Impedance matched passive splitters (RF power dividers) will provide an even split of the available RF energy and relatively little will be lost to reflection. However, because the received RF energy is being divided up between multiple receivers, the signal level to all will be lower.

A two-way split will result in about a 3.5 dB loss, cutting range by about 30 percent. A four-way split will reduce range to about less than 50 percent of normal. This may be acceptable if the cable runs are short, but the combination of long cables and passive splitters may seriously degrade performance.

If splitters are truly required, active (amplified) splitters or multi-couplers can be used. Such units make up for splitter loss with the addition of an RF amplifier that boosts signal. However, the amplifier makes the unit more susceptible to intermodulation (intermod) and other forms of interference.

To reduce intermod, most units are designed for specific frequency ranges and tailored to specific types of receivers made by the same manufacturer. Attempts to use them for other frequency ranges will almost always result in extremely poor performance.

Good active splitters are relatively expensive because production quantities are low and parts cost is high. The fact that a high performance unit may cost nearly as much as a wireless system is very troubling to some users, who then turn to inexpensive passive substitutes or lower cost, but incompatible, units from another manufacturer. Because of the very real, and very serious, risk of interference, either use high performance units, or arrange the wireless systems so that active splitters are not required.

A regular contributor to ProSoundWeb Install Sound, Gary Stanfill is principle consultant for Colmar Systems, based in Southern California. His company has provided engineering and marketing consulting services to wireless microphone manufacturers for several years. Stanfill was president and general manager of Vega, a leading manufacturer of wireless microphone systems, for a total of 18 years. He has over 30 years experience in audio, RF technology, communications and wireless systems. He can be reached at gjstanfill@earthlink.net

For more articles by Gary, including a look at the potential impact that DTV will have on wireless systems, click here.