Lectrosonics UCR100 - Manual (Page 4)

UCR100
LECTROSONICS, INC. 4
General Technical Description
Features
The multi-frequency UCR100 FM Receiver is designed
to operate with the Lectrosonics UM100 Transmitter and
features microprocessor control of 256 frequencies of
operation within each frequency block. Each block cov-
ers 25.5 MHz with 0.1 MHz frequency spacing. Any one
of ten different frequency blocks are factory available
from 537.6 MHz to 805.5 MHz (except 608 to 614 MHz).
The receiver’s unique microcontroller design provides
simple operation for audio level/limit LED monitor-
ing, RF level LED monitoring, squelch, easy on-the-fly
frequency programming and low battery warning. The
UCR100 Receiver uses 20 kHz FM deviation for ef-
ficient use of the bandwidth and dual band companding
for clean quiet audio. The receiver operates on one 9
Volt alkaline battery for up to 8 hours and features a
blinking LED low battery indicator. The voltages are
internally regulated for stability. The receiver is housed
in a compact, rugged, lightweight aluminum enclosure.
The unit features a durable integral swing-aside battery
compartment door.
Dual Band Compandor
Traditionally, compandors have been a source of distor-
tion in wireless microphone systems. The basic problem
with conventional systems is that the attack and decay
times are always a compromise. If the time constants
are fast, high frequency transients will not be distorted,
but this will cause low frequency distortion. If the time
constants are slower, low frequency audio distortion
will be low, but high frequency transients will then be
distorted.
The 100 system introduces the proven Lectrosonics ap-
proach to solving this basic problem, called “dual-band
companding.”
There are actually two separate compandors in the 100
system, one for high frequencies and one for low fre-
quencies. A crossover network separates the frequency
bands at 1kHz with a 6dB per octave slope, followed
by separate high and low frequency compandors. The
attack and release times in the high frequency com-
pandor are fast enough to keep high frequency tran-
sient distortion at a low level, and the low frequency
compandor uses slower time constants, reducing low
frequency distortion to well below that of a conventional
compandor.
Pre-Emphasis/De-Emphasis
The signal to noise ratio of the 100 system is extended
by utilizing pre-emphasis (HF boost) in the transmitter
and de-emphasis (HF roll off) in the receiver. Pre-em-
phasis and de-emphasis in an FM radio system usually
provides about a 10dB improvement in the signal to
noise ratio of the system, but the high frequency boost
in the transmitter must be removed in a purely comple-
mentary manner or else the frequency response of the
original audio signal will be altered.
The dual-band compandor in the 100 Series system
essentially provides a dynamic pre-emphasis/de-em-
phasis function with low distortion.
UCR100 Block Diagram