|Wireless Microphone Systems from Sound Advice|
Are you concerned about finding a wireless microphone system what works on a
consistent basis for a reasonable cost? Do you avoid using the
wireless microphone because of some "war stories" about stray interference
during a service or presentation? Maybe you've heard of interference
caused by CB'ers, fluorescent light ballasts, car engines, cordless phones
or garage door openers. Maybe you've asked yourself "how far away can
I be from the receiver without losing the signal? Can I find an
economical wireless system that is also reliable? If so, what features
should I look for in that system?"
There are three frequency bands which wireless microphone bands operate on. They are Lo band VHF (25-50 mHz and 72-76 mHz), Hi band VHF (150-216 mHx), and UHF (450-488 mHz and 902-952 mHz). Lo bands have a definite cost advantage, but they are also much more susceptible to interference from cordless phones, toys, garage door openers, and occasional interference from sources a long way away due to atmospheric conditions. UHF is of high quality and comes with a higher price, although prices are becoming increasingly more affordable. For this discussion we will concentrate on the Hi band VHF systems.
Should the system have a compander? Yes--without compressor/expander circuitry most wireless systems are limited to a signal to noise ratio and dynamic range of 50 dB. Companders extend these specifications to exceed 80 dB or better. A system without a compander should not be considered for most professional applications.
Do you need diversity operation and more than one receiving antenna? It depends.
Answer #1: If the
operating distances between the transmitter and the receiver are short,
single antenna operation will likely be fine. The structure of the
building is very important. If there is very little metal to reflect
the radio waves, then a single antenna will probably work very well at
normal distances in churches or schools.
A "signal dropout" can occur at any operating distance and is caused by the direct signal from the transmitter (called multi-path) arriving at the single receiving antenna out of phase. For example, you are listening to the FM radio in your car, pull up to a stoplight and all of a sudden, the signal "swooshes" and drops to a very low noisy level. You're at a dropout location--the antenna on your car has picked up both direct and reflected signals at once. If you pull up a few feet your car will come out of the dropout area and receive normally.
The solution to this problem is to use two antennas (diversity) at different locations. Within the receiver, some manufacturers use two separate receivers, and switch to the receiver with the best signal.
Another system is the mixed/phase related diversity system. This is a reliable system where two antennas are used on one receiver. The internal diversity circuit monitors the overall antenna performance. If signals arriving from the transmitter happen to be heading toward an "out of phase" condition, which would normally result in a fade or noise-up, that phase difference between the two antennas is modified until the signals add in phase. The system is noiseless and extremely effective at a reasonable cost.
How to Install a Wireless System
Common Wireless System Problems
Shattered crystals or component failure are seldom the culprits in wireless microphone failures. More often than not the problem lies with