Lectrosonics FM875 User Manual download pdf (Page 8)

SYSTEM SETUP

This section includes some basic steps that will ensure trouble-free operation of your FM-AV4 system:

1) Make sure the transmitter battery is good, or better yet, new.

2) Charge up the battery pack in the FM875 fully before you use the system.

3) The internal antenna is built into the cabinet of the amplifier/speaker unit. Position the FM875 so that

it is not within 3 or 4 feet of large metal surfaces such as air conditioning ducts. It is also good practice

to position the unit so that there is a direct "line of sight" between the transmitter and the FM875.

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 along with the direct signal. If the

direct and reflected signals are out of phase with each other, as depicted in the figure below, a partial

or complete cancellation of the received signal will occur. The result will be a "drop out." A drop out

sounds like either a hum or 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. Moving the transmitter even a few inches

may change the sound of the hum or hiss, or eliminate it. A dropout situation may become either better

or worse as the crowd fills or leaves the room.

In the event that you do encounter a dropout problem, first try moving the FM875 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 FM875 to an entirely different location in the room.

REFLECTIVE SURFACE

DIRECT SIGNAL

INDIRECT SIGNAL

TRANSMITTER

RECEIVER

PHASE

CANCELLATION

MULTI-PATH DROPOUT

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 17 18

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Lectrosonics FM875 User Manual Page 8