Applied Wireless AT900-32 User manual

Instructions for Installation and Operation
900 MHz Stereo Audio Receiver
Model AR900-32
900 MHz Stereo Audio Transmitter
Model AT900-32
Long Range Wireless Applications
User’s Guide

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User’s Guide – 900MHz Stereo Audio Transmitter & Receiver 1
900 MHz Stereo Audio Transmitter
Model AT900-32
900 MHz Stereo Audio Receiver
Model AR900-32
Introduction / Product Descriptions
Model AT900-32 from Applied Wireless, Inc. is a high quality transmitter
designed to broadcast excellent quality low noise stereo audio from any
line level source, to the Applied Wireless model AR900-32 receiver. The
AT900-32 transmitter is compatible with line level audio sources such as
CD and DVD players, commercial radio (AM or FM) receivers, satellite
radio receivers, MP3 players, and PCs. Model AT900-32 conforms to
FCC Part 15 requirements for unlicensed use, and will transmit over
distances up to 750 feet.* The range may be increased substantially
through the use of a directional antenna (such as a flat panel or Yagi) at
the receiver.
* Unobstructed, straight line-of-sight range, when used with the standard antennas
included with the transmitter and receiver.
The AT900-32 transmitter and the AR900-32 receiver provide thirty-two
user-selectable channels of operation within the 902 – 928 MHz band to
enable simultaneous operation of multiple transmitters in a common area.
Excellent frequency stability is assured through the use of crystal
references. The products incorporate precise FM modulation and
sophisticated filters to provide stable, interference-free high fidelity audio
reception.
The transmitter and receiver are housed in small yet rugged aluminum
extrusion enclosures. AC power converters (9VDC) are supplied, along
with RCA phono-type audio cables. By FCC regulation, the transmitter’s
quarter-wave antenna is permanently attached (substituting a different
antenna, or mounting the antenna remotely are not permitted). The antenna
supplied with the receiver is a removable quarter-wave ground plane
(sometimes referred to as a half-wave) antenna. The receiver’s antenna

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attaches with a BNC connector, enabling the use of an alternative antenna,
(such as a directional flat panel or Yagi) to increase operating range
(please contact Applied Wireless for a selection of available antennas).
The AT900-32 transmitter and the AR900-32 receiver are well-suited for
many diverse applications, including distribution of audio entertainment
content throughout a building, home theater installations, commercial and
industrial surveillance, monitoring, security, etc.
Installation Instructions
Before Beginning the Installation
Plan your installation carefully. The physical location and orientation of
the transmitter and receiver antennas (relative to each other and their
surroundings) will have a significant influence on reception quality at the
receiver. The following guidelines will generally yield the best results:
•Both the transmitter antenna and the receiver antenna should be
positioned vertically (pointing either up or down).
•Antennas should be positioned high enough to enable people to move
about below them without creating obstructions between the antennas.
•Although the RF signal from the transmitter will pass through most
non-metallic building materials (wood, stucco, brick, etc.), its strength
is reduced with every wall through which it must pass. Therefore,
maximum stated reception range is based on unobstructed line of sight
conditions.
•The transmitter and receiver are both rated for indoor use only. If
either unit must be located outdoors, it must be protected from the
elements (using, for example, a non-metallic NEMA4 enclosure).
Connecting Audio to the AT900-32 Transmitter
Connect a line level stereo audio source (outputs from a CD player, for
example) to the corresponding LEFT and RIGHT line-level input jacks on
the transmitter’s rear panel (refer to Figure 1). A shielded dual cable is
supplied with the transmitter for making these connections. Some audio
devices, such as MP3 players, portable CD players, and PC sound cards
have a single miniature (3.5mm) stereo phone jack (as opposed to separate

User’s Guide – 900MHz Stereo Audio Transmitter & Receiver 3
RCA phono-type jacks). To connect any of these to the transmitter, use the
supplied adaptor in conjunction with the standard dual cable to make the
connection.
Note 1: If the audio source device provides only a single (mono) output, a
“Y” adaptor (not supplied) may be used to feed the signal to both of the
transmitter’s input jacks.
Note 2: If a microphone is to be used as the audio source, an external
microphone preamp (not supplied) must be used to raise the microphone’s
output signal to the required line level.
Connecting the AR900-32 Receiver’s Audio Outputs
Using the shielded dual audio cable provided, connect the receiver’s line
level audio outputs to the appropriate inputs on the device that is to
amplify and reproduce (or record) the received audio signals (refer to
Figure 2). If the destination device has only a single (mono) input, a “Y”
adaptor (not supplied) may be used to combine the receiver’s LEFT and
RIGHT outputs, and feed the combined signal to the destination device’s
mono input jack.
Figure 1 – AT900-32 Transmitter (Rear Panel)

