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Audio Tips
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| Antenna Overview for Wireless Mics Part 1 |
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| December 4, 2007 |
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Wireless microphones have come a long way in the past few years. Battery life, robust construction, ease of use, and reliability have all been driving factors in their popularity.
Often, when operators receive their wireless mics, they hook them up, set the frequencies, and move forward. In most cases that’s fine. However there are some finer points that can enhance their overall performance. Antenna selection, proper mounting, and placement can certainly affect the overall performance, even with modern diversity units.
First of all, the length of an antenna is directly associated with the frequency at which it will be operating. Usually, for wireless mic applications, the antennas will be either quarter-wavelength or half-wavelength. For reference, a 400 MHz wave has a length of about three feet. A half-wavelength would be about 1.5 feet, while a quarter-wavelength would be about .75 feet. Obviously, for ease of use, the shorter the better. The main point is that the antenna used for receiving should be properly matched to the frequencies being used. UHF antennas are notably shorter than their VHF counterparts.
Other types of antennas include unidirectional models, such as the log periodic or yagi design. Since the directional antennas are physically much larger by design, and are a little more “frequency-specific,” these antennas are used in special applications where the UHF band is employed.
When mounting the receiving antennas, quarter-wavelength models typically require a “ground plane” for optimum operation. This “ground plane” is usually a grounded (to receiver) metal reflective surface that is approximately the same size as the antenna in one dimension. Using a quarter-wavelength antenna is not recommended for remote mounting. A half-wavelength antenna is more suited for remote mounting as it does not require a ground plane.
In Part II, we’ll discuss additional antenna mounting techniques and tips for general equipment placement.
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