Lectrosonics R172 - Manual (Page 9)

ANTENNA USE AND PLACEMENT
Extend the antennas fully. Position the antennas so that they are not touching each other or within 3 or 4 feet of
large metal surfaces. It is also good practice to position the receiver so that there is a direct "line of sight" between
the transmitter and the receiver antenna. In the dual antenna mode, place the antennas at least 6 ft apart. If the
installation has two rooms serviced by the same receiver, you may want to extend one antenna into one room and
place the other antenna into the second room. See the illustration below.
A wireless transmitter sends a radio signal out in all directions. 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. 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 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 normally sounds like "hum" or "hiss."
Moving the transmitter (even a few inches) will change the hum or hiss, or eliminate it. A dropout situation may be
either better or worse as the crowd fills and/or leaves the room. The dual antenna configuration (passive diversity)
of the R172 helps reduce the probability of this problem occurring.
In the event that you do encounter a dropout problem, first try moving the receiver/antennas at least 3 or 4 feet from
where they were. This may alleviate the dropout problem. If dropouts are still a problem, try moving the receiver
and/or the antennas to an entirely different location in the room. Note - moving the receiver will only have an
effect if there is a telescoping whip antenna attached directly to the receiver. If both antennas are the coaxial
cable type, you will only need to move them around.
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