Lectrosonics R170 - Manual (Page 6)

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, a cancellation may occur. The result would be
a "drop out." A drop out sounds like either audible noise (hiss or hum as the transmitter is moved
around), or in severe cases, may result in a complete loss of the sound when the transmitter is
positioned in certain locations in the room. A dropout situation may be either better or worse as the
crowd fills and/or leaves the room, 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 the phase cancellation that results in a low RF signal 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 high sensitivity of the R170 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.
Position the antenna so that it is not touching or 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. In the event that you do encounter a dropout problem, first try moving
the receiver/antenna at least 3 or 4 feet from where it was. This may alleviate the dropout problem. If
dropouts are still a problem, try moving the receiver and/or the antenna to an entirely different location
in the room.
Lectrosonics transmitters radiate power very efficiently, and the receivers are very sensitive. This
reduces dropouts to an insignificant level. If, however, you do encounter dropouts frequently, call the
factory. There is probably a simple solution.
Figure 3 - Antenna Placement
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