8
FM +
Avoiding Hum in the Audio (as a Result of a Ground Loop)
A hum created by a ground loop can often be eliminated by connecting a capacitor in series with the audio line shield to the
transmitter’s ground. This method also maintains good radio frequency (RF) shielding. Determining the eectiveness of this
method for your installation usually requires some experimentation.
IN PHASE
1 2
3
3-PIN
CONNECTOR
BREAKING A GROUND LOOP WHEN
CONNECTING TO A UNBALANCED LINE
BREAKING A GROUND LOOP WHEN
CONNECTING TO A BALANCED LINE
.01 uF CERAMIC DISC
CAPACITOR
.01 uF CERAMIC
DISC CAPACITOR
Selecting an Audio Source Appropriate for Hearing Impaired Listeners
The FM + transmits audio with excellent fidelity. Therefore, the audio source signal should be of the highest audio quality and not
subject to a compressor, limiter, reverberation, or other signal processing equipment. While compressed audio is available through
the FM +, excessive compression is not helpful to the hearing impaired and can contribute to excessive noise in the audio.
The FM + audio source signal is usually connected to a mixer’s line output signal which is behind the mixer’s parametric equalizers
but ahead of any equalization used for house loudspeakers.
If audio delay is available for use in large auditoriums, it’s usually best to use it. Because radio signals travel faster than sound,
delaying the transmitted audio so that an average listener (in the middle of the listening area) hears the transmitted audio a few
milliseconds after audio from the main sound reinforcement system speaker is helpful. This will also help audience members who
lip read.
Installing the ANT 025 Whip Antenna
Gently thread the ANT 025 onto the stud recessed in the hole on the top of the transmitter.
0.75A
Streaming Audio Out
Ethernet
RoHS
Made in USA
Analog
Audio
Line OutLine / Mic In
phantom
bal
unbal
24VDC
RF75Ω Ant
REMOTE ANTENNA JACK
FOR 75 Ohm ANTENNAS
CHASSIS STUD
MOUNT
ANT 025 ANTENNA
(INCLUDED)
NOTE: If the FM + is going to be rack mounted, you will not be able to install the ANT 025 whip antenna. For rack mounting,
consider installing a remote antenna like the ANT 005 or ANT 024 - these antennas require using the Remote Antenna
Coaxial Jack (above) and a long length of terminated coaxial cable. Another option is to mount the antenna on the rack
itself - consider the ANT 029 which includes a 1RU bracket and a 3ft terminated coaxial cable.
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