User's Manual

UHF Digital Hybrid Wireless
®
Rio Rancho, NM
7
SmartSquelch
™
A DSP-based algorithm called SmartSquelch
TM
optimizes
the receiver performance in very weak signal conditions.
The RF level and supersonic noise in the audio are con-
tinuously monitored to determine the appropriate noise
reduction needed and the point at which squelch (com-
plete muting of the audio) is necessary.
As the RF level decreases and supersonic noise in the
signal begins to increase, a variable knee, high frequency
roll-off filter is applied to suppress high frequency noise.
The filtering action moves in and out smoothly to avoid
abrupt changes that could be audible. When the RF signal
becomes so weak that the receiver can no longer deliver
usable audio, the squelch will activate.
SmartDiversity
™
Microprocessor controlled antenna phase combin-
ing is used for diversity reception. When the incoming
RF level drops to a certain point, the phase (polarity)
of one antenna is reversed and the resulting level is
compared with the one in the previous state. If the level
has increased, the phase is retained. If the level has
decreased, the phase is reversed back to the previous
state.
The logic behind this design is based upon the fact that
two antennas mixed in phase will deliver a stronger
signal than either antenna by itself. If the antennas are
spaced more than a few inches apart, the signals arriv-
ing at them will be non-correlated (diverse), to effec-
tively deal with multi-path dropouts.
Turn On and Turn Off Delays
A brief delay is applied when the receiver is powered up
or down to prevent audible noise such as a thump, pop,
click or other transient noise.
Test Tone
To assist in matching the audio levels of equipment con-
nected to the receiver, a 1 kHz audio test tone genera-
tor is provided, with an output level adjustable from -50
to +5 dBu in 1 dB increments.
The tone simulates the audio output with a steady sig-
nal at full modulation, making it easy to adjust the level
to precisely match the optimal level for the connected
device and maximize the signal to noise ratio of the
system.
LCD Display
Setup and monitoring is done through the LCD display
on the control panel. The built-in backlight for view-
ing in dimly lit environments can be set to remain on
for 30 seconds, 5 minutes or to remain on constantly.
The characters and background on the display can be
inverted as desired for easy viewing in brightly or dimly
lit environments.
Smart Noise Reduction (SmartNR
™
)
Note: The SmartNR setting is user selectable only in
the Digital Hybrid compatibility mode. In other modes,
noise reduction is applied in such a way as to emulate
the original analog system as accurately as possible
and is not user adjustable.
The wide dynamic range of digital hybrid technology,
combined with flat response to 20 kHz, makes it pos-
sible to hear the -120 dBV noise floor in the mic pre-
amp, or the (usually) greater noise from the microphone
itself. To put this in perspective, the noise generated
by the recommended 4k bias resistor of many electret
lavaliere mics is –119 dBV and the noise level of the mi-
crophone’s electronics is even higher. In order to reduce
this noise the receiver is equipped with a “smart” noise
reduction algorithm called SmartNR
TM
, which removes
hiss without sacrificing audio high frequency response.
SmartNR
TM
works by attenuating only those portions of
the audio signal that fit a statistical profile for random-
ness or “electronic hiss.” Because it is much more than
a sophisticated variable low pass filter, the transparency
of the audio signal is preserved. Desired high frequency
signals having some coherence are not affected, such
as speech sibilance and tones.
SmartNR
TM
algorithm has three modes, selectable
from a user setup screen. The optimal setting for each
application is subjective and is normally selected while
simply listening.
• OFF defeats noise reduction and complete trans-
parency is preserved. All signals presented to the
transmitter’s analog front end, including any faint
microphone hiss, will be faithfully reproduced at the
receiver output.
• NORMAL applies enough noise reduction to re-
move most of the hiss from the microphone preamp
and some of the hiss from lavaliere microphones.
The noise reduction benefit is significant in this
position, yet the degree of transparency maintained
is exceptional.
• FULL applies enough noise reduction to remove
most of the hiss from nearly any signal source
of reasonable quality and some high frequency
environmental noise, assuming the input gain is set
properly at the transmitter.