Shure ANTENNA SETUP Manual page 9

Coaxial antenna cable loss at VHF and UHF frequencies
per 100 ft (30 m). Use this value to calculate the expected
loss at the receiver for the desired cable run. A loss of
between 3 and 5 dB of signal strength is considered
acceptable. If the cable run results in a loss of greater
than 5 dB, active antenna amplifiers must be used to
compensate in order to avoid poor RF performance. These
active amplifiers may provide a selectable amount of gain.
Power for these amplifiers is drawn from the receiver's
antenna inputs or the antenna distribution system. (Note:
Not all wireless microphone receivers have this voltage
present. Please consult the specifications ahead of time.)
The appropriate gain setting is determined by the loss in
the cable run. The amplifier is placed at the antenna, and
Remote antenna amplifier
band-specific, available as both narrow or wideband.
Each connection between two sections of cable may result
in some additional signal loss, depending on the connector.
To increase reliability, use one continuous length of cable
to go from the antenna to the receiver. If antenna amplifiers
are being used, mount the antenna directly on the input
of the first amplifier, use one length of cable to go from
the amplifier to the second antenna amplifier (if needed),
and from the second antenna amplifier to the receiver.
can usually be wall-mounted
or stand-mounted. In extreme
cases, two amplifiers can
sometimes be connected in-
line to achieve longer lengths.
Make certain the receiver or
antenna distribution system
can supply enough current
to power multiple antenna
amplifiers. Finally, as with active
distribution systems, realize
that antenna amplifiers are also
Wireless Systems Guide for
ANTENNA SETUP
Antenna amplifiers
Hint: Do not over-amplify the radio signal!
More is certainly not better in this case. Excess
amplification can overload the front-end of the
receiver, causing drop-outs and RF "bleed"
(one transmitter showing up on several
receivers) on an antenna distribution system.
Try to use only the amount of gain necessary to
compensate for loss in the cable. Net gain
should be less than 10 dB.
Summary:
• Always use 1/2-wave or directional
antennas for remote mounting.
• Use the proper low loss cable for the
installation.
• Use the required antenna amplifiers
to compensate for cable loss.
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