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Connecting Power to the Transmitter and Receiver
The AT900-32 and the AR900-32 each require an external power source
of between 7.5 and 18 volts DC. A plug-in 120VAC-to-9VDC power
converter is supplied with each unit. Insert the power converter’s 2.1mm
plug into the DC INPUT jack on the unit’s rear panel (refer to Figures 1 and
2). Plug each converter into a live 120VAC outlet. The transmitter’s red
POWER indicator LED (on the front panel) should illuminate. On the
receiver, power on is indicated by the illumination of the 2 digit CHANNEL
display.
User Settings and Adjustments
Selecting the Channel of Operation (Transmitter)
Referring to Figure 3 and Table 1, select the channel on which the
transmitter will operate. Available channels are numbered 01 through 32.
To select a channel, use a small flat-blade screwdriver to rotate the
selector on the left to the “tens digit” of the desired channel, then rotate
the selector on the right to the “ones digit” of the desired channel. As an
example, to select channel 26 rotate the selector on the left to “2,” and
rotate the selector on the right to “6.” Be sure to line up the selector’s
triangle-shaped pointer (NOT the screwdriver slot) to the desired number.
Please note that setting the channel to “00” is the same as channel “01.”
Similarly, setting the channel to any number from “33” to “99” is the same
as channel “32.”
If several AT900-32 transmitters are to be used simultaneously in a
common area (so as to broadcast multiple audio programs), each
transmitter must be set to its own unique channel.
Figure 2 – AR900-32 Receiver (Rear Panel)

User’s Guide – 900MHz Stereo Audio Transmitter & Receiver 5
Selecting the Channel of Operation (Receiver)
The AT900-32 provides 32 user-selectable channels. Referring to Figure 4
and Table 1, use the DOWN and UP buttons on the unit’s front panel to
select the desired channel. Momentarily pressing either button will raise or
lower the displayed channel by one; holding either button continuously
will rapidly cycle the channels up or down as appropriate. If multiple
AT900-32 transmitters are operating in a common area to broadcast
multiple audio programs, the AR900-32 receiver can receive any of the
desired programs simply by selecting the corresponding channel.
Figure 3 – AT900-32 Transmitter (Front Panel)
Set this selector
to the “tens” digit
of the desired
channel
Set this selector
to the “ones” digit
of the desired
channel
Figure 4 – AR900-32 Receiver (Front Panel)

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If you encounter sporadic noises, dropouts, fading, etc., it may be due to
interference from another 900MHz device (such as an older cordless
phone or baby monitor) operating nearby. To alleviate the problem, try
selecting a different channel for the transmitter and receiver – ideally one
that is at least 9MHz above or below the originally selected channel (see
Table 1).
Please note: Wireless devices that operate outside of the 902 – 928MHz
frequency band, such as modern cordless phones and computer networks
operating at 2.4 or 5.8GHz, will not generally interfere with, or be affected
by, the AT900-32 transmitter and/or the AR900-32 receiver.
Table 1 – Channel / Frequency Allocations
Channel
Number Frequency (MHz) Channel Number Frequency (MHz) Channel Number Frequency (MHz) Channel Number Frequency (MHz)
01 905.0 09 914.2 17 905.6 25 915.0
02 906.2 10 915.4 18 906.6 26 916.2
03 923.6 11 917.0 19 907.6 27 917.4
04 924.4 12 917.8 20 908.8 28 918.4
05 925.6 13 919.0 21 910.0 29 919.6
06 910.6 14 920.6 22 911.2 30 921.0
07 911.8 15 921.4 23 912.4 31 921.8
08 913.4 16 922.6 24 913.8 32 923.0
NOTE 1: Setting the transmitter to channel “00” is the same as channel 1. Similarly, setting the
transmitter’s channel to any number from “33” to “99” (inclusive) is the same as channel 32.
NOTE 2: If the AT900-32 and AR900-32 will be used along with an Applied Wireless video transmitter
and receiver (models VT900-3 and VR900-3), the channel for the audio units must be at least 9MHz
above or below the channel of the video units, to prevent interference between the RF signals. For
example, if the video units are set to channel 1 (907MHz), set the audio units to channel 32.
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.

User’s Guide – 900MHz Stereo Audio Transmitter & Receiver 7
IMPORTANT!
Properly setting the transmitter’s modulation level is
CRITICAL to satisfactory operation of the transmitter,
and receiver. If the level is set too low, the receiver will
likely be plagued with objectionable background noise
(hiss). If the level is set too high, distorted audio
and/or interference on adjacent channels is likely to
result.
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. MP3 player, portable CD player, or PC sound card) 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.

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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 output phono jacks.
EQualization (Receiver)
When headphones or earbuds are used with the receiver, the EQ button on
the receiver’s front panel may be used to select one of four preset audio
equalization (tone) profiles, enabling you to select the audio response
characteristics that you prefer. The chosen equalization profile only affects
the audio from the headphone jack on the rear panel. The audio signals at
the line level audio output phono jacks remain “flat” regardless of the
equalization profile chosen for the headphones.
Momentarily pressing the EQ button will cause the 2-digit CHANNEL
indicator to display the current equalization profile. The four equalization
profiles are as follows:
•E1: No Equalization (flat response)
•E2: Bass Boost
•E3: Treble Boost
•E4: Bass Boost + Treble Boost
Pressing the EQ button again (while the display is indicating the
equalization profile) will advance to the next profile. The 2-digit CHANNEL
indicator will automatically revert to displaying the receiver’s current
channel when the EQ button has not been pressed for two to three seconds.