ClearOne WS800 Manuale di applicazione - Pagina 7

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Appendix

(1) Intermodulation Distortion Interference (IMD)

Two or more transmitters operating in close proximity produce low-level, side-band frequencies called IMD.

These sideband frequencies can interfere with other microphones that normally operate on the same side-band

frequencies, but only when the IMD signal strength is comparable to the transmitter's signal strength. This can

happen when the interfering transmitters are in close proximity to the antennas while the interfered transmitter is

far away.

Case III - D above is a typical example. Microphones four

feet away from the antennas on stage left will have a signal

(and corresponding IMD) that is 64 times greater than the

signal from a transmitter that is 32 feet away on stage right

by the inverse-square law. In this case, the IMD signal will

cause dropouts and hits.

The science of IMD control is to arrange the antennas so

that all of the transmitters are about the same distance

away from an extension antenna. A good rule of thumb

is to divide the distance between the transmitters located

closest to an antenna and farthest from an antenna. The

result should be a number between 1 and 2. It may seem

counter-intuitive to move the antennas away from the

performance area to reduce dropouts, but Case III C will

have less IMD interference than Case III D.

In addition, ClearOne's digital wireless transmission

method uses numerical techniques that make them far

less prone to IMD interference than is possible with analog

systems. That is one reason ClearOne's arrays can be

much larger than is possible with analog systems.

(2) Diversity

Transmitter antennas radiate power in a toroid-shaped (donut) pattern. Very little energy radiates out the ends of

the transmitters. Separate the antennas sufficiently so at least one receives a strong signal.

(3) Dipole Antennas:

ClearOne systems are shipped with dipole (rabbit ear) antennas, but they are only recommended with small

systems and only when they are in the line of sight. They provide only a minimal diversity.

ClearOne recommends extension antennas whenever possible.

(4) Free Antenna Design:

ClearOne offers complete antenna hardware kits custom made for your project. The kits include extension

antennas, tested antenna cables with proper terminations, and antenna combiners if required. The goal of

extension antenna kits is to take all of the guesswork out of one of the most challenging and critical aspects of a

wireless microphone installation so your job is completed on time and within budget.