mine did it well.
One night my buddy Scotty Quick and I were in the studio late at night. Scotty was giving me a friendly hard time because every time someone took a picture of me at the console, the VU meter came out at 100%. He wasn’t so lucky in that he didn’t seem to be able to get a picture with the meter over 70%. Trust me, I didn’t have any magic skill that he lacked, it was the luck of the draw. This got us into a discussion of how good the level devil was. And eventually we decided to test it. So I blew up a paper bag, turned the microphone on in the middle of a song and popped the bag. The result was silence, not just dead air, but we were off the air. OMG, we both dove for the remote control and put the station back on the air. Unbeknownst to us, the chief engineer was at the transmitter site and immediately the phone on the remote control unit rang and he asked; “Just what in the heck did we thing we were doing?” When we sheepishly told him he was lost in laughter for about 30 seconds before explaining to us that we had managed to drive the transmitter to about 150% modulation, and that the transmitter’s safeties kicked in to protect the final tubes. So we promised never to do that again in exchange for his agreement never to tell management that they had a pair of “out of control idjits” working for them. Hey, what can I say, I was only 20 at the time.
Later in life, as I transitioned from on the air to engineering and I looked at the part time staff of the stations I worked for, I remembered my own experiments and I decided to make sure they couldn’t repeat my experiment, I build in a hard limiting circuit that would not let anything over 125% modulation through, ever! Sure enough, a couple of weeks later, late at night as I was driving home one night, right in the middle of a song, there it was “BANG!” But the station kept right on going once the compressor recovered from the shock. There was a phone booth at the corner of the next block, and I made the same deal with them that my old engineer made with me. What goes around comes around. Oh MY!