User guide

ANTENNA USE AND PLACEMENT

A wireless transmitter sends a radio signal out in all directions. Indoors, this signal will often bounce off nearby

walls, ceilings, etc. and a strong reflection can arrive at the receiver antenna along with the direct signal. Outdoors,

reflections can occur from nearby cars, trucks or metal buildings. If the direct and reflected signals are out of

phase with each other at the receiver antenna, a cancellation will occur. The result is a "drop-out." A drop-out

sounds like either audible noise (hiss), or in severe cases, may result in a complete loss of the carrier and the

sound. Moving the transmitter even a few inches will change the sound of the hum or hiss, or eliminate it. A drop-

out situation may be either better or worse as the crowd fills and/or leaves the room or the area, or when the

transmitter or receiver is operated in a different location.

The illustration below depicts a simplified multi-path dropout. This drawing is overly simplified to emphasize phase

cancellation at the receiver antenna. In actual use, there are numerous different paths that the radio signal can

take simultaneously, causing a multitude of different signals arriving at the receiver antenna. The resultant RF

signal level at the receiver antenna can be very low if there is significant phase cancellation. The high sensitivity of

the R185 minimizes dropouts in multi-path environments, since it will continue to operate with a usable audio signal

to noise ratio even with weak RF signal inputs.

In general, it is usually best to position the antenna so that it is not within 3 or 4 feet of large metal surfaces. If this

is not possible, try to position the antenna so that it is as far away from the metal surface as is practical. It is also

good to position the receiver so that there is a direct "line of sight" between the transmitter and the receiver

antenna. In situations where the operating range is less than about 50 feet, the antenna positioning is much less

critical.

Lectrosonics transmitters radiate power very efficiently, and the receivers are very sensitive. This reduces drop-

outs to an insignificant level. If, however, you do encounter drop-outs frequently, call the factory or consult your

dealer. There is probably a simple solution.

Figure 5 - Multi-Path Dropout