A history lesson: when Shure introduced the Vagabond professional wireless mic system in 1953, its primary purpose was to replace the 20 foot cable attached to the microphone. The Vagabond was not expected to reliably transmit a signal for hundreds of feet. In the 1970s, wireless mics began to grow in popularity, particularly for in-studio TV production (think "person presenting the weather") and for Las Vegas stage shows. But even then, the transmission distance was relatively short.

As wireless mic technology improved, the transmission distances increased. Eventually, the pro audio world began to think of a wireless mic as replacing a 200 foot cable run, not just a 20 foot mic cable. So antennas were moved farther away from the stage - often ending up by the mixing console for the sake of convenience. This antenna relocation method worked well for three decades, primarily because there just were not many RF (Radio Frequency) signals in the air.

But now in 2013, the trend is beginning to reverse. The reason is the...

...ever increasing level of RF background noise from new digital TV stations, new smartphones, new Wi-Fi hot spots, new wireless signage, etc. This high level of RF background noise can (and does) interfere with the reliable operation of wireless mics and wireless in-ear systems.

One method to combat the increasing RF background noise is to locate the antennas closer to the stage. If a UHF antenna is placed 20 feet away from a hand held transmitter, instead of 200 feet, the signal can be up to 20 dB stronger. (20 dB = a factor of 100!) In other words, the signal received by the antenna is 100 times stronger at the 20 foot distance, and this can often overcome the increase in RF background noise.

Some of you are thinking, "What about the loss of signal over the long run of antenna cable?" Well, 200 feet of RG213U cable will attenuate the signal by about 12 dB.

Even with the cable loss the receiver is delivered 8 dB of additional RF signal: +20dB - 12 dB = +8 dB.

Another method is to place the receiver with the antennas near the stage, then run the low impedance balanced audio signal back to the mixing board via a cable or cable snake. Low impedance balanced audio signals can be run over 1,000 feet with negligible signal loss.

For wireless mic antennas, like many things in life, closer is better.


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