User’s Guide – 900MHz Stereo Audio Transmitter & Receiver
13
Noise Reduction (Transmitter and Receiver)
The transmitter and receiver are each equipped with active noise
reduction circuits that minimize objectionable background noise
(or “hiss”) which might otherwise be noticeable during periods of
silence, such as the pause between tracks on a CD. These circuits
are normally enabled (factory default). However, if the particular
audio source material has very few (if any) silent pauses, the noise
reduction circuits may be turned off, to give the sound a somewhat
“brighter” or “livelier” character.
To de-activate the noise reduction circuits, locate the
NR
switches
on the transmitter and receiver printed circuit boards. Slide the
actuator of each switch to its
NR OFF
position.
For the AT900-32D remote antenna models, the Noise Reduction
switch will be found in the controller (aluminum extrusion).
Note 1:
Be sure to readjust the transmitter’s audio modulation
level (as described on pages 6and 7) anytime the noise reduction
circuits and/or ALC are either activated or turned off.
Note 2:
The noise reduction switches in the transmitter and the
receiver must be set to match each other (either on or off), in order
to maintain balanced audio frequency response.
Automatic Level Control (Transmitter)
The AT900 Series transmitters have an ALC control circuit to help
prevent under or over modulation as a result of dramatic changes
in source volume. The factory default is ALC ON. To turn the
ALC feature off, use the slide switch located on the transmitter
board also located inside the aluminum extrusion case.
14
Applied Wireless, Inc.
Technical Specifications
AT900-32 Transmitter
Operating Frequency (32 Channels)
902 – 928 MHz
Operating Voltage Range
7.5 to 18VDC
Operating Current
120 mA
Audio Signal-to-Noise Ratio*
78 dB
Audio Frequency Response (+/-3dB)*
50 - 15,000 Hz
Audio Channel (L/R) Separation (@ 1KHz)*
30 dB
Audio Distortion (@ 1kHzm +/-25KHz deviation)*
0.3%
Stereo Pilot Level
-20 dBc
RF Output Power
1 mW (0 dBm)
Frequency Stability (over operating temp.range)
+/-30 ppm
FM Deviation
+/-75 KHz
Harmonic Suppression
-45 dBc
Antenna Output Impedance
50 Ohms
Operating Temperature Range
-20
C to +70
C
Storage Temperature Range
-50
C to +150
C
*Audio performance specifications are “end-to-end” characteristics,
when used with Model AR900-32 receiver.
AR900-32 Receiver
Operating Frequency (32 Channels)
902 – 928 MHz
Operating Voltage Range
7.5 to 18VDC
Operating Current
140 mA
Audio Frequency Response (+/-3dB, flat EQ)*
50 - 15,000 Hz
Audio Channel (L/R) Separation (@ 1KHz)*
30 dB
Audio Signal-to-Noise Ratio*
50 dB
Audio Distortion (@ 1kHzm +/-25KHz deviation)*
0.3%
RF Input Sensitivity (30 dB SNR)
-106 dBm
IF Bandwidth
180 KHz
Antenna Input Impedance
50 Ohms
Frequency Stability (over operating temp. range)
+/-30 ppm
Operating Temperature Range
-20
C to +70
C
Storage Temperature Range
-50
C to +150
C
*Audio performance specifications are “end-to-end” characteristics,
when used with Model AT900-32 transmitter.
