User's Manual

6 Applied Wireless, Inc.
Setting the Transmitter’s Audio Modulation Level
With an active audio source connected to the transmitter’s AUDIO INPUTS,
adjust the AUDIO LEVEL control on the front panel such that the green
MODULATION LEVEL OK indicator is illuminated whenever audio is present,
and the red PEAK indicator flashes only on the loudest audio transients. To
prevent distorted audio at the receiver, the red PEAK indicator should not
be illuminated continuously.
Note: The audio source device may have a volume control that adjusts the
level of the audio signal(s) being fed to the transmitter’s inputs. If your
source device (e.g. portable/personal CD player or MP3 player) is so
equipped, initially set that device’s volume control to its approximate
midpoint. Then, adjust the transmitter’s AUDIO LEVEL control as described
above. Use the following guidelines to “fine tune” the settings:
• If the audio output at the receiver suffers from excessive background
noise, the source device’s volume level is probably set too low.
Increase the source device’s volume control a bit, and readjust the
transmitter’s AUDIO LEVEL control accordingly.
• If the audio output at the receiver is distorted, and/or if the
transmitted audio program can be heard on (or interferes with) either
or both of the channels adjacent to the selected channel of operation,
the source device’s volume level is probably set too high. Reduce the
source device’s volume control a bit, and readjust the transmitter’s
AUDIO LEVEL control accordingly.
Adjusting Headphone Volume (Receiver)
If desired, stereo headphones or earbuds equipped with a standard 3.5mm
mini-phone plug may be used with the AR900-32 receiver. Insert the plug
into the HEADPHONE jack on the rear panel. The output level at this jack
may be adjusted using the VOLUME control on the front panel.
Note: The receiver’s VOLUME control only affects the volume at the
headphone jack. It does not affect the volume at the receiver’s line level
audio outputs.
User’s Guide – 900MHz Stereo Audio Transmitter & Receiver 11
Local/Distance (DX) Jumper (Receiver)
The AR900-32 receiver has an internal jumper that determines the
receiver’s RF sensitivity. The factory default position for this jumper is the
Distance (DX) setting, configuring the receiver for maximum sensitivity.
This is the appropriate setting for most applications (to allow for
maximum reception range). However, if multiple AT900-32 transmitters
are to be used in a common area (so as to broadcast multiple audio
programs), and any are set to operate on numerically adjacent channels,
there is a possibility of interference from one channel to the adjacent
channel. Switching the jumper to the LOCAL setting on any receiver(s) that
exhibit such interference may reduce or eliminate this interference. To do
this, perform the following steps:
1. Locate the LOCAL/DX jumper on the circuit board. In its factory
default position, the jumper connects the middle pin of the 3-pin
group to the DX pin, leaving the LOCAL pin open.
2. Remove the jumper from its default position, and reinsert it such
that it connects the middle pin to the LOCAL pin (leaving the DX pin
open).